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Had intercourse with two partner. Possibility of pregnancy?

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General & Family Physician
Practicing since : 2005
Answered : 2565 Questions
I slept with two people 1 month apart. First encounter was early morning XXXXXXX 19 (2am) , other encounter was the remainder of XXXXXXX - Feb. EDD by abdominal ultrasound at 7 weeks was 11/18. Ultrasounds at 11, 14, 19, 21, 26 weeks gave EDD 11/21. Possible I conceived from the XXXXXXX 19 encounter?
Posted Fri, 20 Sep 2013 in Pregnancy
Answered by Dr. Prasad 3 hours later
Brief Answer:
When was your last menstrual period?

Detailed Answer:

Predicting the date when you conceived is often confusion when two encounter fall within a short period of time. In your case the expected date falls on November 18th; so in my opinion you conceived from February encounter and not January. If your last period was after the January 19th encounter, then I would doubly rule out January 19th encounter as the cause of pregnancy here.

Write back for further information.

Above answer was peer-reviewed by
Follow-up: Had intercourse with two partner. Possibility of pregnancy? 10 hours later
There's a month between encounters, therefore wouldn't that be enough to determine with certainty? I used a condom & plan b 50ish hours later with XXXXXXX 19 encounter. I was also on birth control, but often miss a pill. I went off birth control for good in the middle of the pack on feb 2. I had withdrawal bleeding on feb 5-8. Would this count as a period? What are your thoughts on XXXXXXX 19 encounter with new info?
Answered by Dr. Prasad 1 hour later
Brief Answer: XXXXXXX 19th encounter seems to be safe one...

Detailed Answer:

In my opinion, January 19th seems to be a safe and protected one. The reasons being:
1. Though plan b is more effective when taken within 24 hours, at 50 hours it is more than 80% effective in protecting against pregnancy.
2. The 3 days withdrawal bleeding between February 5 and 8 is sufficient to exclude pregnancy.
3. Finally expected date of conception is calculated by Negli's formula. This uses last menstrual period date to calculate EDD. Accordingly EDD calculated considering February as last menstrual period falls in the month of November. This correlates with EDD calculated on scans.

There January 19th encounters is a safe one. You conceived after the last withdrawal bleeding days ; that's the February encounters.

I hope this information is convincing. Let me know if you need clarifications.


Above answer was peer-reviewed by
Follow-up: Had intercourse with two partner. Possibility of pregnancy? 20 minutes later
Thank you. Wouldn't ultrasounds also show that the XXXXXXX 19 encounter was impossible? I have read that first trimester ultrasounds are more accurate then LMP dating and all of my ultrasounds have lined up with 11/12 due date. Wouldn't it be impossible for all ultrasounds to be off by a month?
Answered by Dr. Prasad 1 hour later
Brief Answer:
1st trimester scan dates are accurate...

Detailed Answer:

EDD date is calculated indirectly on ultrasound. The dates are calculated based on the growth of the baby. There for calculated ddates can be off the real dates only if the baby's growth is abnormal. To be more precise, the calculated date would be off by a month if you have the growth of the fetus is restricted.

That being said, if the sonologist feel growth doesn't match the duration of pregnancy, then EDD is calculated as per negli's formula using period days.

Therefore first trimester dates are very rarely inaccurate.

Further, ultrasound provides no information about the date of conception. It is calculated retrospectively as I did using EDD and last period date.

Based on the details given I am more than convinced that you conceived only after February 5th. January 19th encounter was a safe one.

Write back if you need clarification. If you have no more questions please close this discussion and review.

Thank you and best wishes...
Above answer was peer-reviewed by
Follow-up: Had intercourse with two partner. Possibility of pregnancy? 2 days later
When would you discover that growth is restricted? I've heard that all fetuses grow at the same rate in the first trimester. Would you be able to detect fetal growth restrictions in the first trimester, thus making dates a month off? All of my ultrasounds have lined up perfectly, so therefore wouldn't that disclude fetal growth issues? Sorry I am just confused.
Answered by Dr. Prasad 7 hours later
Brief Answer:
Restriction is noticed in the late trimester...

Detailed Answer:

I apologize if my previous replies are confusing to you. I shall try to clarify your confusion today.

1. Ultrasound findings are time dependent. In the sense the values and findings documented depends on the period of pregnancy. What is normal finding during first trimester is not normal during late trimester.

2. As far as Expected date of delivery (EDD) is concerned, it is calculated based on various fetal growth parameters noted during the scan. The larger the baby is, pregnancy is more close to term delivery and EDD AND vice-versa.

3. In your case, EDD is in the month of November. This implies in all normal cases conception is in the month of February.

4. If you conceived in January, you would be in the term stage in the month of October. That means, Ultrasound scan EDD record in off by a month. This is a possibility only if the growth parameters are smaller than what it needs to be. In medical science, we call such a condition as small for gestational age baby or intrauterine growth retarded babies.

5. Both this condition are appreciated only in the late trimester - late second and third trimester. It is not well noticed in the early trimester. This precisely is the reason why I said, first trimester EDD reports are usually very accurate.

6. Since first trimester EDD falls in the month of November; it is unlikely that you conceived in the month of January. Moreover as you used plan B after January 19th encounter followed by withdrawal bleeding later on, it makes pregnancy highly unlikely. In all probabilities February encounters after the 5th day were responsible for your pregnancy.

Hope it is clear now. Write back for enquiries.

Above answer was peer-reviewed by
Follow-up: Had intercourse with two partner. Possibility of pregnancy? 17 minutes later
Thank you that makes sense.

Since my ultrasounds have lined up perfectly - last ultrasound was at 27 wks & gave EDD of 11/12 I can conclude that growth restriction mostly likely isn't an issue & dating is accurate, not a month off?

Also I just read in my first question I stated that the EDD was 11/21, but I flipped the numbers. The actual due date is 11/12. Does this change anything?
Answered by Dr. Prasad 53 minutes later
Brief Answer:
That doesn't change my opinion...

Detailed Answer:

Well, EDD documented on ultrasound scan is always plus/minus 2 weeks. Besides that my opinion about the date of conception is not entirely based on ultrasound EDD dates. Therefore I stick to my opinion.

And yes, sequential ultrasound reports seems to be perfect as far as EDD dates, suggesting everything was in order. So February conception it is....

Hope this helped.

Good luck!!
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