Factors associated with stillbirth in women with diabetes

Abstract

Aims/hypothesis: Stillbirth risk is increased in pregnancy complicated by diabetes. Fear of stillbirth has major influence on obstetric management, particularly timing of delivery. We analysed population-level data from Scotland to describe timing of stillbirths in women with diabetes and associated risk factors.

Methods: A retrospective cohort of singleton deliveries to mothers with type 1 (n = 3778) and type 2 diabetes (n = 1614) from 1 April 1998 to 30 June 2016 was analysed using linked routine care datasets. Maternal and fetal characteristics, HbA_1c data and delivery timing were compared between stillborn and liveborn groups.

Results: Stillbirth rates were 16.1 (95% CI 12.4, 20.8) and 22.9 (95% CI 16.4, 31.8) per 1000 births in women with type 1 (n = 61) and type 2 diabetes (n = 37), respectively. In women with type 1 diabetes, higher HbA_1c before pregnancy (OR 1.03 [95% CI 1.01, 1.04]; p = 0.0003) and in later pregnancy (OR 1.06 [95% CI 1.04, 1.08]; p < 0.0001) were associated with stillbirth, while in women with type 2 diabetes, higher maternal BMI (OR 1.07 [95% CI 1.01, 1.14]; p = 0.02) and pre-pregnancy HbA_1c (OR 1.02 [95% CI 1.00, 1.04]; p = 0.016) were associated with stillbirth. Risk was highest in infants with birthweights <10th centile (sixfold higher born to women with type 1 diabetes [n = 5 stillbirths, 67 livebirths]; threefold higher for women with type 2 diabetes [n = 4 stillbirths, 78 livebirths]) compared with those in the 10th-90th centile (n = 20 stillbirths, 1685 livebirths). Risk was twofold higher in infants with birthweights >95th centile born to women with type 2 diabetes (n = 15 stillbirths, 402 livebirths). A high proportion of stillborn infants were male among mothers with type 2 diabetes (81.1% vs 50.5% livebirths, p = 0.0002). A third of stillbirths occurred at term, with highest rates in the 38th week (7.0 [95% CI 3.7, 12.9] per 1000 ongoing pregnancies) among mothers with type 1 diabetes and in the 39th week (9.3 [95% CI 2.4, 29.2]) for type 2 diabetes.

Conclusions/interpretation: Maternal blood glucose levels and BMI are important modifiable risk factors for stillbirth in diabetes. Babies at extremes of weight centiles are at most risk. Many stillbirths occur at term and could potentially be prevented by change in routine care and delivery policies.

Keywords: Birthweight; Epidemiology; Neonatal; Pregnancy; Stillbirth; Type 1 diabetes; Type 2 diabetes.

Fig. 1

Mean HbA_1c according to stage of pregnancy and vital status of infant in women with (a) type 1 diabetes and (b) type 2 diabetes. Blue diamond, mean HbA_1c in livebirths; red diamond, mean HbA_1c in stillbirths. Error bars show SD. *p < 0.05, ***p < 0.01 for stillbirth vs livebirth in the same diabetes group at the same pregnancy stage using a generalised mixed model with mother as random effect. Number of available HbA_1c values: pre-pregnancy: 2313 (62%) livebirths and 38 (63%) stillbirths in women with type 1 diabetes; 796 (50%) livebirths and 17 (46%) stillbirths in women with type 2 diabetes; first trimester: 2156 (58%) livebirths and 30 (49%) stillbirths in women with type 1 diabetes; 785 (50%) livebirths and 15 (41%) stillbirths in women with type 2 diabetes; second trimester: 2119 (57%) livebirths and 29 (48%) stillbirths in women with type 1 diabetes; 775 (49%) livebirths and 16 (43%) stillbirths in women with type 2 diabetes; third trimester: 1933 (52%) livebirths and 27 (44%) stillbirths in women with type 1 diabetes; 782 (50%) livebirths and 11 (30%) stillbirths in women with type 2 diabetes

Fig. 2

Stillbirth rate (per 1000 ongoing pregnancies) in women with (a) type 1 diabetes and (b) type 2 diabetes according to gestational age at delivery. Red bars, crude stillbirth rates (per 1000 ongoing pregnancies) on the y-axis; blue line, absolute number of live deliveries on the secondary y-axis