Nonhormonal and Emergency Contraception


Nearly half of all pregnancies in the United States (U.S.) are unintended.1 An unintended pregnancy occurs when no children (or no more children) were desired or if the pregnancy was mistimed, occurring earlier or later than desired.2 Since unintended pregnancies are often a surprise, patients may neglect prenatal care, resulting in poor outcomes for baby and mother. Adverse health outcomes may include lower birth weight, shorter duration of breastfeeding, increased postpartum depression risk, and increased parental stress.2

Unintended pregnancies pose an additional cost to the public health care system as well. In 2010, unintended pregnancy expenditures by Medicaid and other public health systems was an estimated $21 billion.2 About 95% of unintended pregnancies occur in women who do not use contraception or those who use it inconsistently or incorrectly.2 For pregnancies to be planned and desired, patients and their partners must be educated on proper contraceptive use to maximize their effectiveness. This activity will review nonhormonal contraceptive methods used to prevent pregnancy and the advantages and disadvantages of each method. Increasing access to the numerous contraceptive methods and providing guidance on correct and consistent use could help alleviate this public health crisis.3

Hormonal contraception is not for everyone. For many women, combined hormonal contraceptives—those containing estrogen and progestin—are not an option due to specific risk factors or contraindications. Other hormonal options, such as progestin only pills, depo-medroxyprogesterone, subdermal progestin implant, and progestin or copper intrauterine devices (IUDs), also may not be appropriate or desirable for some women. Even if women choose hormonal contraceptives as their primary contraception, those become inappropriate at different times in their lives. For example, there are times when women may require nonhormonal contraception as a backup method (i.e., after missed doses of hormonal contraception or in the event of a drug-drug interaction).

For some women, the easy access and relatively low cost of nonhormonal contraceptive methods are important. Even if no contraindications or precautions exist with hormonal options, some women may choose to avoid the adverse effects associated with estrogen- or progestin-containing products. Some nonhormonal methods also offer protection against sexually transmitted diseases (STDs) and sexually transmitted infections (STIs), including human immunodeficiency virus (HIV). If women do not engage in sexual intercourse regularly or only want to use birth control on an as-needed basis, this method is a nice option. Patients and providers should evaluate each product’s advantages and disadvantages to determine which one best fits the patient’s unique needs and lifestyle.


The concept of fertility awareness-based methods is to track the menstrual cycle to estimate the timing of ovulation during each cycle to estimate when the woman is fertile.4 These methods do not involve a chemical or barrier to prevent conception. Instead, women monitor their cervical mucus, basal body temperature, and/or menstrual cycle length to determine the fertile period. During the fertile period, women should abstain from intercourse or utilize another form of contraception to prevent pregnancy.

Women may choose fertility-based awareness methods because they pose no health risk to mother or fetus if pregnancy should occur, and they are typically low in cost.4 Others may choose this method for religious purposes or simply due to a lack of knowledge about other methods.4 Some disadvantages to these methods include lower efficacy compared to other methods, the need for abstinence or other contraception during the fertile period, and no STI or STD protection.4 In addition, some fertility awareness-based methods are time consuming. Examples of fertility awareness-based methods include

  • calendar-based methods
  • cervical mucus tracking
  • the symptothermal method
  • the lactational amenorrhea method

Calendar-Based Methods

Women who use calendar-based methods use their menstrual cycle length coupled with the survival of the ovum (24 hours) and the sperm (up to 5 days) to predict the fertile window.4 Since women’s menstrual cycles can vary in length, it is recommended to track 6 to 12 cycles before determining the average cycle length.4

There are 2 types of calendar methods: the Calendar Rhythm Method and the Standard Days Method. For the Calendar Rhythm Method, women calculate the first fertile day of the menstrual cycle by subtracting 18 from the number of days in their shortest cycles. They calculate the last fertile day by subtracting 11 from the number of days in their longest cycles.4 Women with irregular cycles should not use this method. The following example explains how women use the Calendar Rhythm Method.

Case: A woman plots her cycles for 6 cycles in a row and finds that her longest cycle was 28 days and her shortest cycle was 26 days. Her first fertile day would be cycle day 8 because 26 - 18 = 8. Her last fertile day would be cycle day 17 because 28 - 11 = 17. Based on these calculations, the woman should abstain from intercourse on days 8 through 17 of her menstrual cycle.

The Standard Days Method is a simpler calendar-based method recommended only for women with cycles between 26 and 32 days in length.4 This method recommends a woman avoid intercourse on cycle days 8 through 19 or use another method of contraception during this time.4

Cervical Mucus Methods

During ovulation, cervical secretions (referred to as cervical mucus) change to create an environment that helps sperm travel through the cervix, uterus, and fallopian tubes. By recognizing these changes in cervical mucus, a woman can pinpoint when she will ovulate and most likely be fertile.5 Women who utilize cervical mucus methods to prevent pregnancy carefully observe cervical mucus patterns during the menstrual cycle. They should seek advice from trained clinicians to help ensure proper interpretation of mucus.

Just before ovulation, the amount of mucus made by the cervix noticeably increases and the mucus becomes thin and slippery due to an increase in estrogen.5 Just after ovulation, the amount of mucus decreases, and it becomes thicker due to the rise in progestin.5 About 5 to 6 days before ovulation, women will note that cervical mucus is clear with consistency resembling raw egg whites.4 The last day that women note this mucus consistency tends to be within a day of ovulation, so this is referred to as the “peak symptom”.4 Women are considered fertile from the first day mucus is detected until 4 days after appearance of the peak symptom, during which time they should avoid intercourse.4

There are two major types of cervical mucus methods: Billings Ovulation Method and the TwoDay method. Women utilizing the Billings Ovulation Method observe their cervical mucus daily and chart its character and quantity noting any changes to track the fertile period. The TwoDay Method is an altered version of the Billings Ovulation Method where women track their cervical mucus daily and note if there were any secretions that day or the day before. If women note secretions on either day, they are likely fertile.4 If there are no secretions, she is likely to be infertile.4 This method is much simpler since it does not require a daily log of mucus changes.

Symptothermal Method

The symptothermal method combines the cervical mucus method and tracking basal body temperature. Women observe the cervical mucus to identify fertile period onset and use basal body temperature charting to identify the end of the fertile period.4 In most women, basal body temperature drops slightly 12 to 24 hours before ovulation and increases during ovulation at least 0.4°F above the lowest recorded temperature.4 Once a woman records at least 3 to 4 consecutive days of this sustained elevated temperature, they enter the infertile period.4

Women can take their basal body temperature rectally, vaginally, or orally but they must use the same site every day and record it at the same time every morning before getting out of bed.4 They must also use a thermometer calibrated to measure in increments of 0.1°F. This method is not effective for those women who do not experience this dip in basal body temperature. Women who are perimenopausal or have inadequate sleep patterns, stress, or infections are not optimal candidates for tracking basal body temperature.4

The Natural Cycles smartphone app to track basal body temperature is the only app U.S. Food and Drug Administration (FDA) cleared as a contraception method.6 Women can use this app to prevent, plan, or follow a pregnancy. Women track their basal body temperature each morning in the app, and the app’s algorithm makes fertility predictions each day. Depending on where the user is in her cycle, she will either get a green day (not fertile) or a red day (fertile). Natural Cycles is most effective for women with regular menstrual cycles, between 21 and 35 days in length.6 Women can use this contraceptive method alone or in conjunction with the symptothermal method, although using the app alone does not provide the same level of effectiveness in preventing pregnancy.7

Lactational Amenorrhea Method

When a mother is not menstruating while breastfeeding an infant younger than 6 months of age (providing at least 90% of nutrition), the lactational amenorrhea method (LAM) offers protection against pregnancy.4 This method is widely accepted as a natural family planning option immediately following birth. Benefits include breastfeeding encouragement and no requirement for a period of abstinence during the month.

Suckling by the infant causes a reduction in gonadotropin releasing hormone from the hypothalamus. This downregulates anterior pituitary gland release of follicle stimulating hormone and luteinizing hormone (LH), causing amenorrhea (absence of menstruation).8 If a woman is exclusively pumping breast milk for her child, this method is ineffective since the suckling action does not occur.4 For highest efficacy of LAM, experts recommend that the infant be less than 6 months of age and exclusively breastfed, and the mother should not be menstruating.8 Once supplemental feedings (i.e., with formula or solid food) begin, the efficacy rate decreases significantly.4 For women who are amenorrheic and continue to breastfeed exclusively beyond 6 months, this method may still be effective. Studies have shown it is still effective at 1 year postpartum, although efficacy decreases slightly (94% versus 98%).8

Compared with other nonhormonal and hormonal contraceptives, the risk of pregnancy with fertility awareness-based methods is higher, especially when used alone. Relying on a single fertility awareness-based method is not recommended. Patients should use a combination of methods that identify preovulatory and postovulatory changes, such as the symptothermal method.4 Additionally, fertility awareness-based methods do not protect against STDs and STIs and should, therefore, only be used in monogamous relationships.

Effectiveness of each method discussed can be found in Table 1.

Table 1. Effectiveness of Fertility Awareness-Based Contraceptive Methods4,7
Method Typical Use* Perfect Use*
No method 85% 85%
Calendar Rhythm Method 15% to 19% 3%
Standard Days Method 12% 5%
Billings Ovulation Method 8% 5%
TwoDay method 14% 4% to 6%
Symptothermal method 2% 0.4%
Natural Cycles app 7% 2%
Lactational amenorrhea method (for 6 months postpartum) 2% to 3% 0.5%
*Accidental pregnancy rate within 1st year of use



Condoms are an effective method of birth control and one of the few contraceptives that also protect against STIs and STDs. There are a wide variety of condoms on the market, including both male and female condoms.

Male Condoms

Male condoms create a mechanical barrier, preventing direct contact of the vagina with semen, genital lesions, and infectious secretions. Male condoms can be made of latex, non-latex products containing polyurethane or polyisoprene, or lamb cecum.4 Most condoms are made of latex, which is impermeable to viruses and offers protection against STDs and STIs, including HIV.4 Individuals cannot use latex condoms with oil-based lubricants, as oil can decrease the barrier strength of latex. If a lubricant is desired, water-soluble options are preferred.

Non-latex condoms also offer protection against STDs and STIs, including HIV. Polyurethane condoms are not subject to degradation by oil-based products, but patients using polyisoprene condoms must use a water-soluble product if lubrication is desired. Lamb cecum condoms are labeled only for pregnancy prevention, not STI or STD prevention, because pores in the membrane may allow passage of viral organisms.4 These condoms are not degraded by oil-based lubricants, and they are usually more expensive than latex condoms.

Studies have found that non-latex condoms have a significantly higher breakage rate versus latex condoms and have also been reported to have higher pregnancy rates.4 Therefore, latex condoms are the preferred choice when recommending male condoms. Non-latex condoms should be reserved for individuals with allergy or intolerance to latex. Table 2 provides tips for proper male condom use.

Table 2. Tips for Proper Use of a Male Condom4
  • Use unopened condoms within the expiration date that have been stored in a dry, cool place
  • Do NOT test the condom for leaks before using
  • Long fingernails or jewelry may easily tear condoms
  • Place condom on before the penis comes into any contact with the vagina
  • Leave ½ inch of space between the end of the condom and the tip of the penis if not using a reservoir-tipped condom
  • Hold the rim of the condom as you withdraw post ejaculation
  • Check the condom for tears before discarding

Female Condoms

The only female condom available is a second-generation condom known as the FC2, which is made of nitrile, a synthetic latex.9 Patients with a latex allergy can safely use this condom. Properly positioned, the ring at the closed end covers the cervix, and the sheath lines the walls of the vagina. The outer ring remains outside the vagina, covering the labia. The breakage rate for the female condom is lower than that of male latex condoms. However, slippage rates may be higher, especially with initial use, which may explain its lower efficacy for pregnancy prevention compared to male latex condoms.4

The female condom is an effective barrier to sexually transmitted bacteria and viruses and is similar in efficacy to latex male condoms for decreasing the risk of STDs and STIs, including HIV.4 Women may complain of a squeaking noise while using the female condom, which can be eliminated with oil- or water-based lubricants.4 Table 3 compares the advantages and disadvantages of male and female condoms, which may be useful when helping patients choose between the two options. Patients should never use male and female condoms at the same time, as increased friction could cause female condom displacement.4

Table 3. Male Latex Condom Versus Female Condom4,9
Method Advantages Disadvantages
Male latex condom • Inexpensive
• Provides protection from STDs and STIs, including HIV
• More effective than female condoms
• Higher breakage rate
• Contraindicated with latex allergy
• Efficacy decreased by oil-based lubricants
Female condom • Can be inserted prior to intercourse
• Provides protection from STDs and STIs, including HIV
• Can be used with latex allergy
• Can be used with oil- or water-based lubricants
• Outer ring may be uncomfortable
• Squeaking noise during intercourse
• More expensive than male condoms
• Less effective than male condoms
HIV = human immunodeficiency virus; STD = sexually-transmitted disease; STI = sexually-transmitted infection


A diaphragm is a reusable dome-shaped rubber cap with a flexible rim that women insert vaginally. It fits over the cervix to decrease sperm access sperm to the egg. The traditional diaphragm required a prescription from a clinician who would fit the patient for the correct size. Using a spermicide with this traditional diaphragm is recommended to enhance effectiveness.

An FDA-approved single-size, non-latex diaphragm is available by prescription in the U.S. A pelvic examination or traditional diaphragm fitting is not a requirement. However, if patients are concerned about whether the product will fit, it is recommended that a prescriber “test fit” the diaphragm. Patients can use this new product with the provided spermicidal gel to offer triple safety. The diaphragm itself provides a mechanical barrier, and the specialized gel forms a cellulose gel-like layer that acts an additional physical barrier in front of the cervix.10 Additionally, the gel has an acidic pH of 3.8 that allows for sperm immobilization.10

Women can insert the single-size diaphragm up to 2 hours before intercourse (up to 6 hours with the traditional diaphragm), and they must leave it in place for at least 6 hours after. However, leaving it in place for more than 24 hours is not recommended due to the potential for TSS.10 In the event of repeated sexual intercourse, women should apply extra gel in front of the diaphragm without removing it. The manufacturer recommends that women replace this diaphragm after 2 years of use.10 Diaphragms do not protect against STDs or STIs, so sexual partners should use condoms if they desire additional protection.

Cervical Cap

Smaller than a diaphragm, a cervical cap is a bowl-shaped device that fits snugly over the cervix like a thimble to block sperm entry. The only cervical cap available in the U.S. is a latex-free silicone cervical cap. It is available in 3 sizes and requires proper fitting by a clinician to select the correct size.11 Women using a cervical cap should fill it with spermicide prior to insertion. They can insert it 6 hours prior to intercourse, and they should not remove the cap for at least 6 hours after intercourse. A cervical cap can remain in place for multiple episodes of intercourse without adding more spermicide, but women should not wear it for more than 48 hours at a time to reduce TSS risk. Cervical caps do not protect against STIs or STDs.


Vaginal Spermicides

Spermicides are chemical surfactants that immobilize and destroy sperm cell.4 The only chemical spermicide available in the U.S. is nonoxynol-9, and it is available in many formulations, including films, foams, gels, and suppositories.4 Vaginal spermicide products do not protect against HIV and other STDs and STIs. Based on their low efficacy, women should not use them alone, but they may be a good choice for women requiring a backup method. 

Vaginal irritation may occur if these products are used frequently or if patients use highly-concentrated products, which may put users at an increased risk for infection.4 Each vaginal spermicide product has a unique application method, including required timing around intercourse, and onset and duration of action. Spermicidal gels provide the most lubrication during intercourse.4 Foam formulations distribute more evenly and adhere best to the cervical and vaginal areas. Spermicidal suppositories may require refrigeration, and sometimes their incomplete dissolution in the vagina can result in a “gritty” sensation. Vaginal films are the least messy and provide the longest duration of action, but they are also the most difficult to use.4

Contraceptive Sponge

The available vaginal contraceptive sponge has a dual mechanism of action. It contains the spermicide nonoxynol-9 to kill sperm and acts as a mechanical barrier by covering the cervix and absorbing semen.4 It has a concave dimple on 1 side to fit over the cervix and a loop on the other side to facilitate removal. Women must be able to locate the cervix with a reasonable degree of competence for correct sponge placement. 

Women can insert the sponge into the vagina up to 6 hours before intercourse, and it provides protection for 24 hours, regardless of the frequency of intercourse.4 After intercourse, women must leave the sponge in place for at least 6 hours before removal. However, they should not leave it in the vagina for more than 30 hours due to the potential to develop toxic shock syndrome (TSS).4 TSS is a rare, potentially life-threatening condition that arises from tampons or other materials left in place too long. These materials promote favorable conditions for growth of bacteria that release toxins in the vagina. Refer patients to the pharmacist if patients express signs and symptoms of TSS, including12

  • Vomiting
  • Diarrhea
  • Fever
  • Rash (sunburn-like)
  • Low blood pressure
  • Muscle pain

Women should make certain to remove the entire sponge after intercourse, since any remaining material may be a source of bacterial infection. They should discard the sponge after removal and never reuse the same sponge. Women who have given birth previously have a significantly higher pregnancy rate while using the sponge compared with women who have never given birth.4 This may be related to a poor fit in women who have delivered vaginally. For this reason, women who have given birth and women with an anatomical abnormality of the vagina should utilize alternative birth control.4 The contraceptive sponge does not protect against STIs and STDs, including HIV.

Hormone-Free Vaginal Gel

In May 2020, FDA approved a first-of-its-kind, hormone-free vaginal gel contraceptive containing lactic acid, citric acid, and potassium bitartrate.13 Hormone-free vaginal gel (HFVG), reduces sperm motility by affecting vaginal pH. When semen (sperm-containing ejaculatory fluid) enters the vagina, it alkalinizes the environment to improve mobility through the reproductive tract. This gel maintains normal vaginal pH (around 4.5 or lower) and reduces sperm motility, lowering the chance of sperm reaching the egg.13 Women should administer the contents of a single prefilled applicator vaginally immediately before or up to 1 hour before each act of intercourse.13 The gel is ineffective when administered after intercourse.

This vaginal gel’s most common adverse reactions are vulvovaginal burning and pruritis. Some males may experience local discomfort (e.g., burning, itching) but it is usually mild.13 Women can use this product any time during the menstrual cycle, and they can use it concomitantly with hormonal contraceptives, condoms (latex or polyurethane), and vaginal diaphragms. It is not recommended for use with vaginal rings.13 Women can also use this contraceptive with products for vaginal infections, including metronidazole, miconazole, or tioconazole.13 Women with a history of recurrent urinary tract infections or urinary tract abnormalities should not use this product, and it does not protect against STDs or STIs.13

Nonhormonal birth control methods each have a unique place in therapy depending on the needs, preferences, and lifestyle of women and their partners. Many factors should be carefully considered before choosing a contraceptive method including cost, ease of use, comfort with the method, and effectiveness (see Table 4).

Table 4. Effectiveness of Nonhormonal Contraceptive Methods4,14,15,16
Method Perfect Use* Typical Use*
Cervical cap 2 13
Condoms, male (latex) 2 13
Condoms, female 5 21
Contraceptive sponge** 9 14
Diaphragm 8 18
Hormone free vaginal gel 7 14
Spermicides alone 16 21
*Percentage of women with pregnancy in 1st year of use; ** Reported in women who have never given birth


Emergency contraceptives available in the U.S. include emergency contraceptive pills—combined hormonal contraceptives, levonorgestrel, and ulipristal acetate—and the copper IUD. Each product differs in regard to the mechanism of action, adverse effects, directions for use and effectiveness.

Combined Hormonal Contraceptives

Clinical trials have extensively studied ethinyl estradiol and levonorgestrel for use as emergency contraception.17 The combination of hormones used for this purpose is sometimes called the Yuzpe method after the Canadian physician who first described the regimen.17

The Yuzpe method requires patients to take 2 doses 12 hours apart of 100 to 120 mcg ethinyl estradiol and either 0.5 to 0.6 mg levonorgestrel or 1 to 1.2 mg norgestrel.18 There are currently no products available in the U.S. that contain these dose combinations marketed as an emergency contraceptive. However, providers can prescribe available combined hormonal birth control tablets in specified combinations to obtain the correct dosing utilized in the Yuzpe method. Technically, any brand of combined oral contraceptives can be used if it provides the right amount of hormones.

Adverse effects of the Yuzpe method include abdominal pain, breast tenderness, dizziness, fatigue, headache, and nausea/vomiting (which is significantly higher than with other regimens).18 A meta-analysis compared emergency contraceptive interventions and found that the Yuzpe method was less effective and produced more adverse effects versus levonorgestrel alone.19 However, researchers recommended that it remain an option for those with no other access to emergency contraception.19


The only progestin studied for freestanding use as an emergency contraceptive is levonorgestrel, and various other brand names.17 The original treatment schedule was 0.75 mg within 72 hours after unprotected intercourse and a second 0.75 mg dose 12 hours after the first dose. The progestin-only emergency contraceptive products now available in the U.S. provide a single 1.5 mg dose, as studies showed that a single 1.5 mg dose is as effective as the original 2-dose regimen.17

Levonorgestrel’s primary mechanism of action as emergency contraception is the inhibition or delay of ovulation.20 When taken before the start of the LH surge that precedes ovulation, levonorgestrel can blunt or eliminate it, depending on the timing of the dose, and prevent follicular rupture. Research has also linked this LH surge inhibition to failure of sperm to be able to fertilize the ovum. The drug quickly increases the thickness of cervical mucus to prevent sperm from passing through the cervix.20 If levonorgestrel use is delayed and the fertilization process has already started, it may be too late to be effective.20

Adverse effects of levonorgestrel emergency contraceptive include abdominal pain, abnormally heavy or prolonged menstruation, and nausea.20 In cases where the normal menstrual period is delayed for greater than a week after using this product, women should test for pregnancy.

Ulipristal Acetate

The second-generation anti-progestin ulipristal acetate partially blocks progesterone signaling at the ovaries to delay follicular rupture, thereby inhibiting or delaying ovulation.21 Like levonorgestrel, it exerts its primary contraceptive action prior to ovulation. However, it is unique in that it can still be effective after the LH surge has begun but prior to ovulation.22 Ulipristal’s adverse effects include abdominal pain, dysmenorrhea (menstrual cramps), nausea, and suppressed menstruation (usually at least 7 days later than expected).21 Patients should consider the possibility of pregnancy if menstruation is delayed for greater than a week after the expected menstrual period.

Copper Intrauterine Device

Since implantation occurs 6 to 7 days following ovulation, a provider can insert a copper IUD as an emergency contraceptive within 5 days of the first act of unprotected sex.23,24 It may also be inserted beyond 5 days of unprotected intercourse if it has not been more than 5 days since ovulation.24 For example, if a woman had unprotected intercourse 3 days before ovulating, technically the IUD could prevent pregnancy if inserted up to 8 days after intercourse. Because of the difficulty in determining the day of ovulation, however, many protocols recommend insertion up to only 5 days after unprotected intercourse.

The copper in the IUD works to prevent pregnancy by interfering with sperm transport and fertilization of an egg.24 Device insertion may be associated with mild-to-moderate pain and cramping or backaches for a few days after placement. The IUD can be removed if it is not intended to be used for long-term birth control. FDA has not approved the copper IUD for emergency contraception. However, the American College of Obstetricians and Gynecologists and Centers for Disease Control and Prevention both recommend it for emergency contraception.25

The nausea that emergency contraception causes can lead to vomiting, which can affect the drugs’ effectiveness. The dosing regimens and actions to take if vomiting occurs with each method are listed in Table 5 and Table 6 compares the efficacies emergency contraceptive methods. The copper IUD has the highest effectiveness, but this may not be the most convenient for women without access to a physician.

Table 5. Emergency Contraceptive Dose Timing and Recommendations for Vomiting18,20,21,24
Method Dosing Window Vomiting Recommendations
Combined hormonal contraceptive As soon as possible but within 72 hours of unprotected intercourse Repeat if vomiting occurs within 2 hours
Levonorgestrel As soon as possible but within 72 hours of unprotected intercourse Repeat if vomiting occurs within 2 hours
Ulipristal acetate As soon as possible but within 5 days of unprotected intercourse Repeat if vomiting occurs within 3 hours
Copper IUD Within 5 days but may be inserted beyond 5 days of unprotected intercourse if not less than 5 days after ovulation N/A
Table 6. Efficacy of Emergency Contraceptives25,26
Method Efficacy
Combined hormonal contraceptive 74%
 Within 24 hours of unprotected sex
 More than 24 hours after unprotected sex

Ulipristal acetate 98% to 99%
Copper IUD 98% to 100%

Clinical Considerations

Controversy: Is Implantation Prevented?

The use of levonorgestrel as emergency contraception continues to generate controversy. Much of this debate stems from whether it prevents fertilized eggs from implantation. FDA labeling also creates confusion. The product label reads that, in addition to its primary mechanism of action, this product may inhibit implantation by altering the endometrium. As birth control taken over a continuous period, levonorgestrel can alter the endometrial lining, and this is where the confusion may lie. As an emergency contraceptive at this single dose, research shows it has no effect on the endometrium, so it cannot prevent implantation of a fertilized egg.27,28 This may explain why levonorgestrel is not 100% effective at preventing an unintended pregnancy, as well as why it is less effective as time goes on after unprotected intercourse.

The FDA labeling for ulipristal acetate also indicates it may prevent implantation. However, research has demonstrated that ulipristal in the dosage used for emergency contraception does not affect embryo viability nor the implantation process.29 Research has also indicated that this emergency contraceptive is no more effective at preventing pregnancy than chance alone if used after ovulation.29

The effects of the copper IUD on implantation are a bit more difficult to discern. Research has suggested that copper’s main mechanism of action is to prevent fertilization through the effect of copper ions on sperm function. However, if fertilization has occurred, then copper can influence the receptivity of the endometrium.30 This may be due to the ability of copper ions to cause endometrial inflammation. Research seems conflicting on this issue since some studies have shown no effect on the endometrial lining.31 However, it is clear that methods used today exert their primary action by inhibiting ovulation or preventing fertilization.

Weight Considerations

Body weight influences the effectiveness of oral emergency contraceptive methods with efficacy declining as body mass index (BMI) increases.32 A 2011 analysis showed decreased efficacy for women with an increased BMI for both levonorgestrel and ulipristal.33 Among women with a BMI of 30 kg/m2 or higher, the failure rate was 5.8% for those using levonorgestrel and 2.6% for those using ulipristal.33 The authors suggested that ulipristal may be more effective than levonorgestrel for obese women. Ulipristal appeared to lose effectiveness at a higher BMI threshold of 35 kg/m2 as opposed to 25 kg/m2 with levonogestrel.33 

Some new evidence is emerging that may support doubling the dose of progestin-only emergency contraceptive pills in obese women.34 However, it is uncertain whether this approach would be effective, and it is currently not recommended. The most effective emergency contraception for overweight or obese women is the copper IUD since effectiveness is not affected by weight status.

Safety Concerns

Research shows that using emergency contraceptives remain safe if used repeatedly or more than once in the same menstrual cycle.35 No evidence exists that demonstrates emergency contraceptives lose their effectiveness when used repeatedly, and research shows no effect on future fertility.35 Experts recommend that women should be able to access and use emergency contraceptive pills as many times as needed. However, if faced with a chronic, repeat user it may be wise to recommend more effective, ongoing methods of contraception. It is also important to note that only barrier methods (e.g., condoms) protect against STDs and STIs, including HIV.


Considering the high rate of unintended pregnancies and their cost to society, there is a critical need for educating women about contraceptive methods. There are advantages and disadvantages of each nonhormonal contraceptive method with regards to cost, efficacy, and administration. Educating a woman to allow for an informed choice will result in a higher comfort level with the chosen method and one that fits her lifestyle and relationship status. Since research has shown emergency contraception to be safe with repeated use, a woman should not be limited to the number of times she has access to the various methods. However, an informed conversation about a more proactive approach to contraception may prove to be beneficial. Pharmacy technicians may be the first to intercept questions about nonhormonal contraceptives. Understanding the various products helps determine if women need pharmacist counseling for recommendation of an appropriate method.


  1. Finer LB, Zolna MR. Declines in unintended pregnancy in the United States, 2008–2011. N Engl J Med. 2016;374(9):843-852. doi:10.1056/NEJMsa1506575
  2. America’s Health Rankings: United Health Foundation. Unintended pregnancy. Accessed May 5, 2021.
  3. Dehlendorf C, Rodriguez MI, Levy K, et al. Disparities in family planning. Am J Obstet Gynecol. 2010;202(3):214-220. doi:10.1016/j.ajog.2009.08.022
  4. El-Ibiary S, Raney E. Prevention of Pregnancy and Sexually Transmitted Infections. In: Krinsky DL, Ferreri SP, Hemstreet BA, eds. Handbook of Nonprescription Drugs: An Interactive Approach to Self-Care. 20th ed. American Pharmacists Association; 2020.
  5. 5 The American College of Obstetricians and Gynecologists. Fertility awareness-based methods of family planning. Updated January 2019. Accessed May 5, 2020.
  6. NaturalCycles Nordic AB. Natural cycles user manual/instructions for use. March 2019. Accessed May 5, 2020.
  7. Pearson JT, Chelstowska M, Rowland SP, et al. Contraceptive effectiveness of an FDA-cleared birth control app: results from the Natural Cycles U.S. cohort [published online ahead of print, 2020 Dec 23]. J Womens Health (Larchmt). 2020;10.1089/jwh.2020.8547. doi:10.1089/jwh.2020.8547
  8. Tiwari K, Khanam I, Savarna N. A study on effectiveness of lactational amenorrhea as a method of contraception. Int J Reprod Contracept Obstet Gynecol. 2018;7(10):3946-3950. doi:10.18203/2320-1770.ijrcog20183837
  9. The Female Health Company. FC2: How to use. Accessed May 6, 2020.
  10. Caya. Caya contoured diaphragm. Accessed May 6, 2021.
  11. FemCap. Better birth control at your cervix. Accessed May 6, 2021.
  12. Schlievert PM, Davis CC. Device-Associated Menstrual Toxic Shock Syndrome. Clin Microbiol Rev. 2020 May 27;33(3):e00032-19. doi: 10.1128/CMR.00032-19. PMID: 32461307; PMCID: PMC7254860.
  13. Phexxi. Prescribing information. Evofem Biosciences, Inc.; 2020. Accessed May 6, 2021.
  14. Thomas MA, Chappel BT, Maximos B, et al. A novel vaginal pH regulator: results from the phase 3 AMPOWER contraception clinical trial. Contracept X. 2020;2:100031. doi:10.1016/j.conx.2020.100031
  15. Shihata A. The FemCap: a new contraceptive choice. Eur J Contracept Reprod Health Care. 1998;3(3):160-166. doi:10.3109/13625189809051420
  16. Schwartz JL, Weiner DH, Lai JJ, et al. Contraceptive efficacy, safety, fit, and acceptability of a single-size diaphragm developed with end-user input. Obstet Gynecol. 2015;125(4):895-903. doi:10.1097/AOG.0000000000000721
  17. Trussell J. Raymond EG, Cleland K. Emergency contraception: A last chance to prevent unintended pregnancy. January 2019. Accessed May 7, 2021.
  18. International Consortium for Emergency Contraception. Using oral birth control pills as EC. Accessed May 7, 2021.
  19. Shen J, Che Y, Showell E, et al. Interventions for emergency contraception. Cochrane Database Syst Rev. 2019;1(1):CD001324. doi:10.1002/14651858.CD001324.pub6
  20. Levonorgestrel (Systemic). Lexi-drugs. Riverwoods, IL: Lexicomp, 2021. Updated May 6, 2021. Accessed May 7, 2021.
  21. Ulipristal. Lexi-drugs. Riverwoods, IL: Lexicomp, 2021. Updated April 6, 2021. Accessed May 7, 2021.
  22. Fine P, Mathé H, Ginde S, et al. Ulipristal acetate taken 48-120 hours after intercourse for emergency contraception. Obstet Gynecol. 2010;115(2 Pt 1):257-263. doi:10.1097/AOG.0b013e3181c8e2aa
  23. Kibble J. Reproductive Physiology. In: The Big Picture Physiology: Medical Course & Step 1 Review. 2 ed. McGraw-Hill; 2020.
  24. Copper IUD. Lexi-drugs. Riverwoods, IL: Lexicomp, 2021. Updated December 13, 2020. Accessed May 7, 2021.
  25. The American College of Obstetricians and Gynecologists. Emergency Contraception. September 2015. Accessed May 7, 2021.
  26. Plan B Manufacturer’s Website. Accessed May 8, 2021 at
  27. Durand M, del Carmen Cravioto M, Raymond EG, et al. On the mechanisms of action of short-term levonorgestrel administration in emergency contraception. Contraception. 2001;64(4):227-234. doi:10.1016/s0010-7824(01)00250-5
  28. Peck R, Rella W, Tudela J, et al. Does levonorgestrel emergency contraceptive have a post-fertilization effect? A review of its mechanism of action. Linacre Q. 2016;83(1):35-51. doi:10.1179/2050854915Y.0000000011
  29. Li HWR, Resche-Rigon M, Bagchi IC, et al. Does ulipristal acetate emergency contraception (ella®) interfere with implantation? Contraception. 2019;100(5):386-390.
  30. Gemzell-Danielsson K, Berger C, Lalitkumar P. Emergency contraception — mechanisms of action. Contraception. 2013;87(3):300-308. doi:10.1016/j.contraception.2012.08.021
  31. Smith-McCune K, Thomas R, Averbach S, et al. Differential effects of the hormonal and copper intrauterine device on the endometrial transcriptome. Sci Rep. 2020;10(1):6888. doi:10.1038/s41598-020-63798-8
  32. Cleland K, Raymond EG, Westley E, Trussell J. Emergency contraception review: evidence-based recommendations for clinicians. Clin Obstet Gynecol. 2014;57(4):741-750. doi:10.1097/GRF.0000000000000056
  33. Glasier A, Cameron ST, Blithe D, et al. Can we identify women at risk of pregnancy despite using emergency contraception? Data from randomized trials of ulipristal acetate and levonorgestrel. Contraception. 2011;84(4):363-367. doi:10.1016/j.contraception.2011.02.009
  34. Edelman AB, Cherala G, Blue SW, et al. Impact of obesity on the pharmacokinetics of levonorgestrel-based emergency contraception: single and double dosing. Contraception. 2016;94(1):52-57. doi:10.1016/j.contraception.2016.03.006
  35. International Consortium for Emergency Contraception. Repeated use of emergency contraceptive pills: The facts. October 2015. Accessed May 8, 2021.

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