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.

Veterinary obstetrics is the same concept for Veterinary medicine.
 

In obstetric practice, an obstetrician or midwife sees a pregnant woman on a regular basis to check the progress of the pregnancy, to verify the absence of ex-novo disease, to monitor the state of preexisting disease and its possible effect on the ongoing pregnancy. A woman's schedule of antenatal appointment varies according to the presence of risk factors, such as diabetes, and local resources.

Some of the clinically and statistically more important risk factors that must be systematically excluded, especially in advancing pregnancy, are pre-eclampsia, abnormal placentation, abnormal fetal presentation and Intrauterine Growth Restriction.

For example, to identify pre-eclampsia, blood-pressure and albuminuria (level of urine protein) are checked at every opportunity.

Placenta praevia must be excluded (PP = low lying placenta that, at least partially, obstructs the birth canal and therefore warrants elective caesarean delivery); this can only be achieved with the use of an ultrasound scan. However, early placenta praevia is not alarming; this is because as the uterus grows along the pregnancy, the placenta may still move away. A placenta praevia is of clinical significance as from the 28th week of gestation. The current management includes a caesarean section. The type of caesarean section is determined by the position (anterior or posterior) of the placenta.

In late pregnancy fetal presentation must be established: cephalic presentation (head first) is the norm but the fetus may present feet-first or buttocks-first (breech), side-on (transverse), or at an angle (oblique presentation).

Intrauterine Growth Restriction is a general designation, where the fetus is smaller than expected when compared to its gestational age (in this case fetal growth parameters show a tendency to drop off from the 50th percentile eventually falling below the 10th percentile, when plotted on a fetal growth chart). Causes can be intrinsic (to the fetus) or extrinsic (maternal or placental problems).