Delivery of the baby through an incision in the abdominal and uterine walls when delivery through the birth canal is impossible or dangerous. This procedure was performed as early as 715 BC and can be lifesaving for both the infant and the mother in certain situations. However, elective cesarean sections (those scheduled in advance and performed before a woman goes into labor) when performed before term are a significant cause of medical problems in the baby. If a cesarean section is performed before the infant's lungs have completely matured, the infant may have serious respiratory problems. Elective cesarean sections should be performed only if there is good evidence that fetus has mature lungs. Recommendations of the American College of Obstetricians and Gynecologists (1995) for minimizing the risk of lung immaturity are presented below. They apply only to women who have had normal menstrual cycles and who had not been using oral contraceptives immediately before conception. Other women should be evaluated using other methods to make sure that the fetus' lungs are mature. The criteria are as follows:
1. Fetal heart tones should have been documented for 20 weeks by nonelectronic fetoscope or for 30 weeks by Doppler.
2. It has been 36 weeks since a positive serum or urine chorionic gonadotropin pregnancy test was performed by a reliable laboratory.
3. An ultrasound measurement of the crown-rump length, obtained at 6-11 weeks, supports a gestational age of at least 39 weeks.
4. An ultrasound, obtained at 12-20 weeks confirms the gestational age of at least 39 weeks determined by clinical history and physical examination.
An alternative method to assure fetal lung maturity is to perform an amniocentesis and measure chemicals in the amniotic fluid. The concentrations of these chemicals are a good reflection of lung maturity status.