Determining Conception Date: Insights for Expecting Parents

Date of conception

Hello Doctor: My last menstrual period was on June 4 (cycle 28-30 days).
The app indicated ovulation on June 20 (fertile window from June 15 to June 23).
The expected date for my July period is between July 4 and July 7.
In May, I had unprotected intercourse daily (internal ejaculation) with my boyfriend, who has a thyroid condition, and there was no pregnancy.
At the end of May, my boyfriend started medication to improve his sperm ejaculation, which seems to have normalized.
In June, we also had daily unprotected intercourse, and on June 24, I had intercourse with my ex-boyfriend (with a condom).
On July 11, I tested positive for pregnancy, approximately five weeks, measuring 0.8 cm.
On August 17, the doctor said I was nine weeks along (but the app and my calculations suggest about ten weeks).
I experienced lower abdominal pain, headaches, back pain, and breast enlargement with tenderness starting June 22.
My question is, could the pregnancy be from the intercourse on June 24? My boyfriend and I are planning to get married, so we have not been using contraception and are looking forward to the baby, but I feel uncertain and helpless.
I hope you can help me clarify this.
Additionally, could you please estimate the conception date? Thank you, Doctor!

A, 20~29 year old female. Ask Date: 2021/08/18

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, it is possible to conceive around June 20th.
Wishing you good health.

Reply Date: 2021/08/18

More Info

Determining the conception date can be a complex process, especially when there are multiple sexual encounters around the time of ovulation. Based on the information you provided, we can analyze the situation step by step.

Your last menstrual period (LMP) was on June 4, and you have a typical cycle length of 28 to 30 days. This means that ovulation likely occurred around June 20, as indicated by your app. The "danger zone" for conception, which is the time when you are most fertile, would typically be from June 15 to June 23.
You mentioned that you had unprotected intercourse with your boyfriend daily, starting from late May, and that he began taking medication to improve his sperm quality. This is an important factor, as the health of sperm can influence the chances of conception. You also noted that you had a sexual encounter with a previous partner on June 24, but this was with a condom, which reduces the likelihood of sperm entering the vagina.

You took a pregnancy test on July 11, which indicated that you were approximately five weeks pregnant. This timing aligns with conception likely occurring around the time of ovulation. Given that ovulation typically occurs about 14 days after the first day of your last menstrual period, it is reasonable to conclude that conception most likely occurred between June 20 and June 24.

However, since you had unprotected intercourse with your boyfriend during your fertile window, it is difficult to pinpoint the exact date of conception. The sperm can survive in the female reproductive tract for up to five days, which means that intercourse on June 20 could lead to conception even if it occurred a few days later.
The ultrasound performed on August 17 indicated that you were approximately nine weeks pregnant, which would correspond to a conception date around late June. This further supports the idea that the conception likely occurred around the time of ovulation or shortly thereafter.

In conclusion, while it is challenging to determine the exact date of conception, it is most probable that the conception occurred between June 20 and June 24, with a higher likelihood of it being around June 20, given the timing of ovulation and the unprotected intercourse with your boyfriend.
As for your concerns about the pregnancy and the health of your baby, it is essential to maintain regular prenatal check-ups with your healthcare provider. They will monitor the development of your baby and address any concerns you may have. If you have any further questions or uncertainties, do not hesitate to reach out to your healthcare provider for personalized guidance and support. Congratulations on your pregnancy, and I wish you all the best as you prepare for this exciting new chapter in your life!

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