Abstract MP092: Ultrasound Measures of Abdominal Fat Predict Gestational Insulin Resistance

Abstract

Introduction: Gestational diabetes mellitus (GDM) is a serious condition affecting approximately 10% of pregnancies. Obesity, and particularly abdominal obesity, is strongly associated with insulin resistance, the hallmark characteristic of diabetes. The current standard-of-care is the use of an oral glucose test to diagnose GDM at approximately 25 weeks gestation. After diagnosis, a lifestyle intervention is prescribed. If abdominal fat can be measured during routine prenatal ultrasounds, then it may provide an option for early identification of women at high risk for GDM and, in turn, earlier intervention. Hypothesis: This pilot study tested the hypothesis that deep abdominal fat depots are predictive of gestational insulin sensitivity, regardless of overall body fat. Methods: In 31 nulliparous pregnant women (age 27±4.5, BMI 27±7.8, 71% non-hispanic white), abdominal fat was measured at 18-20 weeks gestation via ultrasound. Two measurements were collected 1 inch above the umbilicus (deep intra-abdominal (IAAT) and subcutaneous (SAT1)); two were immediately below the xyphoid process (pre-peritoneal (PPAT) and subcutaneous (SAT2)). Overall body composition was calculated via 4-compartment model from body density via air displacement plethysmography (BodPod) and body water via bioelectrical impedance (InBody 720) measured at 18-20 weeks gestation, along with post-partum bone density via DXA. Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) was computed using fasting glucose and insulin at 24-28 weeks gestation. Gestational weight gain (GWG) was monitored by medical records. After testing variables for normality, HOMA-IR was log-transformed for partial correlation and multiple regression analyses. Results: HOMA-IR was strongly correlated to overall gestational body fat ( r =.666, p =.003) and measures of regional adiposity ( r =.673 for IAAT, r =.471 for PPAT, r =.627 for SAT1, r =.627 for SAT2, p <.05 for all), but not GWG ( r =.012, p =.957), when controlling for age and race. HOMA-IR remained strongly associated with IAAT and SAT1 ( r = .510 and .490, respectively, p <.05 for both), but not PPAT or SAT2 ( r =.143 and .380, p =.559 and .108, respectively), when correlations were repeated controlling for age, race, and percent body fat. Multiple regression analysis revealed that IAAT and SAT1 were significant independent predictors of HOMA-IR (β= .570 and .491, respectively, p <.05 for both), but not PPAT, SAT2, or overall body fat (β = -.384, .473, and -.164, respectively, p = ns for all). Conclusions: Gestational insulin resistance is strongly associated with intra-abdominal and subcutaneous adipose accumulation in the lower abdomen, independent of overall body fat. Thus, abdominal fat ultrasound measures may be a simple way to identify, early in pregnancy, those who are at high risk for gestational diabetes.