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Dr. Andrew Rynne

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How to determine the date of conception?

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Dr. Jacqueline Brown

OBGYN

Practicing since :1996

Answered : 1425 Questions

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Posted on Fri, 16 Oct 2015 in Genetics
Question: Hello, I need some help my ex girlfriend is pregnant. She is currently 37 or 38 weeks. We are not sure who the father is. I was with her using the pull out method 22, 23, 24 and 28, of January. The other guy was with her the dates she told me I'm sure there is more. But January 18-19-20-21. According to her he did not pull out or use any other birth control method. However I know pulling out is risky and not the best method I was under the assumption if she got pregnant I would know its mine but oh well. I know my pre ejaculate doesn't contain sperm as I've seen it through microscope 100+ times. And have never had sex more than once in 24 hours. But all it takes is one needless to say DNA test is need as recommended by our obgyn. She said with dates so close and giving sperm has been recorded to live up to a week. There is no telling who the father is with the conception date she said was really only an estimate. She said anywhere from the 21-27 is when she got pregnant but said the 24 or 25 was the most probable according to ultrasound. Her period was January 11th and she took pregnancy test on February 3rd. My question is who is the probable father. Of course no one knows. Until DNA test but is one of us more likely to be the father?
doctor
Answered by Dr. Jacqueline Brown 3 hours later
Brief Answer:
Without a due date you can't know for sure... But-

Detailed Answer:
Hello, and I hope I can help you today.

I reviewed the information you sent and I hope I can provide you some reassurance.

If your girlfriend had the first day of her last period on January 11th she most likely ovulated 14 days later, which is around the 25th. If you were the only one she was with during that time it is most likely to be you. That conception date was confirmed by your OBGYN by an early ultrasound.

However, your OBGYN is correct in telling you that sperm can live up to 10 days inside the reproductive tract.

So from the information you know for sure it is more likely that you are the father, but I agree with your doctor in telling you the only way to know for sure is with DNA.

I wish you the best of luck with this situation and I hope I answered your question adequately. If you need anything further please do not hesitate to contact me.

Best wishes, Dr. Brown
Above answer was peer-reviewed by : Dr. Yogesh D
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Follow up: Dr. Jacqueline Brown 9 minutes later
So even with me pulling out. And him still in her fertile period it is still probably mine? He was with her the 21st that I know of and that's pretty close to when she ovulated and he did not pull out according to her
That's only 4 days away. But if that's still unlikely then it is XXX probably mine
doctor
Answered by Dr. Jacqueline Brown 11 minutes later
Brief Answer:
As I said- that's why you need the paternity test, but...

Detailed Answer:
Hello again,

I know you may have looked at your pre-ejaculate under the microscope, but it is extremely unlikely that you do not secrete some sperm and every ejaculate has millions of sperm. If the sperm dries out while making the slide they will all be killed and not show up on a smear. This is why it is still very possible you could be the father because withdrawal has a 20 percent failure rate.

But it is true, infortunately is not possible to know for sure. I hoped to let you know that it is still a possibility even though you used the withdrawal method. The timing, assuming she ovulated on day 14, which is the 25th, favors you.

So I hope the information I gave you helps ease your uncertainty during this difficult time. I hope your situation works out for the best.

Sincerely, Dr. Brown
Above answer was peer-reviewed by : Dr. Yogesh D
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Follow up: Dr. Jacqueline Brown 9 minutes later
Thank you. I guess we will find out soon enough. I did the microscope in less than 5 minutes I could see bacteria cells and etc but no sperm not even dead ones. But the timing favors me. Looking at ejaculate. I could of course see tons of them. But I could honestly say I did not see just one sperm in pre ejaculate and I even took a vasectomy test and it came back safe or negative safe for unprotected sex which was sensitive to 250000 sperm. But if your saying that there is definitely sperm in pre ejaculate then ill assume its mine unless DNA says otherwise thank you doctor!
doctor
Answered by Dr. Jacqueline Brown 10 minutes later
Brief Answer:
Sir... Did you have a vasectomy? That changes the odds

Detailed Answer:
Well, I was answering you assuming that the slide you prepared was done incorrectly (you need to put the sperm directly into liquid media or it will dry out for sure on a regular microscope slide) but if you had a sperm count done in a lab that says you have no sperm that's different... why did you do that test? Did you have a vasectomy? If you did, and you had a test that says you didn't have sperm in your ejaculate, that's different. If I am misunderstanding you I apologize, I just want to make sure I am giving you the correct information. Please clarify what you mean by a vasectomy test. Thank you, Dr. Brown
Above answer was peer-reviewed by : Dr. Sonia Raina
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Follow up: Dr. Jacqueline Brown 29 minutes later
Yes I have done it on my own microscope and at the lab twice since pregnancy. My own microscope I didn't see any sperm in pre ejaculate. When I went to lab for semen analysis. They said I was normal had good sperm and I asked them to do pre fluid. They did and said there was no sperm in it the two times I did it. They said they was some immature sperm to my understanding cant fertilize an egg. They said that the prefluid would have failed there vasectomy test and basically told me if I pulled out and got no semen in her then there was virtually no chance of me being the father.
They let me watch how its all done the centrifrige and everything. And when I asked if it was normal to have no sperm in prefluid they said yes its actually really not supposed to have any but some guys will have it in it.
doctor
Answered by Dr. Jacqueline Brown 34 minutes later
Brief Answer:
Well the lab doesn't lie but... The accuracy of the test may...

Detailed Answer:
Well I am only familiar with the NIH conclusion that estimates of sperm in pre-ejaculate can be calculated, but being inside a woman is different from lab masturbation. It certainly is difficult to determine exactly when sperm secretion begins while you are beginning to have an orgasm. So they do not recommend, even with a pre-ejaculate analysis, that couples use withdrawal for contraception. There are other studies as well, but no prospective studies that actually look at pregnancy rates after pre-ejaculate analysis. So there is no proof that men who don't have sperm in their pre-ejaculation analysis are actually protected from pregnancy. If you understand scientific studies, you will know that only prospective ones can prove a true statistical connection in vivo. I like the references noted on Wikipedia about pre-ejaculate and you can google the NIH study.

So unfortunately I think we will both have to wait for the lab test to be sure. I hope you are able to cope as best as possible through this difficult time.

Sincerely, Dr. Brown
Above answer was peer-reviewed by : Dr. Prasad
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