Not really nine months

Gestation length varies greatly

Photo: Teap/iStockphoto; Graph source: A.M. Jukic et al/Human Reproduction 2013

The length of human pregnancy varies naturally by five weeks, researchers have found. A new study followed 125 women from conception to live single births and found the longest pregnancies in women who were older, had previously had long pregnancies or were themselves heavier at birth.

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