QuestionQUESTION: Dear Brenda, i am writing to you because i desperatly need to know who the father of my baby would be. I am currently about 21weeks, 3 days pregnant. The first day of my LMP was about the 10th of Nov, 06 and i expected my next period to start on the 12th of Dec, 06 (i have about 33 day long cycles). My period never came on the 12th, and on the 21st Dec i had unprotected sex with another man (me and my bf had broken up) and my period still never came. Three days later on the 24th of Dec i did a home pregnancy test and the result was positive. Up until the 21st of Dec i had slept with no one else but my bf. Two weeks after first sleeping with this other man (on the 3rd of Jan, 07) i had a dating ultrasound and it said the babys gestational age was 6w 4d old with a CRL of 7.5 - 8.0mm and a strong heart beat. My EDD is 25th Aug, 07. Which would mean that the conception date would have been roughly the 2nd of Dec, 06. I had a later scan at 12 weeks and they dated the baby to be 11w 5d with a CRL of 6.1cm. I then had a scan at 19w 5d and they said the measurements were consistent with the above dates. Is there any chance AT ALL that this baby might be the other guys and not my bfs? considering that my period was already 9 days late when i slept with the other guy and that 3 days later i did a HPT and it was positive. The early scan would definatley not be THAT wrong in dating the pregnancy would it? If it was the other guys the baby would have only been 4weeks at the first scan and there is no way that the baby would have a CRL of 7.5mm at that stage is there? Please help me, i really need reassurance, my bf and i are back together and really want this to be his baby:( Do you think it is my bf's baby? Thankyou so much for your help
ANSWER: Dear Tallia,
There is no possible way that you would have gotten a positive pregnancy test 3 days after conception, nor would it be possible that at the first ultrasound on 1/3 there would have been a measurement of 7.5-8.0mm OR a strong heart fetal heart rate if gestational age was only 2 weeks. Fetal heart activity does not become visible until approximately 6 weeks, on occasion mid to late in the 5th week.
Your most likely date of conception was approximately 11/30/06 or within a day or two of that date.
You can stop fretting if the only encounter with anyone other than your boyfriend was on 12/21. That would have been too late. You would have already been pregnant by then.
Hope that this has helped you and answered your question. I wish you well.
Brenda
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QUESTION: Dear Brenda,
Thankyou for your last answer, it was really helpfull. Im sorry to bother you again but i just have a few more questions. Question 1. I was just wondering excactly how accurate dating ultrasounds are in the early stages of pregnancy? When i had my first scan on 3rd Jan 07 (6weeks 4days), how many days at THE MOST could they be off by? How reliable are ultrasounds in determining a babies Gestational age? (im still a bit paranoid about the baby not being my bfs). There is no way that the ultrasounds could be off as much as 19 days is there? Question 2. As my period was due on around the 12th Dec 06, i would have HAD to have concieved before my period was due wouldnt i? otherwise i would have had to have gotten my period? Is that right? because i read that once you ovulate the egg only stays alive for about 24 hours then starts to die, then your period is inevitable in about the next 12 days or so? I know i should stop being paranoid about this but im still worried that the baby might not be my boyfriends. Theres absolutly NO WAY that it could be the other guys baby is there? Thanks so much for putting up with me, none of the doctors i have spoken to have answered my questions!! P.S. would you even see a tiny baby on an ultrasound 2 weeks after conception? If so, what would its CRL be?
ANSWER: Dear Tallia,
The ultrasound at 6 weeks could not have been off by 19 days. Again, fetal heart activity would not have been present at that time. It is just not physiologically possible to have fetal heart activity at 2-3 weeks gestation. And at 2 weeks gestation a CRL could not have been measured. At week 3, the fetus is approximately the size of the head of a pin and approximately .006 inches long.
Ultrasounds which are done in weeks 5-12 are the most accurate as far as dating the pregnancy. Ultrasounds done after the 12th week are less accurate as the pregnancy progresses (for dating purposes).
Yes, you would have conceived before the missed period in December. You won't miss the period unless you have conceived unless you have a history of irregular periods already.
You really can rely on the dating of the ultrasound. It will not be off by that much. Don't stress about the doctors - they are probably reluctant to put themselves out there regarding paternity because the fact is that to know with absolute certainty, you'd have to wait and perform a paternity test after birth. But, this case seems to be fairly clear if they actually looked at the dates and numbers. If you'd like to have some reaffirmation by your doctors, simply ask them if a CRL could have been measured at 2-3 weeks or if fetal heart activity could have been detected at 2-3 weeks. Those are yes/no questions. Hope that will help you.
Brenda
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QUESTION: Dear Brenda,
Thankyou again for your reply :). i was just abit confused by your answer though. When you say that at 2 weeks gestation a CRL could not have been measured, do you mean 2 weeks after conception?. And again when you say that at week 3 the fetus is approximatley .006 inches long do you mean 3 weeks after conception? Because when i had my first ultrasound and they measured the baby 6weeks 4days gestational age, they said that that ment it was concieved 4 weeks 4 days ago. Thankyou!!! Tallia.
AnswerDear Tallia,
Gestational age is always based on the 1st day of the LMP. You've kind of answered your own concerns... on 1/3 they told you that the baby was CONCEIVED approximately 4 weeks, 4 days before. That would have been the end of November, as we figured before.
If it had been conceived on 12/21, the gestational age would have been less than 4 weeks gestational age at your 1/3 ultrasound (that's why I gave you the 3 week measurement).
The references to 2 weeks were in response to you asking, "P.S. would you even see a tiny baby on an ultrasound 2 weeks after conception? If so, what would its CRL be?" So the last answers I gave you were responding specifically to two weeks after conception since that is what you asked about.
Hope that clarifies everything for you! :-)
Brenda
