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How to check for paternity of child during pregnancy?

Mar 2014
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Practicing since : 2001
Answered : 1390 Questions
She says she is pregnant with my children(twins). I had intercourse with her on 4-22-2014. On 7-15-2014 she had an ultra sound and is saying that she is 7-8 weeks pregnant. Timeline of pregnancy seems a little too far off, date of intercourse to ultrasound is almost 12 weeks, not very close to 8 weeks. What is the probability that these offspring are mine? Thank you.
Posted Tue, 5 Aug 2014 in Pregnancy
Answered by Dr. Madhuri N Bagde 29 minutes later
Brief Answer:
detailed answer below.

Detailed Answer:
Hello and welcome,

I understand the question well.

If the ultrasound is showing a gestation of 7-8 weeks on 15th of July then the likely date of the last period is around 20-26th of May. I would be glad if you could provide me with the exact duration of pregnancy in days for example 7 weeks 2 days etc to give an exact date. The ultrasound itself has an inherent error of =/- seven days. So these days may be added or subtracted from the above duration of 20-26 May.

If we assume that the period was on 20 may then the likely date when ovulation occured and pregnancy resulted is 4th of XXXXXXX This may be earlier or later by seven days.

In any case, a contact in April is unlikely to cause this pregnancy. However a more accurate dating ultrasound if available will help clarify matters further but confirmation will need genetic tests. If paternity is an issue better tests like genetic testing of the babies and father will help establish the diagnosis.

Hope this satisfies your query.
Thanks for using HCM.     
Feel free to ask any more questions that you may have.
Dr Madhuri Bagde
Consultant Obstetrician and Gynecologist
Above answer was peer-reviewed by
Follow-up: How to check for paternity of child during pregnancy? 7 hours later
Thank you for your speedy response.
After following up with this female she said that the exact duration was 8 weeks and 6 days, according to the technician, she has a follow up appt with the doctor today to review the ultrasound. The technician also stated that her due date is February 22nd, 2015. Counting back 40 weeks is about May 18, and I left the area April 24th. She also claimed that sperm can live up to 2 weeks inside a women, after a 5 minute Google search I found multiple answers that said 5-7 days XXXXXXX most die within 12-24 hours. What other information do I need to get from her, to make my case that the twins are not mine. I slept with her and will accept the consequences(good or bad), but I need to know the likelihood that they are mine. Can you give me a rough percentage please? If there is a chance that they are mine I will be quitting my job overseas (not based on you answer alone, don't worry) and trying to make things work with her. I appreciate your responses. Thank you.
Answered by Dr. Madhuri N Bagde 7 hours later
Brief Answer:
detailed answer below.

Detailed Answer:
Hello and welcome back,

I understand that the ultrasound says it was 8 weeks and 6 days on 15th July.

According to this she is 62 days pregnant. So if we count back 62 days from 15 July the date of the last period is on 14th May and the babies were most likely conceived 14 days later that is around the 28th of May.
even if we consider an error of 1 week then the babies may have been conceived on 21 May.

If you had sex on 22 April, it is almost a month ago. Even if sperms are alive for 2 weeks [ extremely rare situation almost an exception], then also she has conceived after almost 4 weeks. So these babies are not likely to be yours.

I understand the situation, however you can always go for paternity testing even during pregnancy. So discuss this with the mother. The tests also can be done after delivery of the babies and will establish about you being the father or not. I am glad that you are ready to accept the situation if the babies are yours, but I certainly feel that further testing is needed for confirmation as the dates that you mention do not seem to suggets that you are the likely father.

Hope this clarifies matters.

Tale care and feel free for any further queries.

Dr Madhuri
Above answer was peer-reviewed by
Follow-up: How to check for paternity of child during pregnancy? 32 hours later
One more set of follow up questions. So unfortunately I have played my hand with her, explaining what I feel about the dates not matching up with the pregnancy timeline that she has. She has gotten mad and probably won't give me any more information. But this is what she has said.

She admitted to having another partner 6 weeks after I left, but she was asking me when I left so I am not sure when she thinks I left. Assuming that she has a rough date, that would put her next partner at roughly XXXXXXX 5th, which is fairly close to the dates that you mentioned might be the conception date. Then she states that she knows she had intercourse on the 19th of XXXXXXX I am not sure if this it the "6 weeks later" guy or someone else.

So essentially my question is; is it more likely (provided she is telling the truth about XXXXXXX 19) for conception to take place in the XXXXXXX time frame, or in the April 24th time frame(but showing under development on a ultrasound?) ? Being that I am an engineer I was hoping for maybe some rough percentages? Solid numbers based on an educated guess? Thank you again for your time.
Answered by Dr. Madhuri N Bagde 23 hours later
Brief Answer:
Detailed answer below.

Detailed Answer:
Hello and welcome,

I completely understand your query.

I have already provided you with the dates.

A delayed conception means that the date of conception is not matching with the conception date. But sexual episode is necessary around the date of conception that is in May +/- 1 weeks.

You had left on april and so there is no sex during this date so how can the baby be yours?

An underdeveloped baby does not match with the dates. But this does not happen in early pregnancy. This condition is called fetal growth restriction that is commonly seen after 24-28 weeks. If a baby does not grow in early pregnancy it dies and is termed as a missed abortion. So chances of underdevelopment are not there.

It may or may not be a delayed conception [ if she tells the date of her last menstrual period then we can comment on that]. But even then a sexual episode at the time of conception [ which is in May] is necessary to get pregnant which is missing in your case.

From the information that you had provided the chances of conception in April 24 are almost nil. Unfortunately there are no numbers that I can provide as I do not know her menstrual date and also the ultrasound images are completely unclear [ I would be glad to have a report rather than the images or both if possible]. Even then providing numbers with absolute suerity is not possible but the chance that these are your babies is negligible with the given history.

If she does not know when you left, how does she say that she had a partner 6 weeks later. She may have had the partner earlier as she herself does not know when you left and is just guessing. She may herself be confused, we do not know.

So as of now, I would say that the chacnes that the baby was conceived by sex on 22 April are negligible.

Hope this helps.

I am extremely sorry for the delay but I was busy in a conference. Kindly excuse me. I would also be going tomorrow so there may be a slight delay in response.

Sorry once more.

Dr Madhuri
Above answer was peer-reviewed by
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