Yesterday, on the first afternoon of Scientific Sessions, I went to a session where the results of the Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) study were presented. The HAPO study was a HUGE study, involving 25,000 pregnant women in countries ranging from the U.S. to Australia to Northern Ireland to Bangladesh. I've done clinical research for 20 years, and have been involved in some "big" studies before, but never more than about 3000 patients in a study done at multiple sites. I can't imagine one 10 times as big!
One reason HAPO was done was partly to see whether the criteria we've used for 40 years to diagnose gestational diabetes (GDM) make sense. It turns out that these criteria were developed to try to find women who have a high risk of developing type 2 diabetes later (gestational diabetes usually disappears with delivery of the baby, but type 2 often appears later). We've known for years that GDM needs to be treated to avoid problems with the newborn baby, such as the baby being very large or getting low blood glucose after delivery.
We thought that women who tested as not having GDM would have little or no risks to their babies. The HAPO study showed that this isn't the case. Slight increases in blood glucose levels during pregnancy, even in the "normal" range, increase the risks of having a large baby (often requiring a cesarean section), a baby who develops low blood glucose, and other problems that we thought only occurred with GDM. The HAPO study also showed that babies born to these mothers with high blood glucose (but not GDM) had high insulin levels at birth. One of the reasons this is important is that we know that the babies of mothers with GDM are ALSO at risk for obesity, insulin resistance, and type 2 diabetes later in life. This finding from HAPO suggests that many more babies may be at risk for type 2 than we thought.
What do the HAPO results mean? I would imagine that we may need to re-think the criteria we use for diagnosing GDM. Maybe more pregnant women need to be treated for high glucose levels, at least with dietary advice. Do we want many, many more pregnant women to be treated with medications, such as insulin, for GDM? It's a complicated issue. In any case, it was very exciting to hear the HAPO results presented, for the first time ever, at Scientific Sessions.