Lung maturation in diabetes in pregnancy: if and when to test.

Poorly controlled maternal diabetes in pregnancy may delay fetal pulmonary maturation. However, diabetic women with good glycemic control have fetal lung maturation at the same gestational age as nondiabetic women. With modern ultrasound technology, gestational dates can be accurately assessed in the first or early second trimester. Respiratory distress syndrome is rare in nondiabetic and well-controlled diabetic pregnancies confirmed by early ultrasound to be at or beyond 37 weeks. Early confirmation of dates thus eliminates the need for amniotic fluid assessment of fetal lung maturity prior to elective delivery at or beyond 38 weeks in well-controlled diabetic and nondiabetic women. Poorly controlled diabetic women and pregnancies without early ultrasound verified dates may require amniotic fluid analysis for lung maturity prior to elective delivery.