Diabetics have triple the normal rate of asymptomatic bacteriuria. Therefore, a urine culture is obtained initially, and appropriate treatment initiated if it is positive. After cessation of therapy, urinary culture is again obtained to confirm elimination of the infection. Protein detected in clean-catch urine specimens should be evaluated by 24-hour urine testing and repeated as needed. In addition to routine prenatal care (see Chapter 10), the development of edema (including carpal tunnel syndrome) is closely monitored. If edema occurs, greater attention to glucose control (eg, returning to daily monitoring) and enhanced bed rest are necessities. There is an increased incidence of preeclampsia in diabetics, which is directly related to glucose control as well as to the presence of preexisting vascular and renal disease.

Assessment of the fetus by glucose memory meters combined with clinical/ultrasound assessment of fetal growth cannot be replaced by other antenatal tests. Fetuses in whom maternal glucose has been well controlled and whose mothers do not smoke or have other organ damage will tolerate pregnancy well.

Patients with poor glucose control, fetal macrosomia, and/or polyhydramnios represent the patients at greatest risk for morbidity and mortality. Biweekly nonstress tests (NSTs) or weekly contraction stress tests are begun at 32 weeks for additional monitoring of poorly controlled patients, patients with complicated vascular disease, or patients who smoke. Weekly NSTs (also from 32 weeks’ gestation) are recommended in patients with insulin-requiring gestational diabetes, with an increase to biweekly recommended after 36 weeks as well as the addition of AFI evaluation. For diet-controlled gestational diabetics, weekly NSTs are usually begun at 36 weeks. All patients should be instructed to make daily assessments of fetal movements and to alert the physician if a decrease is noted. A biophysical profile should be done if decreased movement is noted or if a nonreactive NST occurs.

In the case of abnormal fetal testing, the practitioner should assess gestational age and, if the fetus is found to be mature, should proceed to delivery. If the fetus is intermediate in maturity, amniotic fluid assessment for pulmonary maturity may assist in the decision regarding whether delivery should be effected. Lung maturity should also be assessed before elective induction if glucose control is questionable or if the fetus is less than 38 weeks unless fetal jeopardy is suspected. The lecithin: sphingomyelin ratio should be 2.5 or higher due to the higher incidence of respiratory distress in the fetus. If the fetus is immature, further testing such as contraction stress tests or hospitalization with continuous fetal heart rate monitoring is advised.

Preterm labor is increased in patients with diabetes, and they should be treated with magnesium sulfate as the initial tocolytic agent because the beta mimetics markedly influence glucose control. Corticosteroids increase maternal glucose levels, and therapy should be prescribed to keep levels in the desired range. This therapy may consist of continuous insulin infusion in certain cases.

Induction of labor is recommended at 38 weeks in patients with poor glucose control and macrosomia. Glucose control at a level 100 mg/dL for 24 hours prior to delivery will reduce immediate neonatal hypoglycemia. Prostaglandin gel to ripen the cervix reduces the cesarean section rate, but is not advised without a negative contraction stress test if oligohydramnios is the indication for induction. Insulin-requiring diabetics should be induced at 40 weeks’ gestation if spontaneous labor has not occurred. In any glucose-intolerant patient, the decision to continue pregnancy longer than 40 weeks’ gestation must be carefully considered.