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Have unprotected sex. Missing periods. Ultrasound showed 13 weeks at 14 weeks pregnancy. What's wrong?

DOCTOR OF THE MONTH - May 2013
May 2013
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My lmp was October 30. I had sex with one man on november 12/13. It was unprotected but he pulled out several times. I had sex with another man November 20 and he ejaculated inside me. My cycles are always 28-29 days. My last monthly puts my due date at August 5 but when I went for an ultrasound at 14 weeks they said the baby only looked 13 weeks. How likely is it that I ovulated late vs. the ultrasound dating a week off?
Posted Sun, 19 Aug 2012 in Pregnancy
 
 
Answered by Dr. Sree Gouri SR 1 hour later
hi XXXXXXX
Thanks for the query.

the possibilities for ultrasound date disparity are,
-as you had regular periods, there is more chance for occurrence of ovulation around 12th or 13th.
-though withdrawal method was followed, the pre-ejaculate fluid can contain spermatozoa which are sometimes sufficient to cause pregnancy,
-second trimester ultrasound can sometimes show disparity of around 1 week.

the possibilities for late ovulation are,
-sometimes stress and strain, changes in weight, recent illness etc several factors can affect hypothalamo-pituitary-ovarian axis and can delay ovulation, in that case your gestational age according to ultrasound should be correct.

one option is, if at least two ultrasound reports before 24 weeks correlate then you can take that into consideration if not you can go for gestational age according to lmp.


Hope I have answered your query. I will be available to answer your follow up queries. If you are satisfied with all my answer, please rate the answer after closing the discussion.
Take care.
Above answer was peer-reviewed by
 
Follow-up: Have unprotected sex. Missing periods. Ultrasound showed 13 weeks at 14 weeks pregnancy. What's wrong? 25 minutes later
I also forgot to mention the use of the plan b emergency contraceptive pill I took on the twentieth only 2 hours after the occurance. What are the odds of that failing? Is it more probable for the egg to be fertilized and the pill to have effected the time it takes for implantation to occur? The ultrasounds I have gotten after the initial one have varied being a few days further along but they say after the first trimester they are less accurate?
 
 
Answered by Dr. Sree Gouri SR 9 hours later
hi,
if you took emergency contraceptive pill within 2 hours of the act,
the possibilities are,
-it might have given protection against pregnancy,
-as you took pill in the first half of cycle it might have postponed your ovulation also, so with this the chances of fertilization because of intercourse on 20th increases,
-though dating according to first trimester scan will be more accurate, as you are not having that you can take two scan reports before 24 weeks into consideration for approximate estimation, 2 to 3 days variability can be ignored.

-though the emergency pill is having some failure rate that will be low when taken early, as you did.

Wish you Good Health, If you are satisfied with my response please rate the answer after closing the discussion.
Take care.
Above answer was peer-reviewed by
 
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