These numbers remain significant even after controlling for medical conditions.3
The utility of antepartum surveillance and induction of labor for delivery is unclear, given the risk of iatrogenic prematurity.
Risk of stillbirth is doubled among obese and markedly obese women
Although the number of adults who are overweight (BMI 25–30) has remained fairly constant over the past 20 years (30% to 35% of the population), the percentage of women of reproductive age who are obese (BMI >30) has risen markedly. Obesity is now present in 35% of the population, and marked obesity (BMI >40) affects an additional 6%. Both obese and markedly obese women face a twofold relative risk of stillbirth, compared with women of normal weight. The rate of stillbirth in this population is 12 to 18 for every 1,000 births—a 1.2% to 1.8% risk.
Although obesity-related stillbirth likely has multiple causes, the risk remains elevated even after exclusion of confounding factors such as smoking, gestational diabetes, and preeclampsia.
Race is an independent contributor
Racial differences in the rate of stillbirth remain despite a decrease in the overall stillbirth rate over the past 20 years ( FIGURE ). In 2003, the rate of stillbirth was 5 for every 1,000 births among non-Hispanic whites, 5.5 among Hispanics, and 12 among non-Hispanic blacks. In other words, the risk of stillbirth was 1 in 202, 1 in 183, and 1 in 87 births for white, Hispanic, and black women, respectively.
Willinger and colleagues utilized data from the National Center for Health Statistics and assessed 2001–2002 birth and infant death datasets for 36 states, examining the stillbirth hazard risk for more than 5 million singleton pregnancies. Stillbirth peaked at 20 to 23 weeks and 39 to 41 weeks’ gestation, as expected. However, at 20 to 23 weeks, the risk of stillbirth among non-Hispanic black women was more than twice the rate for non-Hispanic white women (RR, 2.8). Although it then declined as term approached, it remained greater than that of non-Hispanic white women (RR, 1.6).
FIGURE Racial disparities in the risk of stillbirth
Hazard of stillbirth for singleton pregnancies by gestational age and race and ethnicity, 2001–2002. SOURCE: Willinger et al. Greater acceptance and use of induction of labor at term among whites merits attention
In an editorial accompanying the study by Willinger and colleagues, Fretts pointed out the higher rate of induction of labor at term among white women that has been observed in at least three studies of vital statistics. (Willinger and colleagues also pointed out this difference.) The acceptance and use of labor induction at term—and the lower stillbirth rate—among white women warrants further investigation.
Education appears to reduce the risk of stillbirth to a greater degree among whites than it does among blacks. Again, nulliparity and advanced maternal age were important contributors to the risk of stillbirth across all three races.
WHAT THIS EVIDENCE MEANS FOR PRACTICE
Counsel African-American gravidas and women older than 35 years that their risk of stillbirth is elevated.
Obese women should be advised to lose weight before conception if at all possible to reduce the risk of stillbirth.
Needed: Standardized analysis
and documentation of stillbirth
Reddy UM, Goldberg R, Silver R, et al. Stillbirth classification—developing an international consensus for research: executive summary of a National Institute of Child Health and Human Development workshop. Obstet Gynecol. 2009;114:901–914.
Flenady V, Frøen JF, Pinar H, et al. An evaluation of classification systems for stillbirth. BMC Pregnancy Childbirth. 2009;9:24.
Further guidance for the clinical management of stillbirth will come from investigations of the underlying pathologies and associated risk factors. Key to development of this guidance is the involvement of obstetricians in documenting the antenatal record and delivery information. Also needed is a standardized system for recording this information. More than three dozen systems have been developed to classify stillbirth, at the expense of uniformity of content.
An international consensus group published guidelines on how to describe the cause of death in research endeavors, recognizing the need to maintain the ability to attach a level of uncertainty. In addition, Flenady and colleagues compared the most widely used systems in clinical practice, assigning the highest score for components such as ease of use, inter observer variability, and proportion of unexplained stillbirths to CODAC [cause of death and two associated causes]. This system assigns a primary cause of death from a specified list of choices and allows inclusion of two possible contributing causes.
Both the international consensus classification and the CODAC scoring system are accessible through links embedded within the articles. Both systems require the establishment of standardized evaluation and review of stillbirth that should include obstetricians, pathologists, and geneticists.