Pregnancy Chances After Unprotected Intercourse: A Guide

Probability of Pregnancy

Hello, Doctor.
My menstrual cycle is usually around the end of the month.
My period in February was from February 20 to February 23, and in March, it was from March 28 to March 31.
I had unprotected intercourse with my boyfriend on April 4 (without a condom and without ejaculation), and I took emergency contraception the same day.
I experienced some bleeding from April 7 to April 10 (without the typical menstrual cramps).
Additionally, I had another risky sexual encounter on April 22 (without a condom and with external ejaculation), and I took another emergency contraceptive pill that day as well.
However, as of today (May 1), I have not experienced any bleeding or menstruation, only some premenstrual symptoms (lower abdominal cramps) starting around April 29.
Besides that, there are no other symptoms.

Could you please tell me if the bleeding from April 7 to April 10 was my period? If that was indeed my period, when would my ovulation likely have occurred? Will my next period also be around May 7? What is the likelihood of pregnancy from the unprotected intercourse on April 22 with external ejaculation? I took a pregnancy test on the morning of May 1, which came back negative, but I am worried that it might be too early to test accurately.
I have been experiencing abdominal pain for the past few days without any bleeding, and I only noticed slightly increased discharge on April 13 and April 27.
Thank you, Doctor!

wu, 10~19 year old female. Ask Date: 2024/05/01

Dr. Liu Fuping reply Obstetrics and Gynecology

Emergency contraception should not be used as a regular birth control method! Emergency contraceptive pills typically utilize high doses of progestin to disrupt the natural hormonal fluctuations in a woman's body, which means they suppress or delay ovulation to reduce the chances of fertilization.
Additionally, they increase the secretion of cervical mucus, which affects sperm motility.
Since the doses of estrogen and progestin in emergency contraceptive pills are 8 to 10 times higher than those in regular contraceptive pills, they can easily cause side effects such as nausea, vomiting, dizziness, and breast tenderness.
If used more than once within a month, it may lead to endocrine disturbances, such as irregular menstruation, resulting in increased menstrual flow or delayed periods, which may necessitate the use of medication to induce menstruation.
The probability of pregnancy from each act of intercourse is approximately 25%, which may decrease with age.
Due to the irregularities in menstruation, it is recommended to take a pregnancy test two weeks later.

Reply Date: 2024/05/01

More Info

Understanding the chances of pregnancy after unprotected intercourse can be quite complex, especially when factoring in the timing of ovulation, the use of emergency contraception, and individual menstrual cycle variations. Let's break down your situation step by step.

1. Menstrual Cycle and Ovulation: Your menstrual cycle appears to be around 28-31 days, which is typical for many women. Ovulation generally occurs about 14 days before the start of your next period. Based on your reported cycle, if your last period started on March 28, you would likely ovulate around April 11. This timing is crucial because the fertile window is typically a few days before and after ovulation.

2. Unprotected Intercourse and Emergency Contraception: You mentioned having unprotected intercourse on April 4 and again on April 22, with emergency contraception taken shortly after both instances. Emergency contraception (like Plan B) is most effective when taken as soon as possible after unprotected intercourse, ideally within 72 hours. Since you took the emergency contraceptive after both incidents, this significantly reduces the chances of pregnancy.

3. Bleeding After Emergency Contraception: The bleeding you experienced from April 7 to April 10 could be a side effect of the emergency contraception rather than your regular menstrual period. Emergency contraceptives can cause changes in your menstrual cycle, including spotting or bleeding that may not be a true period. It’s also possible that your next period could be delayed or altered due to the hormonal changes caused by the emergency contraceptive.

4. Pregnancy Testing: You mentioned taking a pregnancy test on May 1, which was negative. It’s important to note that testing too early can lead to false negatives, especially if you are testing before your expected period. If your cycle is regular and you expect your period around May 7, it would be advisable to wait a few more days and test again if your period does not arrive.

5. Risk of Pregnancy from April 22 Intercourse: The risk of pregnancy from the April 22 encounter is relatively low, especially since you took emergency contraception immediately afterward. However, if ovulation occurred around April 11, the likelihood of pregnancy from that encounter is minimal, as sperm can survive for up to five days in the female reproductive tract, but the egg is viable for only about 12-24 hours post-ovulation.

6. Symptoms and Next Steps: The abdominal pain you are experiencing could be related to hormonal fluctuations, the effects of the emergency contraception, or even premenstrual symptoms. If your period does not arrive by the expected date, consider retesting for pregnancy. If you continue to have symptoms or have concerns, it would be wise to consult with a healthcare provider for further evaluation.

In summary, while the chances of pregnancy from the encounters you described are low due to the use of emergency contraception, monitoring your cycle and symptoms is essential. If you have any further concerns or if your symptoms persist, seeking medical advice would be the best course of action.

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