human how many days pregnant
The length of a human pregnancy can vary naturally by as much as five weeks. Credit: Â© Jessmine / Fotolia. The length of a human pregnancy can vary naturally by as much as five weeks, according to research published online August 7 in the journal Human Reproduction. Normally, women are given a date for the likely delivery of their baby that is calculated as 280 days after the onset of their last menstrual period.