Determining the Exact Conception Date in Early Pregnancy

If you are five weeks pregnant and want to know the exact date of conception, it is typically estimated to be about two weeks after the first day of your last menstrual period (LMP). Therefore, if you know the date of your last period, you can calculate the approximate

Due to a menstrual cycle of approximately 52 days, menstruation occurred on October 8.
There was unprotected external ejaculation with Male A on October 22, and internal ejaculation with Male B on October 25 and 30.
Pregnancy was confirmed on November 22 at five weeks.
I would like to ask the doctor if this pregnancy is likely from Male B.
Thank you, doctor.

Ms. Li, 30~39 year old female. Ask Date: 2022/11/24

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, you resemble type B, but it's not a hundred percent.
Wishing you good health.

Reply Date: 2022/11/24

More Info

Determining the exact conception date in early pregnancy can be quite complex, especially when there are multiple sexual partners involved and irregular menstrual cycles. In your case, with a menstrual cycle of approximately 52 days, it is crucial to understand how ovulation and conception work in relation to your cycle.

Typically, ovulation occurs about 14 days before the start of your next menstrual period. Given your last menstrual period (LMP) started on October 8, if we assume a 52-day cycle, your next period would be expected around November 29. This means that ovulation would likely occur around October 22, give or take a few days. Since you had unprotected intercourse with partner A on October 22, this date is significant because it aligns closely with your ovulation window.

Following that, you had intercourse with partner B on October 25 and 30. Sperm can live inside the female reproductive tract for up to five days, which means that if you ovulated on or around October 22, sperm from either partner A or partner B could potentially fertilize the egg. However, since you confirmed your pregnancy on November 22 and were estimated to be about five weeks along, this suggests that conception likely occurred around late October.

To narrow it down further, if we consider the timing of your sexual encounters and the lifespan of sperm, it is plausible that the conception could have occurred from the intercourse with partner B on October 25 or 30, especially since these dates are closer to the time of your confirmed pregnancy. However, it is also possible that the sperm from partner A could have fertilized the egg if ovulation occurred shortly after your encounter with him.

In conclusion, while it is difficult to definitively state which partner is the biological father based solely on the timing of intercourse, the likelihood leans towards partner B due to the timing of your sexual encounters relative to your ovulation. If you are seeking confirmation, a paternity test after the baby is born would provide a definitive answer.
It is also important to consider that irregular menstrual cycles can complicate the calculation of ovulation and conception dates. If you have concerns about your cycle or pregnancy, consulting with a healthcare provider for personalized advice and further evaluation is recommended. They can provide insights based on your medical history and any additional tests that may be necessary.

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