Have you heard of the HAPO study? HAPO is an acronym for Hyperglycemia and Adverse Pregnancy Outcome, a study that attempted to identify poor perinatal outcomes in women whose blood sugar levels did not classify them as gestational diabetic (GDM).
It’s been known for some time that gestational diabetes in women is associated with a higher risk of complications during pregnancy and birth. The effects of milder degrees of hyperglycemia (elevated blood sugars) are not as clearly understood. The HAPO study reported an increasing incidence of the following perinatal complications, correlated with increasing levels of hyperglycemia:
- birth weight greater than the 90th percentile
- cesarean birth
- neonatal hypoglycemia
- cord C-peptide greater than the 90th percentile (C-peptide is produced in higher amounts in response to high levels of blood sugar)
Because of the correlation of even slightly elevated blood sugars with perinatal complications, the HAPO study issued new recommendations for screening of pregnant women:
- At the first prenatal visit, the provider may elect to screen ALL women for GDM, or only high-risk women
- Fasting plasma glucose of 126 or greater is diagnostic of overt diabetes, and the woman should be treated as having pre-existing diabetes
- Fasting plasma glucose of greater than 92 but less than 126 is diagnostic of gestational diabetes
- If the fasting glucose is less than 92, the woman should be tested again at 24-28 weeks with a 75 gram, two-hour oral glucose tolerance test, performed after an overnight fast
- Gestational diabetes will be diagnosed if any results exceed the following: fasting glucose greater than 92, one-hour glucose of 180 or more, and two-hour glucose of 153 or more. To be considered normal, all three levels must be lower than these values.
The HAPO investigators believe that these protocols will significantly increase the number of women who are diagnosed as gestational diabetic. It is estimated as high as 18% of women now considered low risk for gestational diabetes will be diagnosed as diabetic using these standards.
It is known that elevated maternal blood sugar during pregnancy is positively associated with childhood obesity.¹ What we don’t know is the full effect of elevated maternal blood sugar on long-term outcomes for children. The investigators recommend further study to determine these outcomes, along with optimal treatment for women during pregnancy. It remains to be seen whether the American Congress of Obstetricians and Gynecologists will adopt these recommendations or retain the current guidelines.
One physician raises some salient questions about all this new data. Dr. Robert Moses asks, “Could the identification of a greater number of women at risk of an adverse pregnancy outcome itself cause harm? It is well documented that a diagnostic category of GDM, irrespective of the glucose control achieved, in some instances is likely to result in increased interventions, earlier delivery, an increased caesarean section rate, and a higher number of babies being admitted to special care nurseries. Could these real hazards offset some of the potential advantages?” (emphasis mine).
Is this a breakthrough in prenancy care, or just another Pandora’s box about to be opened?
1. Hillier TA, et al. (2007). Childhood obesity and metabolic imprinting. Retrieved online 11/21/10 from: http://care.diabetesjournals.org/content/30/9/2287.full.pdf+html