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Is it possible to have a false negative on a pregnancy test…

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Is it possible to have...
Is it possible to have a false negative on a pregnancy test 30,32,36, and 37 days after sex?
Submitted: 1 year ago.Category: OB GYN
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Answered in 27 minutes by:
8/3/2017
OB GYN Doctor: Dr Uzair, Doctor replied 1 year ago
Dr Uzair
Dr Uzair, Doctor
Category: OB GYN
Satisfied Customers: 10,516
Experience: MBBS, years of experience in the field of Surgery and Emergency Medicine.
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Hello, my name is***** and I shall be assisting you today. I'm reviewing your query & will get back to you shortly. Thank you for your patience.

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OB GYN Doctor: Dr Uzair, Doctor replied 1 year ago

No, it is least likely. Almost zero chance.

Hope this helps.
Please do not forget to leave a positive rating for the service by clicking on the stars on top of the screen.

Have a good one.

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Customer reply replied 1 year ago
Ok so even if you have early pregnancy symptoms but have negative tests then that means there is no chance for pregnancy?
OB GYN Doctor: Dr Uzair, Doctor replied 1 year ago

Yes, that is right.

Hope this helps.
Please do not forget to leave a positive rating for the service by clicking on the stars on top of the screen.

Have a good one.

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Customer reply replied 1 year ago
This is why I am confused. Saw these on some forums online. Don't understand how it is possible
Customer reply replied 1 year ago
Look at dana_84
OB GYN Doctor: Dr. J, Board Certified OB/GYN replied 1 year ago
Dr. J
Dr. J, Board Certified OB/GYN
Category: OB GYN
Satisfied Customers: 815
Experience: Gynecologist
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Hi there. Board-certified obgyn here. First, it's really hard to trust what people are saying in an online forum, because we don't have access to the actual medical facts. I have taken care of thousands of pregnant women and despite hearing many stories such as what's being shared on the online forums, I have never, ever personally seen it. Now that being said, I never say never, so probably in the history of the world a strange phenomenon like this has occurred, though probably far less often than people talk about it.

Secondly, let's discuss when a pregnancy test would turn positive. In order for a pregnancy to occur, a sperm must meet an egg. If a woman is having a period about once a month, that means she "ovulates" (releases an egg) about once a month. That egg is "viable", meaning able to survive and be fertilized (ie, get pregnant) for about 48 hours. Sperm, on the other hand, can survive for, at the very longest, 7 days inside a woman's reproductive tract. We also know that most pregnancies will have a positive urine pregnancy test (the test where you pee on a stick) within 14 days after fertilization, right around the time when you would be expecting a period, if you were someone who has a monthly period.

So, in theory, one could have intercourse and have sperm released into the reproductive tract, then ovulate 7 days later, and get pregnant despite having had sex a full 7 days prior. Adding in the 14 days it takes for a pregnancy test to turn positive, this totals 21 days after sex, at the very latest, that you would be testing positive for pregnancy.

All that being said, if your period is late and you are very worried about pregnancy ...bloodwork does not lie. Urine pregnancy tests expire, can be mishandled, or the test may not be run appropriately, but bloodwork is a very accurate way to test for pregnancy. So if you are worried about pregnancy, your period is late, and your pregnancy tests are all negative, some bloodwork may ease your mind. Hope this answer helps!

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Customer reply replied 1 year ago
Thank you for going so in depth. I guess I will go ahead and tell you the full story so you can have a better understanding of my situation. So my girlfriend and I had an accident on June 27 and she took plan b immediately afterwards. She got her period 3 days later and it lasted for 7 days, with 2 of those days being just spotting. For the past 6 days she has been feeling really bad. Having some early pregnancy symptoms, the most prominent one is the nausea. She has taken 6 pregnancy tests. One at a doctors office Tuesday morning, which was 37 days after sex. Today is day 35 of her cycle and she still hasn't got her period. Last month she had a 35 day cycle. With that being said, she is also irregular and she has been stressing this month and also has not been eating hardly anything the past week or two
OB GYN Doctor: Dr. J, Board Certified OB/GYN replied 1 year ago

Ah I see. Ok. Does she know when her period started in June? What I'm trying to get at is where she was in her cycle when the accident occurred.

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Customer reply replied 1 year ago
She was on day 32 of her cycle when it happened
Customer reply replied 1 year ago
I know that means that she shouldn't have been fertile but it's hard to know since she is irregular
OB GYN Doctor: Dr. J, Board Certified OB/GYN replied 1 year ago

What you're telling me is very reassuring. I think you guys are in the clear. I understand that she has irregular cycles so it's impossible to know when she ovulated in June, but we know that Plan B prevents 7 out of 8 pregnancies. The way that Plan B works is by delaying ovulation. The idea is, sperm can hang out for up to a week. So after an act of unprotected intercourse, you want to delay ovulation far enough out that any sperm in there will lose viability before you actually ovulate. If Plan B is not effective at preventing a pregnancy, it's usually because the woman ovulated in the 1-2 days prior to intercourse. So, it can't delay ovulation if ovulation has literally just occurred.

Just statistically speaking, a lot of very unlikely things would ALL have to have happened in order for there to be a pregnancy - your girlfriend would have to have ovulated VERY late in the cycle (a Day 30 ovulation. Usually ovulation occurs Day 12-16ish, and in someone with a 35 day cycle, ovulation would be around Day 21), AND Plan B would have to fail, AND all those pregnancy tests would have to be falsely negative. I believe in data, and the data is telling me you're in the clear. May I also add that taking Plan B will worsen irregular periods. The fact that she had a bleed after taking Plan B is very reassuring that the Plan B did its job - a big dose of progesterone which (in addition to delaying ovulation) causes the uterine lining to shed and bleed. I'm not surprised that her period isn't on time this month, because Plan B can throw things out of wack. I think you guys are OK. Hang in there!

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Customer reply replied 1 year ago
Ok thank you for always being so in depth. That is what I was thinking but with the early pregnancy symptoms and no period yet I can't help but be worried.
OB GYN Doctor: Dr. J, Board Certified OB/GYN replied 1 year ago

Again, having her doc order bloodwork (a quantitative hcg level) might do a lot to put you at ease. But also, many symptoms of the luteal phase (the phase in the cycle after ovulation, before a period actually starts) reflect the high level of progesterone at that time - nausea, bloating, increased appetite, mood changes etc. Progesterone is also the predominant hormone of pregnancy, so we see many of those symptoms in pregnancy as well.

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Customer reply replied 1 year ago
Ok I thought about seeing if she would get blood work but she thinks that is stupid since she had a period and she has taken 6 tests
Customer reply replied 1 year ago
Would you recommend that I tell her to get a quantitative hcg blood test done? Still no period. And she feels nauseous after she eats. She still hasn't been eating much. Her doctor prescribed her some stomach medicine about 5 days ago and she takes that after she eats something and that helps.
Customer reply replied 1 year ago
Please respond. You have been so helpful
OB GYN Doctor: Dr. J, Board Certified OB/GYN replied 1 year ago

Hi there. My apologies, I was away from my computer over the weekend.

In response to your question, I think a blood serum quantitative HCG measurement is not a bad idea even with a negative urine pregnancy test. The most likely scenario is that this is her irregular periods just being irregular and unpredictable, but bloodwork will do a lot to put you both at ease.

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Customer reply replied 1 year ago
Thank you for responding. I told her about doing a blood test and she said no because she doesn't think she should spend money on that since she has Gotten negative tests. I wish she would get a blood test. I mean I do kind of agree with her though with the fact that I don't understand how it is possible to get 6 false negative tests that claim to be 99.9% accurate
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