Biology (11th Edition)

Published by McGraw-Hill Education
ISBN 10: 1-25918-813-2
ISBN 13: 978-1-25918-813-8

Chapter 53 - Animal Development - Review Questions - Synthesize: 3

Answer

Women don't menstruate when pregnant because they don't ovulate, which precedes menstruation.

Work Step by Step

This is due to high levels of female sex hormones made during pregnancy, though, especially in the early months of a pregnancy, some women do have breakthrough bleeding at the time for a menstrual period, though much less than during a normal period. A few may even ovulate during the first month after conceiving--it's rare but known for a woman to carry two babies conceived a month apart.
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