As placental mammals, humans give birth to live young. Pregnancy begins on the first day of the last menstrual period, roughly two weeks before conception.
A human pregnancy consists of three trimesters and generally lasts around nine months. But how much do you know about how babies develop? For example, did you know some cell types appear only during pregnancy, or that hair usually grows thicker and lusher during pregnancy due to hormones, but that this extra hair falls out months later after giving birth?
