When the test was administered to high-risk patients at Los Angeles County Women’s Hospital, including women with diabetes, a negative result predicted that a baby would not die within the next week. The contraction stress test was a major breakthrough. It was the first biophysical test for fetal compromise and was important for pregnancies complicated by diabetes. However, it had to be done on the labor and delivery floor, it could take hours, and it might not be definitive if one couldn’t produce enough contractions.
In the mid-1970s, the nonstress test, which relied on the presence of fetal heart rate accelerations in response to fetal movement, was found to be as reliable as the contraction stress test. It became another important tool for prolonging gestation in women with type 1 diabetes.
Even more predictive and reliable was the biophysical profile described several years later. It combined the nonstress test with an assessment using real-time fetal ultrasound of fetal movements, fetal tone and breathing movements, and amniotic fluid.
So, in a relatively short period of time, antepartum surveillance progressed from the contraction stress test to the nonstress test to the biophysical profile. These advances, along with advances in neonatal intensive care, all contributed to the continued decline in perinatal mortality.
Dr. Landon: You have taught for many years that the principal benefit of these tests of fetal surveillance is not necessarily the results identifying a fetus at risk, but the reassuring normal results that allow further maturation of the fetus that is not at risk in the pregnancy complicated by type 1 diabetes.
You also taught – as I experienced some 40 years ago when training with you at the University of Pennsylvania – that hospitalization later in pregnancy allowed for valuable optimization of our patients’ insulin regimens prior to their scheduled deliveries. This optimization helped to reduce complications such as neonatal hypoglycemia.
The introduction of the first reflectance meters to the antepartum unit eliminated the need for so many blood draws. Subsequently, came portable self-monitoring blood glucose units, which I’d argue were the second greatest achievement after the introduction of insulin because they eliminated the need for routine antepartum admissions. What are your thoughts?
Dr. Gabbe: The reflectance meters as first developed were in-hospital devices. They needed frequent calibration, and readings took several minutes. Once introduced, however, there was rapid advancement in their accuracy, size, and speed of providing results.
Other important advances were the development of rapid-acting insulins and new basal insulins and, in the late 1980s and early 1990s, the development of insulin pumps. At Penn, we studied an early pump that we called the “blue brick” because of its size. Today, of course, smaller and safer pumps paired with continuous glucose monitors are making an enormous difference for our patients with type 1 diabetes, providing them with much better outcomes.
Dr. Landon: A century after the discovery of insulin, congenital malformations remain a problem. We have seen a reduction overall, but recent data here and in Sweden show that the rate of malformations in pregnancy complicated by diabetes still is several-fold greater than in the general population.
The data also support what we’ve known for decades – that the level of glucose control during the periconceptual period is directly correlated with the risk of malformations. Can you speak to our efforts, which have been somewhat, but not completely, successful?
Dr. Gabbe: This is one of our remaining challenges. Malformations are now the leading cause of perinatal mortality in pregnancies involving type 1 and type 2 diabetes. We’ve seen these tragic outcomes over the years. While there were always questions about what caused malformations, our concerns focused on hyperglycemia early in pregnancy as a risk factor.
Knowing now that it is an abnormal intrauterine milieu during the period of organogenesis that leads to the malformations, we have improved by having patients come to us before pregnancy. Studies have shown that we can reduce malformations to a level comparable to the general population, or perhaps a bit higher, through intensive control as a result of prepregnancy care.
The challenge is that many obstetric patients don’t have a planned pregnancy. Our efforts to improve glucose control don’t always go the way we’d like them to. Still, considering where we’ve come from since the introduction of insulin to the modern management of diabetes in pregnancy, our progress has been truly remarkable.