1217-P: Insulin Sensitivity and Insulin Secretion Differentially Affect Birthweight and Postpartum Glucose

Background: Insulin deficiency and insulin resistance are two fundamental mechanisms that lead to hyperglycemia. Despite variation in the underlying physiology, individuals with hyperglycemia in pregnancy are treated similarly.

Methods: Pregnant women with diabetes risk factors completed a 2-hr 75-gram oral glucose tolerance test (OGTT) at 10-15 weeks’ gestation, 24-32 weeks’ gestation, and postpartum. We tested for associations between insulin sensitivity (opposite of insulin resistance, Matsuda index) or insulin secretory response (Stumvoll estimate) in the 1st trimester with birthweight percentile (for gestational age and sex) or 2-hr post-OGTT glucose postpartum. We used linear regression, adjusting for age, race/ethnicity, education, gestational age, BMI, GDM treatment (birthweight analyses), weeks postpartum (glucose analyses) and insulin sensitivity (insulin secretory response analyses).

Results: We studied N=151 pregnant women at a median [IQR] =12 [11-13] weeks’ gestation. N=107 had data at median [IQR] 9 [7-13] weeks postpartum. A 1-unit increase in 1st trimester insulin sensitivity (log Matsuda) was associated with a decrease of 6.9 in birthweight percentile (95% CI [-13.7, -0.05] P=0.045). 1st trimester insulin secretory response (log Stumvoll) was not associated with birthweight (β=-12.7 95% CI [-28.3, 2.9] P=0.11). 1^st trimester insulin sensitivity was not associated with postpartum 2-hr OGTT glucose (β=-0.80 95% CI [-9.6, 8.0] mg/dL P=0.86), while a 1 unit increase in 1^st trimester insulin secretory response was associated with a 36 mg/dL decrease in 2-hr OGTT glucose (95% CI [-53.7, -18.8] P=<0.001).

Conclusion: Early pregnancy insulin sensitivity is more strongly associated with birthweight, while insulin secretory response has a stronger relationship with postpartum glycemia. Insulin resistance may confer more risk for perinatal complications, while insulin deficiency may confer more risk for postpartum hyperglycemia.