Conception Dates: A Guide for Women - Obstetrics and Gynecology

I would like to confirm the date of conception?

Hello Doctor: My menstrual cycle is 30 to 33 days, with my last menstrual period starting on 10/28, 11/30, and 12/31, lasting about 7 days and ending on 1/17.
I had sexual intercourse without contraception on 1/26 and 1/28, with withdrawal method used, and with different partners.
According to an app, my ovulation day was indicated as 1/18 (ovulation period from 1/13 to 1/19).
My period was expected to start on 2/1 but has not arrived yet.
On 2/5, I took a home pregnancy test that showed two dark lines.
On 2/7, I went to the obstetrics and gynecology department and was found to have a gestational sac at 5 weeks and 3 days, with the estimated due date currently given as 10/8.
Considering whether to continue with the pregnancy, I would like to ask the doctor if the sexual intercourse on 1/26 and 1/28 could have resulted in conception? What would be the approximate date of conception?

Miss Wang, 20~29 year old female. Ask Date: 2022/02/07

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, it is more likely to be around the middle of the month, and less likely at the end of the month.
Wishing you good health.

Reply Date: 2022/02/07

More Info

Understanding conception dates and the menstrual cycle is crucial for women who are trying to conceive or avoid pregnancy. Based on the information provided, let's break down the details and clarify the concepts of ovulation, safe periods, and the likelihood of conception.

Menstrual Cycle Overview
A typical menstrual cycle lasts between 21 to 35 days, with an average of about 28 days. It consists of several phases:
1. Menstrual Phase: This is when menstruation occurs, lasting about 3 to 7 days.

2. Follicular Phase: Following menstruation, the body prepares for ovulation. Hormones stimulate the growth of follicles in the ovaries.

3. Ovulation: This is the release of an egg from the ovary, typically occurring around 14 days before the next expected period. For a cycle of 30-33 days, ovulation would likely occur between days 16 to 19.

4. Luteal Phase: After ovulation, the body prepares for a potential pregnancy. If fertilization does not occur, menstruation will begin again.

Calculating Ovulation and Safe Periods
In your case, with a menstrual cycle of 30-33 days, ovulation is estimated to occur around January 13 to January 19, based on the last menstrual period starting on December 31. The fertile window typically spans about 5 days before ovulation and the day of ovulation itself, making it crucial for understanding when conception is most likely.

Conception Likelihood
You mentioned having unprotected intercourse on January 26 and January 28. Given that your ovulation window was from January 13 to January 19, the likelihood of conception from those encounters is relatively low. Sperm can survive in the female reproductive tract for up to 5 days, but since your ovulation window had passed, the chances of the sperm fertilizing an egg would be minimal.

Pregnancy Testing and Confirmation
You indicated that your expected period on February 1 was late, and a home pregnancy test on February 5 showed positive results. This aligns with the typical timeframe for detecting pregnancy, as it usually takes about a week after a missed period for a home test to show accurate results. The ultrasound confirming a gestational sac at 5 weeks and 3 days further supports the pregnancy.

Estimated Conception Date
If conception did occur, it would likely be around the time of ovulation, which means the most probable date would be January 13 to January 19. However, since you had unprotected intercourse after this window, it is unlikely that those encounters led to conception.

Considerations for Future Contraception
If you are considering whether to continue with the pregnancy, it is essential to consult with a healthcare provider to discuss your options. Additionally, if you wish to avoid pregnancy in the future, consider discussing reliable contraceptive methods with your healthcare provider. Options include hormonal contraceptives, intrauterine devices (IUDs), or barrier methods like condoms, which also provide protection against sexually transmitted infections.

Conclusion
In summary, based on your cycle and the timing of your sexual encounters, it is unlikely that the intercourse on January 26 and January 28 resulted in conception. The most probable conception date aligns with your ovulation period. For any further questions or concerns regarding your pregnancy or reproductive health, it is advisable to maintain open communication with your healthcare provider. They can provide personalized advice and support tailored to your situation.

Similar Q&A

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Hello, if the due date is May 14 of this year, the estimated conception date would be around August 21 of the previous year.

Dr. Huang Yiwen reply Obstetrics and Gynecology
Hello, Miss Xiao Xiao: If your menstrual cycle is regular and occurs once a month, then your estimated ovulation date would be around two to three days before or after August 21 of last year.

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The gestational age shown by ultrasound is usually more accurate, so you can count back six weeks from May 7, which may indicate the date of conception.

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Dr. Cao Guotao reply Obstetrics and Gynecology
Hello, based on the information you mentioned, it could possibly be related to the event on January 21st, but this is all speculative, and sometimes there can be a difference of a few days. Wishing you good health.