Maternal blood glucose levels and body mass index are the most important modifiable risk factors for stillbirth in women with pre-pregnancy diabetes, according to study results published in Diabetologia.

In this retrospective cohort study investigating maternal and fetal characteristics associated with elevated risk for stillbirth in diabetes, researchers followed 3778 babies born to mothers with type 1 diabetes (T1D) and 1614 babies born to mothers with type 2 diabetes (T2D). All were singleton births that occurred between April 1998 and June 2016. They compared maternal and fetal characteristics as well as glycated hemoglobin (HbA1c) data and timing of delivery between participants who had stillbirths and live births.

There were 16.1 stillbirths per 1000 deliveries (n=61) among mothers with T1D and 22.9 per 1000 deliveries (n=37) among mothers with T2D. Factors associated with stillbirth in mothers with T1D were higher HbA1c level before pregnancy (odds ratio [OR], 1.03; P =.0003) and later in pregnancy (OR, 1.06; P <.0001). For mothers with T2D, factors associated with stillbirth were higher maternal body mass index (OR, 1.07; P =.02) and higher HbA1c level before pregnancy (OR, 1.02; P =.016).

Compared with infants in the 10th to 90th percentile for weight at birth, infants born small for gestational age (<10th percentile) were at significantly greater risk for stillbirth. Stillbirth rates were 6 and 3 times higher for small for gestational age infants born to mothers with T1D (n=5 stillbirths; n=67 live births) and T2D (n=4 stillbirths; n=78 live births), respectively. With regard to children born large for gestational age, odds for a stillborn birth were 2.2 times higher for infants with birth weights >95th percentile born to women with T2D (n=15 stillbirths; n=402 live births). Furthermore, for mothers with T2D, a significantly higher proportion of stillbirths were male infants compared with the proportion for live births (81.1% vs 50.5%; P =.0002).

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Approximately one-third of stillbirths occurred at term, with rates peaking in the 38th week for mothers with T1D (7.0 per 1000 pregnancies) and in the 39th week for mothers with T2D (9.3 per 1000 pregnancies).

Several limitations were noted for this study, including its observational design and lack of information on important risk factors such as microvascular complications.

“Stillbirth rate remains high at term in women with diabetes in our population,” the researchers said, “and until more accurate prediction of at-risk pregnancies is available, earlier delivery may be considered an attractive option.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

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Reference

Mackin ST, Nelson SM, Wild SH, Colhoun HM, Wood R, Lindsay RS. Factors associated with stillbirth in women with diabetes [published online July 29, 2019]. Diabetologia. doi:10.1007/s00125-019-4943-9