Hypoglycemia. Diabetes tends to be unstable in the first half of pregnancy, and the incidence of hypoglycemia peaks during the irst trimester. Chen and coworkers (2007) identified hypoglycemic events-blood glucose values <40 mg/dL-in 37 of 60 women with type 1 diabetes. A fourth of these were considered severe because the women were unable to treat their own symptoms and required assistance from another person. Caution is recommended when attempting euglycemia in women with recurrent episodes of hypoglycemia.
In a Cochrane database review, Middleton and colleagues (2016) determined that loose glycemic control, defined as fasting glucose valuesr> 120 mg/dL, was associated with greater risks for preeclampsia, cesarean delivery, and birthweight above the 90th percentile compared with women with tight or moderate control. Importantly, no obvious benefit were gained from very tight control, defined by fasting values <90 mg/dL, and there were more cases of hypoglycemia. hus, women with overt diabetes who have glucose values that are viewed by some as "considerably above" this 90 mg/dL threshold can expect good pregnancy outcomes.
Maternal serum alpha-fetoprotein determination at 16 to 20 weeks' gestation is used in association with targeted sonographic examination to detect neural-tube defects and other anomalies (Chap. 14, p. 283). hese levels may be lower in diabetic pregnancies, and interpretation is altered accordingly. Because the incidence of congenital cardiac anomalies is fivefold in mothers with diabetes, fetal echocardiography is an important part of second-trimester sonographic evaluation (Fouda, 2013). Despite advances in ultrasound technology, however, Dashe and associates (2009) cautioned that detection of fetal anomalies in obese diabetic women is more diicult than in similarly sized women without diabetes.
Regarding second-trimester glucose control, euglycemia with self-monitoring continues to be the goal in management. After the first-trimester instability, a stable period ensues. his is followed by a greater insulin requirement due to the elevated peripheral resistance to insulin described in Chapter 4 (p. 56).
During the past several decades, the threat of late-pregnancy stillbirth in women with diabetes has prompted recommendations for various fetal surveillance programs beginning in the third trimester. Such protocols include fetal movement counting, periodic fetal heart rate monitoring, intermittent biophysical profile evaluation, and contraction stress testing (Chap. 17, p. 331). None of these techniques has been subjected to prospective randomized clinical trials, and their primary value seems related to their low false-negative rates. The American
College of Obstetricians and Gynecologists (2016b) suggests initiating such testing at 32 to 34 weeks' gestation.
At Parkland Hospital, women with diabetes are seen in a specialized obstetrical clinic every 2 weeks. During these visits, glycemic control records are evaluated and insulin adjusted. Women are routinely instructed to perform fetal kick counts beginning early in the third trimester. At 34 weeks, admission is ofered to all insulin-treated women. While in the hospital, they continue daily fetal movement counts and undergo fetal heart rate monitoring three times a week. Delivery is planned for 38 weeks.