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Had unprotected sex. Done with ultrasound. Concerned about paternity?

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General & Family Physician
Practicing since : 2003
Answered : 1229 Questions
Are 4d ultrasounds a good indication of what a baby will look like at birth? Slept with someone in the early morning of XXXXXXX 19 (condom & plan b 50 hours later & believe I was on birth control, but not positive). Slept with someone else the remainder of XXXXXXX - Feb. Went off birth control Feb 1or2 and bled Feb 5-8. Abdominal ultrasound at 7 weeks indicated EDD 11/18. Ultrasound on 4/26 indicated 11 weeks 3 days CRL 45mm EDD 11/12. Ultrasound 5/14 14weeks 1 day CRL 82mm EDD 11/11. Ultrasounds at 19weeks, 21weeks, 26 weeks all indicate 11/12 due date. Could the XXXXXXX 19 encounter have caused this?

I feel like the 4d ultrasound looks more like the guy from XXXXXXX 19 than the guy in Feb. Why is this?
Posted Wed, 18 Sep 2013 in Pregnancy
Answered by Dr. Vaishalee Punj 2 hours later
Brief Answer:
From dates it seems unlikely

Detailed Answer:

Thanks for posting your query on XXXXXXX

From your dates, it seems that you conceived in the last week of January, most probably around 25th January. Thus it is unlikely that the single sexual encounter on 19th was responsible for the pregnancy.

The kids look very much similar after taking birth as we saw them on ultrasounds. But the baby's face is swollen during pregnancy and after birth. Baby features start to become clear after a few weeks after birth. Thus it is too early to judge the father from the baby's looks at this stage. In fact the looks are very deceiving.

The definitive test to determine paternity is DNA test.

My advice would be to enjoy the pregnancy rather than getting worried about paternity. Take it as it comes.

Let me know if you need further clarification.

Dr Vaishalee
Above answer was peer-reviewed by
Follow-up: Had unprotected sex. Done with ultrasound. Concerned about paternity? 51 minutes later
Wouldn't I have conceived in February with an EDD of 11/12 & since I had bleeding on Feb 5 (withdrawal from discontinuing birth control)? I thought my EDD would have put conception in Feb, thus completely taking the guy from XXXXXXX 19 out of the running. Can you please review the dates?
All of the conception calculators I have done online say that conception took place around Feb 19 (with the EDD 11/12) and Feb 25 (with EDD 11/18). How did you get XXXXXXX 25? Would you advise a paternity test?
Answered by Dr. Vaishalee Punj 8 hours later
Brief Answer:
I calculated with EDD of 11 Nov

Detailed Answer:
Hi again,

Yes you are right. Your date of conception is in February and not in January, which completely offsets the 19th January sexual exposure. If you have been in a monogamous relationship with second partner during the period of conception, then you do not need a paternity test.

I WOULDNOT advise a paternity test.

Even if you are still doubting, I will not advise it, as it has many risks involved in personal life.

Paternity test that is usually done is a DNA test. This test is more than 99% sure.
To rule out the first guy, you will need him to accompany you to the test laboratory for his specimen. The specimen used is a scraping from the inner lining of mouth.
Then you will also need a similar specimen from your baby.
Then the laboratory will test if the DNA matches between the two.
To rule in the second guy you will need him to accompany you.

The cost of this test varies with each laboratory. But is usually around a few hundred dollars.


Dr Vaishalee
Above answer was peer-reviewed by
Follow-up: Had unprotected sex. Done with ultrasound. Concerned about paternity? 14 hours later
Thank you very much. I just get concerned because I feel like she looks more like the XXXXXXX 19 encounter on ultrasounds, but I know the way they look on the inside is not how they always look on the out! So you are confident that the XXXXXXX 19 enounter didn't cause this pregnancy from the US dates/info provided?
Answered by Dr. Vaishalee Punj 14 hours later
Brief Answer:
I am sure

Detailed Answer:
Hi again

From the information that you have provided and from the USG dates, I am very much sure that the 19th XXXXXXX encounter is not responsible for the pregnancy. You can relax and think about other important things about bringing up the baby.

The Last Menstrual Period also happened after the encounter, thus completely ruling out chances of pregnancy from that encounter.

I hope I have clarified your doubt.

Dr Vaishalee
Above answer was peer-reviewed by
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