Retinal microvascular changes in pregnancy linked to postpartum glucose metabolism abnormalities
Changes in retinal microvasculature during pregnancy may signify an increased risk of abnormal glucose metabolism 5 years later, according to a study of the GUSTO* population.
Study participants were 276 pregnant women with singleton pregnancies from the GUSTO study who underwent retinal photography at week 26–28 gestation (baseline) and were assessed for glucose tolerance using a 75 g oral glucose tolerance test at baseline and 5 years postpartum. Of these, 142 women were diagnosed with gestational diabetes mellitus (GDM; fasting glucose ≥7.0 mmol/L and/or 2-hour glucose ≥7.8 mmol/L) at the baseline visit.
Abnormal glucose metabolism was defined as GDM in subsequent pregnancies within the 5-year follow-up period, prediabetes (impaired fasting glucose [fasting plasma glucose (FPG) 6.1–6.9 mmol/L], impaired glucose tolerance [FPG <7.0 mmol/L and 2-hour plasma glucose 7.9–11.0 mmol/L], or HbA1c 5.7–6.4 percent), or diabetes (FPG ≥7.0 mmol/L or 2-hour plasma glucose ≥11.0 mmol/L) diagnosed at 5 years.
About 25 percent of participants who had subsequent pregnancies had GDM (n=26) while 30.4 percent had abnormal glucose metabolism at 5 years postpartum (n=84).
After adjusting for maternal age, education, prepregnancy body mass index, ethnicity, and GDM at baseline, increases in retinal venular calibre at baseline were associated with an increased risk of abnormal glucose metabolism at 5 years postpartum (risk ratio [RR], 1.2, 95 percent confidence interval, 1.0–1.5; p<0.05 for every 10 µm widening in retinal venular calibre). [Diabetologia 2017;doi:10.1007/s00125-017-4441]
Narrowing of retinal arteriolar calibre and retinal venular branching angle were also associated with increased insulin resistance index at 5-year follow-up (HOMA-IR, 1.4 and 1.3 for every 10 µm and 10⁰ decrease, respectively; p<0.05).
The association between retinal microvascular changes during pregnancy and subsequent GDM was not significant.
“[I]t is postulated that abnormalities of the microvasculature signal subclinical pathophysiological changes prior to overt insulin resistance and hyperglycaemia,” said the researchers. “Retinal imaging provides a direct view of the retinal microvasculature that could be a proxy for the systemic microvascular structure,” they said.
“[I]n this cohort of mothers with and without GDM at baseline, altered retinal microvascular morphology … was associated with postpartum insulin resistance represented by fasting insulin level and insulin resistance index,” said the researchers.
“Our findings may … help to provide a potential novel and quantitative predictor … during pregnancy for identifying mothers who are at high risk of abnormal glucose metabolism after pregnancy or in subsequent pregnancies,” they said, recommending that future research assess these outcomes in a larger population and with a longer follow-up period.