The morning-after pill works by preventing ovulation (when an egg is released from the ovary), blocking fertilization of an egg or inhibiting implantation of a fertilized egg.
As it can take up to 6 days for fertilization to occur, the morning-after pill can be used up to 120 hours (5 days) after unprotected sex, depending on the type of pill. There are two types of pill available; levonorgestrel pills and ulipristal acetate pills.
Morning-after pills containing levonorgestrel such as Plan B One-Step and Next Choice One Dose have an 89% efficacy rate when taken within 72 hours (3 days) following unprotected intercourse. These pills can also be taken up to 120 hours after intercourse, however, albeit with a lower efficacy rate.
The pill ella (ulipristal acetate) provides 85% efficacy in reducing the risk of pregnancy when it is taken within 120 hours of unprotected intercourse.
It is important to note that the morning-after pill will not cause a woman to have an abortion and will not provide protection if there is unprotected sex shortly after taking the pill. Normal methods of contraception should be initiated or resumed.
Newer research suggests that pills containing the hormone levonorgestrel do not prevent implantation. It is unknown, however, if ulipristal acetate has this effect.
Which morning-after pill should I use?
Pills such as Plan B One-Step and Next Choice One Dose, which contain the hormone levonorgestrel, may be less effective in overweight women defined as those with a body mass index (BMI) greater than 25. For these women, the pill ella or an IUD (see below) might be a more effective option.1 However, ella loses its efficacy in women with a BMI greater than 35.
Plan B One-Step and Next Choice One Dose are available over the counter without age limitation, although there are some brands with a two-dose method that require a prescription for women 16 and younger. The pill ella requires a prescription in all circumstances. These pills range in price from $30 to $65.
Depending on the brand of birth control, a woman’s routine birth control pill can sometimes be used as emergency contraception under the direction of a health care provider.
Side effects of the morning-after pill
While the morning-after pill offers women a safe option to prevent pregnancy, it does have some disadvantages, including mild side effects and no protection against sexually transmitted diseases.
Temporary side effects of the morning-after pill include:
- Menstrual changes
- Breast tenderness
It is important to note that the morning-after pill loses efficacy if vomiting occurs within 2 hours of taking it; if vomiting occurs, an additional dose will be required. When the morning-after pill is used frequently, it can cause menstrual irregularities, such as irregular and unpredictable menses. There are other options available for consistent birth control.
While the morning-after pill is generally safe, some women should not take it. These women include those who have an allergy to the pill’s components, are taking medications such as barbiturates or St. John’s wort, or during pregnancy.
Fetal effects of ulipristal acetate are not known, and this pill is also not recommended to be taken by someone who is breastfeeding. Levonorgestrel during pregnancy is not harmful – although it will not be effective – as it is not an abortion-inducing medication.
If, after using the morning-after pill, you do not have a menstrual flow within 3-4 weeks, it is recommended that a pregnancy test be taken.
Contact our office if you have symptoms of an ectopic pregnancy or miscarriage, such as bleeding or spotting that lasts longer than a week, or severe lower abdominal pain 3-5 weeks after using the morning-after pill.
ParaGard IUD is 99.9% effective when inserted by our office within 120 hours (5 days) of having unprotected sex.
The additional benefit of ParaGard insertion is that in addition to providing emergency contraception, it also can provide effective birth control for up to 12 years.