There are different brands of the morning-after pill, and these have different modes of action. In a nutshell, the emergency contraceptive pill can work in any one of three ways. First of all, it can delay ovulation, altering a woman’s menstrual cycle. Secondly, it can inhibit ovulation, which means no egg is released from the ovaries. Thirdly, it can cause irritation to the lining of the womb, thereby inhibiting implantation. Whichever ways this pill works, all are designed to prevent fertilization and implantation of an egg, which could lead to pregnancy.
To understand more precisely how the morning-after pill works, it’s necessary to know how conception occurs. Fertilization is the union of a female egg with male sperm. This takes place in the fallopian tube, and the fertilized egg then makes its way down the fallopian tube, where it implants in the womb. Implantation allows the egg to grow and develop and it can take 5-7 days for a fertilized egg to travel down the fallopian tube to implant in the womb.
A woman usually ovulates every 28 days and, when the egg is released, it’s available for fertilization for 12-24 hours. Sperm entering a woman’s body can be capable of fertilizing an egg for up to 5 days on average. Emergency contraception takes about 12 to 24 hours to start working, and it remains effective for around 10 days.
The morning after pill will work in different ways depending on where a woman is in her monthly cycle. In nearly 80% of all cases, taking the emergency pill may not be necessary since a woman would not have been fertile. However, taking the emergency pill after an egg has been fertilized triggers the third mode of action described above. The pill alters the lining of the womb to make implantation impossible, and a woman’s body will reject the fertilized egg. This method is sometimes referred to as a chemical termination. However, those who advocate the emergency pill maintain it does not cause an abortion, arguing that the pill stops the pregnancy from happening in the first place. This argument assumes that pregnancy takes place upon implantation and not simply when an egg is fertilized. However, it is not always effective as there is still 1-2% that will still get pregnant from unprotected sex. This is where some people will turn to other options like abortion or go to private adoption agencies to make sure that they are not giving their child a poor start in life, but this is all the personal choice of the mother.
Preven and Levonelle (Plan B in the U.S.) are two of the most frequently used emergency contraception pills. Preven can stop or delay the release of an egg (ovulation), and it can prevent and egg from being fertilized by sperm if the egg has been released. Also, it can prevent a fertilized egg from implanting in the womb. Plan B can work by preventing the ovaries from releasing an egg. It can also prevent fertilization or stop an already fertilized egg from implanting.
Levonelle is the UK’s most common emergency contraceptive pill and a woman needs to take it within three days of unprotected sexual intercourse. Statistics show that the sooner a woman takes it, the more effective it is.
Factors that could prevent the emergency contraceptive pill from working properly include vomiting, having a high body mass index, taking other medication or having existing health complaints. Women should consult their GP if any of these apply.
In summary, the emergency contraceptive pill is only for emergency use and should not be used as a primary form of contraception.