Obstetrics (from the Latin obstare, "to stand by") is the surgical specialty dealing with the care of a woman and her offspring during pregnancy, childbirth and the puerperium (the period shortly after birth). Midwifery is the equivalent non-surgical specialty. Most obstetricians are also gynaecologists. See Obstetrics and gynaecology.
The average gestational period for humans is 40 weeks by gestational age and 38 weeks by fertilization age. This is divided into three trimesters.