Once the diagnosis of diabetes is established in a pregnant woman, continued testing for glycemic control and diabetic complications is indicated for the remainder of the pregnancy. To some extent, this involves the more intensive use of studies that are part of normal prenatal care (eg, ultrasonography).
During the first trimester of pregnancy, women with diabetes should undergo testing (in addition to normal prenatal laboratory tests) for HbA1C, blood urea nitrogen, serum creatinine, thyroid-stimulating hormone, and free thyroxine levels, as well as spot urine protein-to-creatinine ratio and capillary blood sugar levels 4-7 times daily.
In 1995, Moses et al assessed the prevalence of gestational diabetes mellitus in patients with various risk factors and recommended universal testing.Gestational diabetes mellitus was diagnosed in 6.7% of the women overall, in 8.5% of the women aged 30 years or older, in 12.3% of the women with a preconception body mass index of 30 kg/m2 or greater, and in 11.6% of women with a family history of diabetes in a first-degree relative. A combination of one or all of these risk factors predicted gestational diabetes mellitus in 61% of cases. Gestational diabetes mellitus was present in 4.8% of the women without risk factors.
In all women with preexisting diabetes mellitus, there is a 9-14% rate of miscarriage. Current data suggest a strong association between the degree of glycemic control before pregnancy and the miscarriage rate. Suboptimal glycemic control has been shown to double the miscarriage rate in women with diabetes. A correlation also exists between more advanced diabetes and miscarriage rates. Patients with long-standing (>10 y) and poorly controlled diabetes (glycohemoglobin exceeding 11%) have been shown to have a miscarriage rate of up to 44%. Conversely, excellent glycemic control normalizes the miscarriage rate.
In diabetic pregnancy, perinatal mortality has decreased 30-fold since the discovery of insulin in 1922 and the introduction of intensive obstetrical and infant care in the 1970s. Nevertheless, the current perinatal mortality rates among women who are diabetic remain approximately twice those observed in the nondiabetic population.
Diabetic retinopathy is the leading cause of blindness in women aged 24-64 years. Some form of retinopathy is present in virtually 100% of women who have had type 1 diabetes for 25 years or more; of these women, approximately 1 in 5 is legally blind. A prospective study showed that although half the patients with preexisting retinopathy experienced deterioration during pregnancy, all the patients had partial regression following delivery and returned to their prepregnant state by 6 months postpartum.