Fetal and pregnancy dates are not the same—when a woman is 24 weeks pregnant, her growing baby (fetus) is about 22 weeks old. This is because the start of the pregnancy is counted from the first day of her last menstrual period (LMP), but the embryo doesn't start growing until about 2 weeks later.
Last Revised: November 10, 2010
Author: Healthwise Staff
Medical Review: Sarah Marshall, MD - Family Medicine & Kirtly Jones, MD - Obstetrics and Gynecology
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