(1048) Population Attributable Risk Proportion of Modifiable and Non-modifiable Risk Factors for Stillbirth

Many risk factors are attributed to stillbirth, however, the exact proportion of stillbirths explained by these factors are unknown. We examined the proportions of stillbirths that are attributable to established modifiable and non-modifiable risk factors.

Study Design:

This is a retrospective case-control study. Eligible cases include women with stillbirths from January 2013 to July 2022. The cases were matched to controls based on the year of stillbirth and gestational age at the time of delivery. Stillbirths at or greater than 20 weeks gestation and fetal weight greater than or equal to 350 g if the gestational age is not known are  included. Stillbirths with congenital anomalies and chromosomal abnormalities and miscarriages before 20 weeks of gestation were excluded.

The risk factors selected for analysis were women less than 20 and greater than 35 years of age, non-Hispanic black race, BMI greater than 30, nulliparity, short inter pregnancy interval (less than 18 months), insufficient prenatal care (less than 3 prenatal visits), illicit substance use (alcohol and drug), smoking, preexisting medical conditions such as diabetes, hypertension and anemia and In vitro fertilization.  The main outcome measure is the population attributable risk proportion (PARP) of stillbirth. The PARP is calculated for individual risk factors.

Results:

There are 44,286 livebirths and 175 stillbirths (0.40%). 175 stillbirths and 154 controls were studied. Most of the women with stillbirths are between 20 to 35 years of age (77.7%), predominantly Caucasian (44.6%), 38% were between 20 to 25 weeks and 24% were between 36 to 40 weeks at diagnosis. When considering modifiable risk factors, insufficient prenatal care has the highest PARP% followed by age less than 20 , illicit substance use and diabetes (Table 1). The most important non- modifiable risk factor is nulliparity (Table 1).

Conclusion:

Changes to modifiable risk factor profiles especially focusing on insufficient prenatal care, teenage pregnancies, substance use disorders and diabetes could potentially reduce stillbirth rates.