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Date of last update: 10/14/2017.

Forum Name: Obstetrics

Question: Is there a difference between pregnancy age and baby age?

 natasha22 - Wed Sep 09, 2009 11:11 am

i am pregnant, my last period was july 10, but my conception was around 24 to 26 of july... calculating my pregnancy weeks on sep 6.... i was 8 weeks and 2 days; however when doing the vaginal ultrasound, the baby was only 6 weeks and a half.... i have been told that there is always a difference of two weeks as conception till it happened is 2 weeks... can you please explain for me why there is a difference between pregnancy weeks and baby weeks? and is this normal and healthy for the baby? is there anything i should worry about? is my baby considered as slow in growth?
 Debbie Miller, RN - Wed Oct 14, 2009 11:54 pm

User avatar Hello,
Pregnancy is measured in weeks and days beginning with the last menstrual period, approximately two weeks before conception occurs. This is because conception date actually varies and for convenience for dating a pregnancy, we use the firmer date of period onset rather than the nebulous date of conception. When the doctor says you are 8 weeks along, that means about 6 weeks since the baby was conceived. I know it is confusing, but I think this is the discrepancy you are concerned about. Also, there is always the possibility you ovulated later (or earlier) and that will alter the measurements for dates. Ultrasound dating is considered the most accurate. I'm sure as you go along, the baby will grow as it should so try to relax and enjoy your pregnancy, take care of yourself by eating healthy foods, exercising, resting, avoiding bad habits, using your seat belt and drinking water.

Good luck.

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