Nurses Health Study, hyperglycemia and adverse pregnancy outcome follow-up data
The new findings from the nuMoM2b–HHS study add to a robust and growing body of evidence that pregnancy is an important window to future health, and that follow up and screening after GDM and HDP are crucial.
Regarding GDM specifically, “there’s quite a bit of literature by now demonstrating that GDM history is a risk factor for hypertension, even 1-2 years post partum, and that the risk is elevated as well for dyslipidemia and vascular dysfunction,” Deirdre K. Tobias, D.Sc., an epidemiologist at Brigham and Women’s Hospital and assistant professor of nutrition at Harvard TH Chan School of Public Health, Boston, said at the DPSG meeting.
An analysis of the Nurses Health Study II (NHS II) cohort published in 2017 found a 40% higher relative risk of cardiovascular disease events (largely myocardial infarction) in women who had GDM, compared with women who did not have GDM over a median follow-up of 26 years. This was after adjustments were made for age, time since pregnancy, menopausal status, family history of MI or stroke, hypertension in pregnancy, white race/ethnicity, prepregnancy BMI, and other factors (JAMA Intern Med. 2017;177[12]:1735-42).
The NHS data also have shown, however, that the elevated risk for cardiovascular disease after a GDM pregnancy “can be mitigated by adopting a healthy lifestyle,” said Dr. Tobias, lead author of the 2017 NHS II analysis. Adjustments for postpregnancy weight gain and lifestyle factors attenuated the relative risk of cardiovascular disease events after a GDM pregnancy to a 30% increased risk.
Dr. Tobias and colleagues currently are looking within the NHS cohort for “metabolomic signatures” or signals – various amino acid and lipid metabolites – to identify the progression of GDM to type 2 diabetes. Metabolomics “may help further refine our understanding of the long-term links between GDM and prevention of type 2 diabetes and of cardiovascular disease in mothers,” she said.
The Hyperglycemia and Adverse Pregnancy Outcome (HAPO) Follow-Up Study, in the meantime, is documenting associations of maternal glucose levels during pregnancy not only with prediabetes or type 2 diabetes 10-14 years later, but also with measures of cardiovascular risk in mothers 10-14 years later.
Just as perinatal outcomes were strongly associated with glucose as a continuous variable in the original HAPO study, “it’s clear there’s a progressive increase in the risk of [later] disorders of glucose metabolism as [fasting blood glucose levels and 1- and-2-hour glucose values] in pregnancy are higher,” said Boyd E. Metzger, MD, the Tom D. Spies emeritus professor of metabolism and nutrition at Northwestern University, Chicago, and principal investigator of the original HAPO study and its follow up.
Dr. Boyd E. Metzger
“Another message is that the more normal you are in pregnancy, the more normal you will be many years later. Good values [during pregnancy] produce good outcomes.”
Currently unpublished data from the HAPO Follow-Up Study are being analyzed, but it appears thus far that GDM is not associated with hypertension (per the old diagnostic threshold) in this cohort after adjustment for maternal age, BMI, smoking, and family history of hypertension. GDM appears to be a significant risk factor for dyslipidemia, however. HDL cholesterol at follow-up was significantly lower for mothers who had GDM compared with those without, whereas LDL cholesterol and triglycerides at follow-up were significantly higher for mothers with GDM, Dr. Metzger said.