In the United Kingdom, 89 women of every 100,000 who gave birth in 2005–2006 experienced at least one of five serious pregnancy-related conditions. The rate was significantly higher among black women than among whites, and analyses that controlled for a range of risk factors confirmed that nonwhite women overall have a higher risk of maternal morbidity than their white counterparts.1 Maternal deaths are infrequent in the United Kingdom, as they are in most developed countries; therefore, the analysts reasoned that studying severe maternal morbidity—which occurs more frequently than maternal mortality—may shed additional light on the pregnancy experiences of different subgroups of women.
Data came from a national surveillance system that asks clinicians in hospital maternity units to report monthly on whether they have seen any women with certain rare, serious conditions, including women who have died. Five conditions that can lead to pregnancy-related deaths were considered in the analyses of severe maternal morbidity: acute fatty liver of pregnancy (a buildup of fat in the liver), amniotic fluid embolism (the presence of amniotic fluid, fetal cells or other debris in the woman's circulatory system), pulmonary embolism, eclampsia (characterized by convulsions during pregnancy or the first 10 days after delivery, followed by specified clinical events) or hysterectomy at the time of delivery. If an occurrence of any of these conditions was reported, clinicians were sent a form asking for details about the diagnosis and about women's background characteristics (including self-reported ethnicity) and risk factors for maternal morbidity.
Between February 2005 and February 2006, some 686 of the 775,186 women who gave birth in the United Kingdom experienced one of the conditions included in the analyses. Seventy-four percent of the women with one of these conditions were white, 3% Indian, 5% Pakistani, 2% Bangladeshi, 2% black African, 7% black Caribbean and 7% members of other ethnic groups. Their median age was 31, and four in 10 had not given birth before.
The rate of severe maternal morbidity was 89 per 100,000 births overall, but it varied significantly among ethnic groups. White women had a rate of 80 per 100,000, whereas nonwhites as a group had a rate of 126 per 100,000. Black women had the highest rates—188 and 196 per 100,000 among those of African and Caribbean origin, respectively. Pakistanis also had a significantly higher rate than whites (119 per 100,000 births). Rates appeared to be elevated in each of the other minority ethnic groups as well, but these groups were small, and the differences were not statistically significant. Peripartum hysterectomy was the most common of the conditions, accounting for nearly half of reported cases. No ethnic differences were apparent in the distribution of severe pregnancy-related conditions.
Results of a logistic regression analysis that controlled for women's background characteristics and risk factors demonstrated that nonwhite women (who were examined as a group because of the small numbers in some subgroups) were significantly more likely than white women to experience severe maternal morbidity (odds ratio, 1.5). Other characteristics associated with women's likelihood of having had one of the five conditions studied were being younger than 20 or older than 34 (2.6 and 1.8, respectively) and low socioeconomic status (1.3).
The analysts point out two characteristics of their study that could be viewed as limitations: They studied only selected conditions among those that are major direct causes of maternal deaths in the United Kingdom; and because national data on maternal ethnicity were not available, they had to estimate ethnicity for 25% of women included in the analyses. However, they note that evidence in the literature suggests that effects on their results were likely not substantial.
Commenting on the ethnic differences they found in the risk of severe maternal morbidity, the analysts speculate that the causes may lie in ethnic differences in risk factors or in the care women receive during pregnancy, labor and delivery. This possibility, they conclude, "highlights to clinicians and policy makers the importance of tailored maternity services and improved access to care for women from ethnic minorities."
1. Knight M et al., Inequalities in maternal health: national cohort study of ethnic variation in severe maternal morbidities, BMJ, 2009, 338:b542, DOI: doi:10.1136/bmj.b542, accessed Mar. 27, 2009.