Pregnancy Dates: When Did Conception Likely Occur?

Pregnancy date

Hello, doctor: My last menstrual period was from March 28 to April 3, with an average cycle of 32 days.
I had sexual intercourse on April 9 (used a condom only when feeling it), on April 11 (used a condom throughout), and on April 17 (ejaculated inside).
The app indicates my next menstrual period is expected from April 29 to May 5.
On April 20, I experienced bleeding and mistook it for my period.
I visited the clinic on April 24 and the pregnancy test showed two lines.
An ultrasound could not detect the embryo.
Is this normal? I would also like to know which date had the highest probability of conception.

Jiajia, 30~39 year old female. Ask Date: 2020/04/28

Dr. Zhang Kunmin reply Obstetrics and Gynecology

Hello, based on your description, it is possible that you are in early pregnancy, likely less than 5 weeks, which is why the ultrasound may not yet show a gestational sac.
There is also a possibility that the gestational sac has not developed or that it is an ectopic pregnancy.
It is recommended that you consult a physician for relevant examinations and evaluations to confirm the implantation location and determine the gestational age before estimating the due date.
Thank you! Wishing you safety and health.
Dr.
Zhang

Reply Date: 2020/04/28

More Info

Based on the information you've provided regarding your menstrual cycle and sexual encounters, let's break down the potential conception dates and address your concerns about the ultrasound findings.

Understanding Your Cycle and Conception Dates
Your last menstrual period (LMP) started on March 28 and lasted until April 3, with an average cycle length of 32 days. This means that your next expected period would be around April 29 to May 4. Given the timing of your sexual encounters:
1. April 9: Sexual activity with partial protection (you felt the condom was on but were unsure).

2. April 11: Sexual activity with full protection (condom used throughout).

3. April 17: Sexual activity with ejaculation inside.

Possible Conception Dates
In a typical menstrual cycle, ovulation usually occurs about 14 days before the next expected period. For a 32-day cycle, ovulation would likely occur around day 18, which would be approximately April 15. Sperm can survive in the female reproductive tract for up to five days, meaning that intercourse on April 17 could potentially lead to conception if ovulation occurred shortly after.

Given this information, the most likely date of conception would be around April 17, as this is closest to your ovulation window. The sexual encounter on April 9, while it may have had a lower chance of resulting in pregnancy due to the partial protection, could still be a factor if ovulation occurred earlier than expected.

Ultrasound Findings
You mentioned that you experienced bleeding on April 20, which you initially thought was your period. However, since you tested positive for pregnancy on April 24, this bleeding could have been implantation bleeding, which can occur when the fertilized egg attaches to the uterine lining. It's not uncommon for women to mistake implantation bleeding for a light period.

Regarding the ultrasound not showing an embryo, this can happen if the ultrasound is performed very early in the pregnancy, typically before 5-6 weeks gestation. At this stage, it may be too early to visualize the gestational sac or embryo clearly. It’s important to follow up with your healthcare provider for repeat ultrasounds to monitor the progress of the pregnancy.

Conclusion
In summary, based on your cycle and the timing of your sexual encounters, the most likely date of conception is April 17. The bleeding you experienced on April 20 could potentially be implantation bleeding rather than a menstrual period. If the ultrasound did not show an embryo, it may simply be too early in the pregnancy for visualization. It is advisable to have follow-up ultrasounds to monitor the development of the pregnancy and confirm viability.

If you have further concerns or if the bleeding continues or worsens, please consult your healthcare provider for personalized advice and care. They can provide you with the most accurate information based on your specific situation and medical history.

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