Antepartum stillbirth is a complex syndrome associated with a range of risk factors, a prospective observational study has concluded.

Standardised pregnancy data were obtained from women taking part in the Newborn Cross-Sectional Study component of the INTERGROWTH-21st project. This was an international population-based study, covering a range of ethnic groups, carried out between 2009 and 2013.

There were 60,121 babies born to 59,052 women included in the study. Of these, 59,568 were liveborn

(57,508 singleton, 2,060 multiple) and 553 stillborn (511 singleton, 42 multiple). Of the stillbirths 445 (80%) were antepartum (413 singleton, 32 multiple).

Analysis revealed several demographic associations with increased risk of antepartum stillbirth.

Adjusted hazard ratios (AHR) were:

• Low socio-economic status AHR 1.6 (95% CI: 1.2-2.1)

• Single mother AHR 2.0 (95% CI: 1.4-2.8)

• Maternal age over 40 years AHR 2.2 (95% CI: 1.4-3.7)

Women with a previous stillbirth, preterm delivery, or delivery of a low or high birthweight baby (< 2,500 g or > 4,500 g) were also at increased risk of antepartum stillbirth.

No association between antepartum stillbirth and maternal smoking, illicit drug use or BMI was found.

Risk of stillbirth was greater in:

• Multiple pregnancies AHR 3.3 (95% CI: 2.0-5.6)

• Pregnancies complicated by antepartum haemorrhage AHR 3.3 (95% CI: 2.5-4.5).

Prior essential hypertension, pregnancy-induced hypertension,

preeclampsia and severe preeclampsia all increased risk too - AHR 3.98, 1.75, 3.23 and 5.53 respectively.

Those with fetal growth restriction (FGR) detected clinically, and then tracked either by ultrasound or serial abdominal measurements, had double the risk of antepartum stillbirth:

AHR 2.1 (95% CI: 1.4-3.1).

Stillborn babies were more likely to be small for gestational age (SGA) at birth, 16.7% vs 3.5% for liveborn babies:

AHR 4.6 (95% CI: 3.4-6.2).

In a sub-set of 4,607 women, considered at low risk for stillbirth, there were 18 antepartum stillbirths. There was no evidence of a decrease in growth velocity (measured by serial ultrasound head and abdominal circumference) in those who went on to be stillborn. They were ‘almost all within the 3rd and 97th centiles’.

Antepartum stillbirth is a complex and diverse syndrome. This study showed that poor fetal growth and SGA at birth, particularly when not suspected during pregnancy are associated with antepartum stillbirth. Serial ultrasound examinations in low-risk women failed to identify pregnancies at risk.

The study authors state: ‘Our findings reinforce recommendations to improve the detection and management of hypertensive disorders of pregnancy and other pregnancy conditions including the association with FGR.’

They add: ‘The promotion of interventions that are targeted at only one risk factor is unlikely to make a large impact on rates of antepartum stillbirth. Combinations of risk prediction models, biomarkers and growth trajectories could help to identify women at risk of specific forms of stillbirth.’