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Childbirth/conception period


Hello, I am trying to determine when I conceived and ensure which of the two men involved are the father. My lmp was September 9th, however I have not been tracking the length of my cycles and think that I may have irregular periods that differ monthly by a few days to a week but not 100% sure of this. I had intercourse with man #1 on either September 18 or 19. Did not sleep with either for days - until September 25 which is when I had sex with man #2. Man #2 and I had sex regularly after that up until I discovered my pregnancy. On October 18th I was told I was 5-6 weeks pregnant based on HCG levels. I had my first ultrasound on December 19(abdominal ) and it read that I was 13 weeks 5 days pregnant.  Any professional and expert advice would be appreciated!

Unfortunately, you'll need a paternity test to know for certain.  Based on your LMP, you most likely conceived around Sept. 23 but according to your second ultrasound, you most likely conceived around Sept. 28.  Since sperm can live in the reproductive tract for up to 5 days, either man could be the father. Without more accurate measurements or a history of your cycles, there's no way to say for certain without a paternity test.


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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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