A 30-year-old female asked:
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when is pregnancy calculated first day of last period or conception because my lmp is 9-8 40 weeks from that would give me a due date of 6/15?

1 doctor answer
Dr. Gerard Honore
28 years experience Fertility Medicine
40 weeks from LMP: 40 complete weeks from the first day of the last normal mentrual period. With uncertain lmp, dating is by ultrasound, but if within 1 week to lmp, then menstrual dating is still used. Obstetrical dating is never based on conception, even with ivf pregnancies.
Answered on Dec 10, 2013

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