From the FDA Drug Label
However, treatment was not effective in postponing follicular rupture when administered on the day of LH peak. The Morning after pill, ulipristal acetate, does not provide a clear duration for how long it prolongs ovulation.
- The drug label does not provide a direct answer to the question of how long ovulation is prolonged.
- There is information on the effects of ulipristal acetate on ovarian activity and follicular rupture, but it does not specify the duration of ovulation prolongation 1.
From the Research
The morning after pill can delay ovulation by approximately 5-7 days on average, with the exact duration of delay varying between individuals and depending on when in the menstrual cycle the medication is taken. This delay is achieved through the postponement of the luteinizing hormone (LH) surge that triggers ovulation, giving time for sperm in the reproductive tract to die off before an egg is released, thereby preventing fertilization 2. The mechanism of action of oral emergency contraception, such as levonorgestrel and ulipristal acetate, is primarily through the delay of ovulation, and current evidence reveals that it is ineffective postovulation 3.
Some key points to consider when using the morning after pill include:
- The copper intrauterine device is the most effective method of emergency contraception, followed by ulipristal acetate and levonorgestrel, respectively 2
- Levonorgestrel may be less effective if taken very close to ovulation, while ulipristal acetate remains effective closer to ovulation time 4
- Women who weigh more than 75 kg or have a body mass index greater than 25 kg/m(2) may have a higher risk of unintended pregnancy when using oral levonorgestrel emergency contraception, and therefore ulipristal acetate or copper intrauterine devices may be preferable in this setting 3
- After taking emergency contraception, the next period might come earlier or later than expected due to the hormonal disruption of the normal cycle 5
It's essential to note that if ovulation has already occurred when taking the morning after pill, it won't prevent pregnancy, and the medication should be taken as soon as possible after unprotected intercourse for maximum effectiveness 6. Clinicians should consider several factors when helping women make informed medical decisions regarding emergency contraception, including access to the products, individual preference, timing since unprotected intercourse, body mass index or weight, and initiation or resumption of routine contraception 2.