Placenta previa: Its relationship with race and the country of origin among Asian women

Abstract

Objectives. To examine the association between placenta previa with maternal race and its variations by country of origin among Asian women. Study design. Retrospective cohort study. Methods. We analyzed data from a population-based retrospective cohort study of 16,751,627 pregnancies in the US. The data were derived from the national linked birth/infant mortality database for the period 1995Á2000. Multiple logistic regressions were used to describe the relationship between placenta previa and race as well as country of origin among Asian women. Results. About 3.3 per 1,000 pregnancies were complicated with placenta previa among white women, while the corresponding figures for black women and women of other races were 3.0 and 4.5 per 1,000 pregnancies, respectively. The excess risk remained substantial and significant after adjustment for confounders for women of other races compared to white women. The frequencies of placenta previa among Chinese, Japanese, Filipino, Asian Indian, Korean, Vietnamese and other Asian or Pacific Islander were 5.6, 5.1, 7.6, 4.5, 5.9, 4.4 and 4.4 per 1,000 pregnancies, respectively. The adjusted odds ratios ranged from 1.39 to 2.15 among Asian women by country of origin, with the lowest for Japanese and Vietnamese and the highest for Filipino women in our study. Conclusion. Asian women have excess risk of placenta previa compared with white women. Major variation exists in placenta previa risk among Asian women, with the lowest risk in Japanese and Vietnamese women and the highest risk in Filipino women.

Racial and ethnic differences in the prevalence of placenta previa

“…Although the Shen et al 16 study did include Hispanic women, as did our study, they reported that African-American women were at a higher risk of placenta previa then Asian women, in contrast to our result that Asian women had the highest risk of placenta previa followed by African-American women. Furthermore, the overall lower prevalence of placenta previa in the Taylor et al 14 and Yang et al 15 studies suggest that the information they derived from birth certificate data may have underreported placenta previa. The relationship between race and ethnicity and the development of placenta previa is poorly understood.…”

“…8,11,13,18,21,22 Other studies failed to include a separate category for Asian 17 or Hispanic women, 15 or had limited comparisons of only Asian and Caucasian women, but not African-American or Hispanic women.…”

“…The studies by Yang et al 15 and Shen et al 16 were larger retrospective cohort studies using the US national-linked birth/infant mortality database and the National Inpatient Sample, respectively. However, the Yang et al 15 study was limited by the absence of a Hispanic ethnic category, and their results differed from ours in that they showed African-American women had a lower frequency of placenta previa (3.0/1000) then Caucasian women (3.3/1000), compared with our study which found African-American women had a higher frequency of placenta previa (4.4/1000) compared with Caucasian women (3.6/1000). Although the Shen et al 16 study did include Hispanic women, as did our study, they reported that African-American women were at a higher risk of placenta previa then Asian women, in contrast to our result that Asian women had the highest risk of placenta previa followed by African-American women.…”

“…8,9,11,19 -23 The two largest studies to date on race and placenta previa were population-based retrospective cohort studies with data derived from US national databases, and although both agreed that Asian women had a higher risk of placenta previa compared with Caucasian women, they reached opposite conclusions regarding African-American women. 15,16 (See Appendix 1, Supplementary Information, for a summary of the literature.) Given these discrepancies in the literature regarding the relationship between maternal race and placenta previa, we sought to determine the prevalence of placenta previa stratified by race and ethnicity, using a large northern Californian Health Maintenance Organization birth cohort from 1995 to 2006, and to identify whether any of the five major racial and ethnic groups studied (African American, Asian, Caucasian, Hispanic and Native American) were associated with an increased risk of placenta previa.…”

“…[8][9][10][11][12][13] However, there is conflicting data regarding whether specific racial or ethnic groups are associated with an increased risk for placenta previa and the biologic plausibility of such an association is unclear. Several studies have found an increased risk of placenta previa among Asian women compared with Caucasian women, [14][15][16] and among African-American and/or other minority women pooled into a mixed group than for Caucasian women. 2,8,13,16 -18 In contrast, other studies failed to show a relationship between maternal race and placenta previa.…”