Volume 201, Issue 5 , Pages 429-430, November 2009
The study of stillbirth
Article Outline
National health statistics help track trends in mortality and disease states and, in turn, governments have the opportunity to prioritize spending for research and ultimately to devise and implement prevention strategies.
See related article, page 469
The scope of stillbirth has been overlooked by many (Table) in part by an unconscious bias due to our lack of knowledge of the causes of fetal death, as well as the tendency to have a fatalistic view when death comes before birth. In both developed and developing countries, these deaths are often among the uncounted or somehow they “mean less.” It is certainly true that, in proportion to the number of deaths, there has been very little research on the specific causes of stillbirth. Moreover, the needed studies to guide clinical practice have not been done.
TABLE. Mortality in the United States 2004
| Variable | n |
|---|---|
| All deaths from AIDS | 15,790 |
| Deaths due to acute and chronic viral hepatitis | 3000 |
| Infant deaths due to congenital malformations and chromosomal abnormalities | 5622 |
| Deaths due to sudden infant death | 2246 |
| Postnatal deaths due to short gestation | 4642 |
| Stillbirths | 26,655 |
In general, the potential risk of stillbirth is not a topic that is often shared with parents because it scares them, coupled with the view that many of these deaths are accidents that could not have been avoided. Obstetricians, for example, spend resources to screen for human immunodeficiency virus and hepatitis B and considerable time is routinely spend on reviewing the risks and benefits for screening strategies for congenital anomalies and Down syndrome in all women, even though the risk of these conditions are equivalent or lower than for stillbirth.
In this month's Journal, Willinger et al1 have drilled into the National Health Statistics to present a long overdue assessment of race and stillbirth. In 2001-2002, the chance that a white woman would have a stillbirth was 1/202; for a Hispanic woman this risk was 1/183 and for a black woman the rate was 1/87.
An obvious strength of the study is its large size (5,138,122 singleton births). The authors were able to stratify by multiple variables, including race, gestational age, education, parity, and the presence or absence of obstetric, fetal, or medical conditions. There are the expected observations that black women are more likely than white women to be younger, are less likely to have higher education, are more likely to be parous, and have a higher probability of having maternal medical conditions reported. Among all women, nulliparous women were at a 60-70% increased risk when compared to multiparous women. But the authors were also able to assess the role of maternal age and education on disparities between black and white women. They found that while education confers a protective effect for white women, there was minimal effect for black or Hispanic women. This raises many questions, not the least of which is whether there is a biological explanation for this racial disparity or it is an effect due to differential quality of care.
Notably, the black/white hazard ratio for women ≥35 years of age was higher preterm than term. Prior to 37 weeks black women had about a 2.8-fold increased risk of stillbirth when compared to white women. After 37 weeks the hazard ratio demonstrated a 1.7-fold increased risk for black women over white women. White women were more likely to have congenital anomalies or fetal growth restriction in the preterm stillbirths whereas black women were more likely to have labor-related conditions.
The sole figure in the Willinger et al1 article tells a powerful story. Hispanic and white women share a very similar risk of stillbirth throughout pregnancy, with a notable increased risk (0.4/1000) from 20-24 weeks of gestation, then the rates remain relatively low (0.2/1000) until about 36 weeks when the rate begins to steadily climb to a high of about 0.9/1000 at 41 weeks. Black women, however, have a higher rate of stillbirth at every gestational age. Between 20-24 weeks of gestation the hazard rate is 1.1/1000; this declines to about 0.4/1000 during the weeks 25-36 and increases to a high of 1.35/1000 at 41 weeks. The causes of stillbirth in these early gestational ages are often quite different, with infection, congenital anomalies, and abruption the leading causes of preterm stillbirth.2 Much research is still needed to delineate the biological and modifiable risk factors that increase the risk for black women. Stillbirths late in pregnancy are often not associated with traditional pregnancy problems such has hypertension and diabetes but often remain unexplained even after thorough evaluation.2
The question remains whether black women without other risk factors should be treated as high risk late in pregnancy and offered increased surveillance or timed delivery prior to the typical postdates period. It is interesting, however, that while black women have more than twice the risk of stillbirth than white women, they are less likely to undergo an induction of labor (17.5% vs 24.6%).3 Using US data between 1991-1997 for inductions in singleton pregnancies, Yuan et al4 found that the rates of labor induction between 40-43 weeks increased from 13% of deliveries to 22% for white women, while the rates for black women only increased from 8.4-15%. During that study period the cesarean section remained at 21%, but there was a 20% reduction of stillbirths experience by white women. This reduction could be largely attributed to the role of induction. A similar benefit of induction was not found for black women but these authors thought that the induction rate may not have been high enough to detect a difference.4 One may argue that the increase in the number of inductions is unwarranted, but this risk-benefit analysis has not been done, nor has an analysis evaluated the risk-benefit ratio differentials for black and white women. It is not certain why there was a difference in induction rates. Possible explanations include a failure to frame race as a risk factor for late stillbirth; less than optimal vigilance for black women; or a failure to collaborate with black women so that an induction becomes an acceptable intervention.
More than 30 years ago, research and death scene analysis identified modifiable risk factors for sudden infant death such as prone sleeping and smoking. Public awareness and education have reduced sudden infant death by >60% over a decade. It is time now to give stillbirth equal recognition. The fatalistic view that these deaths cannot be prevented has reduced our opportunity to do so. Perinatal audit of stillbirth typically identifies that 30-40% of stillbirths have received suboptimal care with the most common being the failure to identify fetal growth restriction, failure to identify and manage medical risk factors, and the failure to optimally manage decreased fetal movements.5, 6 Willinger et al1 have identified key areas for further research, the biology of the disproportionate losses of stillbirths in black women early in pregnancy, and the evaluation of risk factors at or near term.
References
- . Racial disparities in stillbirth across gestation in the United States. Am J Obstet Gynecol. 2009;201:469.e1–469.e8
- . Etiology and prevention of stillbirth. Am J Obstet Gynecol. 2005;196:1923–1935
- . Birth data final 2004. Natl Vital Stat Rep. 2006;55:1–101
- . Fetal deaths in the United States 1997-1991. Am J Obstet Gynecol. 2005;193:489–495
- . Suboptimal care in stillbirths–a retrospective audit study. Acta Obstet Gynecol. 2007;86:444–450
- . Differences in perinatal mortality and suboptimal care between 10 European regions: results of an international audit. BJOG. 2003;110:97–105
- . Deaths: final data for 2004. http://www.cdc.gov/nchs/products/pubs/pubd/hestats/finaldeaths04/finaldeaths04_tables.pdf#1Accessed July 23, 2009
- . Disease burden from viral hepatitis A, B and C in the United States. http://www.cdc.gov/hepatitis/Statistics.htmAccessed July 22, 2009
Reprints not available from the author.
PII: S0002-9378(09)00702-9
doi:10.1016/j.ajog.2009.06.058
© 2009 Mosby, Inc. All rights reserved.
Refers to article:
-
Racial disparities in stillbirth risk across gestation in the United States
, 18 September 2009
Volume 201, Issue 5 , Pages 429-430, November 2009
