The morning after pill, also known as emergency contraception, serves as a backup method to prevent pregnancy after unprotected sexual intercourse or contraceptive failure. It is not intended for regular use as a primary form of birth control. This medication can be used in situations such as a missed birth control pill, a condom breaking, or in cases of sexual assault. The effectiveness of the morning after pill is highest when taken as soon as possible after unprotected sex.
Understanding Ovulation and Conception
Ovulation is a regular process in the female reproductive cycle where a mature egg is released from the ovary. This typically occurs about midway through the menstrual cycle. After its release, the egg travels down the fallopian tube, where it remains viable for fertilization for approximately 12 to 24 hours.
Sperm can survive in the female reproductive tract for up to five days. If unprotected sex happens during this time, particularly around ovulation, there is a possibility of fertilization. Once fertilization occurs, the fertilized egg, now called a zygote, begins its journey to the uterus for implantation.
How Morning After Pills Intercept Pregnancy
Morning after pills primarily work by delaying or preventing ovulation, which is the release of an egg from the ovary. By interfering with this process, they aim to prevent the egg and sperm from meeting. There are two main types of morning after pills: levonorgestrel-based pills and ulipristal acetate-based pills.
Levonorgestrel-based pills, such as Plan B One-Step, contain a synthetic hormone similar to progesterone. This hormone works by temporarily stopping or delaying the release of an egg. These pills are most effective when taken within 72 hours (three days) of unprotected sex, though they can be used up to 120 hours (five days) later, with decreasing effectiveness over time.
Ulipristal acetate-based pills, like Ella, also delay or inhibit ovulation, and are effective for up to 120 hours (five days) after unprotected sex. They can do so even closer to the time of ovulation than levonorgestrel. This type of pill works by modifying progesterone receptors, which in turn disrupts the hormonal cascade necessary for egg release. Neither type of morning after pill will end an existing pregnancy.
Effectiveness in Relation to Ovulation
The effectiveness of the morning after pill depends significantly on where an individual is in their menstrual cycle, specifically in relation to ovulation. If ovulation has not yet occurred, both levonorgestrel and ulipristal acetate can be highly effective in preventing pregnancy by disrupting the ovulatory process.
However, if ovulation has already happened, the morning after pill’s main mechanism of action is no longer relevant. Once an egg has been released and is available for fertilization, or if fertilization has already taken place, these pills cannot prevent pregnancy. Therefore, taking the morning after pill after ovulation has definitively occurred offers no benefit in preventing pregnancy.
Ulipristal acetate may offer a slight advantage over levonorgestrel when ovulation is imminent, meaning the egg is about to be released. This is because ulipristal acetate can delay ovulation even when luteinizing hormone (LH) levels are rising, indicating that ovulation is very near. Despite this, neither pill can reverse an ovulation that has already taken place.
What to Do if Ovulation Has Occurred
If ovulation is believed to have already occurred, and emergency contraception pills like levonorgestrel or ulipristal acetate may not be effective, other options exist. The copper intrauterine device (IUD) is a highly effective form of emergency contraception that can be inserted up to five days after unprotected sex.
Unlike emergency contraceptive pills, the copper IUD primarily works by creating an environment hostile to sperm and eggs, preventing fertilization and implantation. The copper IUD can be effective even if ovulation has already taken place because its mechanism is not reliant on delaying egg release. It can also serve as a long-term birth control method once inserted.
Consulting a healthcare provider is important to discuss all available emergency contraception options and determine the most appropriate course of action, especially when considering the timing of ovulation.