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Childbirth/Please help me! I need to know conception date from ultrasound results!


QUESTION: Hello. I am currently pregnant, and I really need help, because I am in this horrible situation. I know it's my fault, but it would be wonderful if you could please take some time to help me :(

I had sexual intercourse with 2 different men:
-Man #1: 12/19/2012
-Man #2: 12/29/2012 or 12/30 (don't remember which day)

I had three early ultrasounds
-#1 on 2/8/2013: Gave me gest. age of 7w6d, with due date 9/21/13
-#2 on 2/14/2013: Gave me gest. age of 8w 6d, with CRL of 23mm
-#3 on 2/14/2013 (at another clinic): Gave me gest. age of 9w 2d

My LMP, which is not every regular, was 12/14/2012 or 12/15/2012.

Please help me determine which of those men is my baby's father!

Thank you so much for your time.


ANSWER: Man #2 is the father.  It lines up perfectly as your likely conception date was 12/29 based on your measurements and ultrasound results.

---------- FOLLOW-UP ----------

QUESTION: Hi Catherine, first of all, thank you very much for your answer :)

I just had another question. At my 20-week ultrasound (anatomy scan), I found out that I am having a boy. I have seen a lot of stuff on the internet saying that Y sperms have a shorter lifespan than X sperms. So if you're having a boy, intercourse happened close to ovulation?

I don't know how much of that is true, but what is your opinion on this?

Thank you!

There is an entire gender selection method devoted to the theory that male sperm are faster but less hardy and female sperm are bigger, slower but live longer so that if you want a boy, you should have intercourse on the day of ovulation and if you want a girl, you should have intercourse on the two days prior to ovulation.

It is called the Shettles Method and does have some validity but has not been definitively supported.


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Catherine Beier MS CBE


I can provide evidence-based information and current research findings concerning childbirth and pregnancy. My specializations include natural childbirth, pregnancy and birth interventions, fetal positioning, labor induction, choosing a care provider, midwives, homebirth, unassisted birth, natural pain relief, medications in pregnancy and birth, informed consent, understanding the risks and benefits of childbirth choices, doulas, waterbirth, childbirth methods, childbirth education classes, cesarean section, and VBAC.


I have been a childbirth educator, mother, author, public speaker, researcher, and birth advocate for the past 9 years. I am also the author of, a site dedicated to natural childbirth and pregnancy information. I publish evidence-based articles on pregnancy, childbirth, newborn care, and post-partum care. I'm also a mother of three children, two daughters and one son all born naturally.

My book, Birth Outside the Box, was published in 2007.

I hold a Master's degree in communication disorders with an emphasis in child development. I am also an independent childbirth educator.

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