Medical care and pregnancy - Relevance to antepartum care

Normal changes in glucose metabolism in pregnancy Glucose, amino acids, and ketones pass through the placenta to the fetus. Maternal free insulin and glucagon do not traverse the placenta; fetal insulin secretion and glucagon secretion respond to levels of substrate presented to the fetus. Ketones may be associated with adverse effects upon neurophysiological development of the fetus. The “starvation” state is accelerated with pregnancy, and fasting hypoglycemia occurs after 12 hours in the fasting state, with fasting ketosis occurring as well. The “fed” state in pregnancy is characterized by hyperinsulinemia, hyperglycemia, and diminished sensitivity to insulin by multiple tissues (insulin resistance). Insulin resistance is greatest in the third trimester. Multiple hormones in pregnancy, human placental lactogen, prolactin, and progesterone, all contribute to alterations in glucose metabolism and insulin resistance. Risk of diabetes should be assessed in all pregnant women, with women at high risk, receiving glucose challenge testing (50 g of glucola with one hour blood glucose level) as soon as possible in early pregnancy to screen for undiagnosed type II diabetes. Patients who have a prior history of gestational diabetes but are documented with normal glucose testing in early pregnancy may benefit from a prudent diet during pregnancy to avoid excessive weight gain and concentrated fats or simple sugars. These patients should be screened again at 28 weeks as in routine prenatal care. Women with positive screening tests are confirmed or ruled out for the presence of diabetes during pregnancy using a 100 g glucose load and a three-glucose tolerance test.

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