A Population-based Study of Race-specific Risk for Placental Abruption
A Population-based Study of Race-specific Risk for Placental Abruption
Background: Efforts to elucidate risk factors for placental abruption are imperative due to the severity of complications it produces for both mother and fetus, and its contribution to preterm birth. Ethnicity-based differences in risk of placental abruption and preterm birth have been reported. We tested the hypotheses that race, after adjusting for other factors, is associated with the risk of placental abruption at specific gestational ages, and that there is a greater contribution of placental abruption to the increased risk of preterm birth in Black mothers, compared to White mothers.
Methods: We conducted a population-based cohort study using the Missouri Department of Health's maternally-linked database of all births in Missouri (1989-1997) to assess racial effects on placental abruption and the contribution of placental abruption to preterm birth, at different gestational age categories (n = 664,303).
Results: Among 108,806 births to Black mothers and 555,497 births to White mothers, 1.02% (95% CI 0.96-1.08) of Black births were complicated by placental abruption, compared to 0.71% (95% CI 0.69-0.73) of White births (aOR 1.32, 95% CI 1.22-1.43). The magnitude of risk of placental abruption for Black mothers, compared to White mothers, increased with younger gestational age categories. The risk of placental abruption resulting in term and extreme preterm births (< 28 weeks) was higher for Black mothers (aOR 1.15, 95% CI 1.02-1.29 and aOR 1.98, 95% CI 1.58-2.48, respectively). Compared to White women delivering in the same gestational age category, there were a significantly higher proportion of placental abruption in Black mothers who delivered at term, and a significantly lower proportion of placental abruption in Black mothers who delivered in all preterm categories (p < 0.05).
Conclusion: Black women have an increased risk of placental abruption compared to White women, even when controlling for known coexisting risk factors. This risk increase is greatest at the earliest preterm gestational ages when outcomes are the poorest. The relative contribution of placental abruption to term births was greater in Black women, whereas the relative contribution of placental abruption to preterm birth was greater in White women.
Placental abruption, defined as premature separation of a normally implanted placenta prior to delivery, results from the culmination of underlying pathophysiologic processes that may either be initiated by a single precipitating event (e.g. premature rupture of membranes), or, more commonly, associated with chronic uteroplacental vascular insufficiency (e.g. chronic hypertension). Placental abruption complicates 0.8 to 1.0% of pregnancies, and the incidence appears to be increasing. Furthermore, histologic evidence of decidual hemorrhage has been noted in 2 to 4% of deliveries, even though most cases are not associated with clinical diagnoses of abruption.
Placental abruption, especially marginal or peripheral placental abruption, has also been associated with preterm labor. The incidence of abruption peaks at 24 to 26 weeks of gestation. Furthermore, histologic evidence of old hemorrhage was demonstrated in the placentas of over 50% of women with preterm birth (PTB) in one analysis. Interestingly, there appears to be evidence for heterogeneity in the clinical pathways of placental abruption in term and preterm gestations, with acute inflammation more prevalent at preterm than term gestations, and chronic processes present throughout gestation. Risk factors associated with placental abruption comprise previous abruption (strongest risk factor), mechanical factors (i.e. trauma), chronic hypertension, gestational hypertension, cigarette smoking, cocaine use, preterm premature rupture of fetal membranes (PPROM), multiparity, multiple gestations, advanced maternal age, inherited thrombophilias, and polyhydramnios.
Differences in risk of placental abruption based on ethnicity have also been reported. Placental abruption is more common among African-American women (1 in 595) than among White (1 in 876) or Latin-American (1 in 1423) women. Furthermore, the rate of abruption has increased 92% among Black women between 1979-1981 (0.76%) and 1999-2001 (1.43%), whereas the rate increased by 15% among White women over the same period (0.82% in 1979-1981 to 0.94% in 1999-2001).
The influence of maternal race on the risk for PTB has been demonstrated in many studies. Black women who have had a PTB are disproportionately at higher risk for subsequent PTB than White women, and this difference in risk based on ethnicity is not adequately explained by socioeconomic status (SES) or access to health care. Since Black maternal race is a risk factor for placental abruption as well as PTB, and placental abruption is associated with PTB, we would expect a greater contribution of placental abruption to the increased risk of PTB in Black mothers. However, epidemiological studies to date that have examined racial disparity in placental abruption at different gestational age categories are lacking.
The Missouri Department of Health's maternally linked birth-death certificate database is a unique and comprehensive resource for assessing birth outcomes across racial, SES and maternal medical risk factors. Using this database to analyze potential racial, SES and medical contributors to the occurrence of placental abruption, we tested the hypothesis that race, while adjusting for other known risk factors, is associated with the risk of placental abruption. Furthermore, we proceeded to estimate the relative contribution of placental abruption to PTB in Black and White mothers, testing the hypothesis that there is a greater contribution of placental abruption to the increased risk of PTB in Black mothers, compared to White mothers.
Background: Efforts to elucidate risk factors for placental abruption are imperative due to the severity of complications it produces for both mother and fetus, and its contribution to preterm birth. Ethnicity-based differences in risk of placental abruption and preterm birth have been reported. We tested the hypotheses that race, after adjusting for other factors, is associated with the risk of placental abruption at specific gestational ages, and that there is a greater contribution of placental abruption to the increased risk of preterm birth in Black mothers, compared to White mothers.
Methods: We conducted a population-based cohort study using the Missouri Department of Health's maternally-linked database of all births in Missouri (1989-1997) to assess racial effects on placental abruption and the contribution of placental abruption to preterm birth, at different gestational age categories (n = 664,303).
Results: Among 108,806 births to Black mothers and 555,497 births to White mothers, 1.02% (95% CI 0.96-1.08) of Black births were complicated by placental abruption, compared to 0.71% (95% CI 0.69-0.73) of White births (aOR 1.32, 95% CI 1.22-1.43). The magnitude of risk of placental abruption for Black mothers, compared to White mothers, increased with younger gestational age categories. The risk of placental abruption resulting in term and extreme preterm births (< 28 weeks) was higher for Black mothers (aOR 1.15, 95% CI 1.02-1.29 and aOR 1.98, 95% CI 1.58-2.48, respectively). Compared to White women delivering in the same gestational age category, there were a significantly higher proportion of placental abruption in Black mothers who delivered at term, and a significantly lower proportion of placental abruption in Black mothers who delivered in all preterm categories (p < 0.05).
Conclusion: Black women have an increased risk of placental abruption compared to White women, even when controlling for known coexisting risk factors. This risk increase is greatest at the earliest preterm gestational ages when outcomes are the poorest. The relative contribution of placental abruption to term births was greater in Black women, whereas the relative contribution of placental abruption to preterm birth was greater in White women.
Placental abruption, defined as premature separation of a normally implanted placenta prior to delivery, results from the culmination of underlying pathophysiologic processes that may either be initiated by a single precipitating event (e.g. premature rupture of membranes), or, more commonly, associated with chronic uteroplacental vascular insufficiency (e.g. chronic hypertension). Placental abruption complicates 0.8 to 1.0% of pregnancies, and the incidence appears to be increasing. Furthermore, histologic evidence of decidual hemorrhage has been noted in 2 to 4% of deliveries, even though most cases are not associated with clinical diagnoses of abruption.
Placental abruption, especially marginal or peripheral placental abruption, has also been associated with preterm labor. The incidence of abruption peaks at 24 to 26 weeks of gestation. Furthermore, histologic evidence of old hemorrhage was demonstrated in the placentas of over 50% of women with preterm birth (PTB) in one analysis. Interestingly, there appears to be evidence for heterogeneity in the clinical pathways of placental abruption in term and preterm gestations, with acute inflammation more prevalent at preterm than term gestations, and chronic processes present throughout gestation. Risk factors associated with placental abruption comprise previous abruption (strongest risk factor), mechanical factors (i.e. trauma), chronic hypertension, gestational hypertension, cigarette smoking, cocaine use, preterm premature rupture of fetal membranes (PPROM), multiparity, multiple gestations, advanced maternal age, inherited thrombophilias, and polyhydramnios.
Differences in risk of placental abruption based on ethnicity have also been reported. Placental abruption is more common among African-American women (1 in 595) than among White (1 in 876) or Latin-American (1 in 1423) women. Furthermore, the rate of abruption has increased 92% among Black women between 1979-1981 (0.76%) and 1999-2001 (1.43%), whereas the rate increased by 15% among White women over the same period (0.82% in 1979-1981 to 0.94% in 1999-2001).
The influence of maternal race on the risk for PTB has been demonstrated in many studies. Black women who have had a PTB are disproportionately at higher risk for subsequent PTB than White women, and this difference in risk based on ethnicity is not adequately explained by socioeconomic status (SES) or access to health care. Since Black maternal race is a risk factor for placental abruption as well as PTB, and placental abruption is associated with PTB, we would expect a greater contribution of placental abruption to the increased risk of PTB in Black mothers. However, epidemiological studies to date that have examined racial disparity in placental abruption at different gestational age categories are lacking.
The Missouri Department of Health's maternally linked birth-death certificate database is a unique and comprehensive resource for assessing birth outcomes across racial, SES and maternal medical risk factors. Using this database to analyze potential racial, SES and medical contributors to the occurrence of placental abruption, we tested the hypothesis that race, while adjusting for other known risk factors, is associated with the risk of placental abruption. Furthermore, we proceeded to estimate the relative contribution of placental abruption to PTB in Black and White mothers, testing the hypothesis that there is a greater contribution of placental abruption to the increased risk of PTB in Black mothers, compared to White mothers.
