When Did I Conceive? Pregnancy Timing and Signs

When is sexual intercourse likely to result in pregnancy?

I had my period on June 11th and then again on July 15th, but I haven't had my period since then.
I had sexual intercourse on August 10th and August 16th.
In mid-August, I developed a urinary tract infection and took medication; my doctor mentioned that some medications could delay my period.
However, I still did not get my period in August, so I visited a gynecologist on August 28th for a pregnancy test, which came back negative.
After that, I had sexual intercourse on September 2nd, 3rd, 5th, 12th, 19th, and 20th.
On October 30th, I went to the gynecologist for a pregnancy test, which included a urine test and an ultrasound.
The doctor said I was six weeks pregnant and estimated my due date to be June 19, 2024.
However, I am unsure which day of sexual intercourse led to the pregnancy.
Could it be from the sexual activity in August? Can you help me clarify this, doctor?

Yajun, 20~29 year old female. Ask Date: 2015/11/03

Dr. Lü Lizheng reply Obstetrics and Gynecology

1.
If the due date is June 19, 2005, the estimated conception date should be around September 25.

2.
If a pregnancy test is conducted at the obstetrics and gynecology department on October 30, and the urine test and ultrasound indicate that the gestational age is six weeks, the estimated conception date should be around October 2.

3.
Since the estimated dates do not align with your intercourse dates, there may be discrepancies.

4.
It is recommended to have another ultrasound at a larger hospital for a re-evaluation.
Sincerely, Dr.
Li-Cheng Lu, Taoyuan Hospital.

Reply Date: 2015/11/03

More Info

To determine when conception occurred, it's essential to understand the timing of ovulation, fertilization, and implantation in relation to your menstrual cycle. Based on the information you've provided, let's break down the timeline and clarify some key concepts.

1. Menstrual Cycle Overview: Your last menstrual period (LMP) was on June 11. The average menstrual cycle is about 28 days, but it can vary. You mentioned that your cycles can be longer, averaging around 39 days. This means that ovulation likely occurred later than the typical cycle, possibly around day 24 or so of your cycle, which would be around July 5 or 6.

2. Timing of Ovulation and Conception: Ovulation typically occurs about 14 days before your next expected period. If we consider your LMP of June 11, your next expected period would have been around July 9. If you ovulated around July 5, then any unprotected intercourse around that time could lead to conception. The sperm can survive in the female reproductive tract for up to five days, which means that intercourse on July 8 or 9 could also result in conception.

3. Pregnancy Testing: You mentioned that you had a negative pregnancy test on August 28, which is significant. If you were indeed six weeks pregnant by the time of your October 30 appointment, this would suggest that conception likely occurred around mid to late July. The negative test on August 28 indicates that you were not pregnant at that time, which further narrows down the possible conception window.

4. Impact of Medications: You noted that you experienced a urinary tract infection (UTI) in August and were prescribed medication. While some medications can affect menstrual cycles, they typically do not prevent conception. However, if your cycle was already irregular, the medication could have contributed to the delay in your period.

5. Ultrasound Dating: The ultrasound performed on October 30 indicated that you were approximately six weeks along, which aligns with a conception date around mid to late July. The healthcare provider calculated your due date based on this ultrasound measurement, which is a common practice as it provides a more accurate estimate of gestational age than relying solely on the LMP.

6. Conclusion: Based on the information provided, it is unlikely that the sexual encounters in August resulted in conception, especially since you had a negative pregnancy test at the end of August. The most probable conception date is around early to mid-July, following the unprotected intercourse around that time.
In summary, while it can be challenging to pinpoint the exact date of conception, understanding your menstrual cycle, the timing of ovulation, and the results of pregnancy tests can help clarify when you likely conceived. If you have further concerns or questions about your pregnancy, it's always best to consult with your healthcare provider for personalized advice and information.

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