# Association between neck circumference and glucose tolerance levels at 2-6 months postpartum in women with and without gestational diabetes

## TL;DR

Neck circumference during pregnancy is linked to worse glucose metabolism after childbirth in overweight or obese women, regardless of gestational diabetes history.

## Contribution

NC during pregnancy is a novel, simple predictor of postpartum glucose metabolism in women with overweight/obesity.

## Key findings

- Higher NC during pregnancy was associated with elevated HbA1c, fasting insulin, and insulin resistance postpartum.
- NC remained independently associated with fasting glucose and HbA1c after adjusting for BMI and weight gain.
- The association was consistent in women with and without gestational diabetes.

## Abstract

To evaluate the association between neck circumference (NC) measured during pregnancy and markers of glucose metabolism measured 2-6 months postpartum in women with overweight/obesity with and without gestational diabetes (GDM).

This prospective study enrolled 100 pregnant women (including 50 with GDM) with pregestational body mass index (BMI) ≥ 25 kg and < 40 kg/m². The cohort was stratified according to NC tertiles during pregnancy. Glucose metabolism was assessed in the postpartum period. The association between NC during pregnancy and markers of glucose metabolism postpartum was tested using linear regression analysis.

Participants with NC in the third tertile, compared with those with NC in the second and first tertiles, had higher levels of glycated hemoglobin (HbA1c; 5.6 ± 0.4% versus 5.4 ± 0.3% versus 5.3 ± 0.2%, respectively, p = 0.006), fasting insulin (13.2 ± 6.6 µIU/mL versus 11.1 ± 5.8 µIU/mL versus 9.5 ± 4.9 µIU/mL, respectively, p = 0.035), homeostasis model for insulin resistance (HOMA-IR; 3.1 ± 1.7 versus 2.5 ± 1.3 versus 2.1 ± 1.2, respectively, p = 0.035) and triglyceride-glucose index (TyG; 4.6 ± 0.2 versus 4.5 ± 0.2 versus 4.5 ± 0.3, respectively, p = 0.010). In crude linear regression analysis, NC measured during pregnancy was significantly associated with levels of fasting plasma glucose, 2-hour glucose, HbA1c, log HOMA-IR, and TyG index. The association remained after adjustment for age, family history of diabetes, and number of pregnancies. When adjusted for pregestational BMI and gestational weight gain, NC remained independently associated with fasting plasma glucose and HbA1c levels.

The NC measured during pregnancy was positively associated with worse glucose metabolic profile in the postpartum among women with obesity/overweight with and without GDM. The NC measurement may be a feasible tool for early identification of women at a higher risk of developing type 2 diabetes mellitus.