Comparison of adverse perinatal outcomes between Asians and Caucasians: a population-based retrospective cohort study in Ontario.

BACKGROUND: Racial disparities in adverse perinatal outcomes have been studied in other countries, but little has been done for the Canadian population. In this study, we sought to examine the disparities in adverse perinatal outcomes between Asians and Caucasians in Ontario, Canada. METHODS: We conducted a population-based retrospective cohort study that included all Asian and Caucasian women who attended a prenatal screening and resulted in a singleton birth in an Ontario hospital (April 1st, 2015-March 31st, 2017). Generalized estimating equation models were used to estimate the independent adjusted relative risks and adjusted risk difference of adverse perinatal outcomes for Asians compared with Caucasians. RESULTS: Among 237,293 eligible women, 31% were Asian and 69% were Caucasian. Asians were at an increased risk of gestational diabetes mellitus, placental previa, early preterm birth (< 32 weeks), preterm birth, emergency cesarean section, 3rd and 4th degree perineal tears, low birth weight (< 2500 g, < 1500 g), small-for-gestational-age (<10th percentile, <3rd percentile), neonatal intensive care unit admission, and hyperbilirubinemia requiring treatment, but had lower risks of preeclampsia, macrosomia (birth weight > 4000 g), large-for-gestational-age neonates, 5-min Apgar score < 7, and arterial cord pH ≤7.1, as compared with Caucasians. No difference in risk of elective cesarean section was observed between Asians and Caucasians. CONCLUSION: There are significant differences in several adverse perinatal outcomes between Asians and Caucasians. These differences should be taken into consideration for clinical practices due to the large Asian population in Canada.

Racial and ethnic differences in the prevalence of placenta previa.

OBJECTIVE: The objective of this study is to determine the prevalence of placenta previa among different racial and ethnic groups. STUDY DESIGN: We conducted a retrospective cohort study to examine the prevalence of placenta previa among five major racial and ethnic groups: African American, Asian, Caucasian, Hispanic and Native American. We included all deliveries ≥ 20 weeks gestation from a large northern Californian Health Maintenance Organization from 1995-2006. A multivariable logistic regression model was used to control for potential confounders. RESULT: Of the 394 083 deliveries in our cohort, 1580 (0.40%) were complicated by placenta previa. The prevalence of placenta previa was: Asian 0.64%, Native American 0.60%, African American 0.44%, Caucasian 0.36%, Hispanic 0.34% and unknown 0.31% (P<0.001). In our multivariable logistic regression model, only Asians (odds ratio (OR) 1.73, 95% confidence intervals (CI) 1.53-1.95) and African Americans (OR 1.43, 95% CI 1.19-1.72) were at increased risk for having placenta previa, compared with Caucasians. CONCLUSION: Asian women have the highest prevalence of placenta previa.

Comparison of risk factors for placental abruption and placenta previa: case-cohort study.

AIM: A case-cohort study was performed to clarify and compare the risk factors for placental abruption and placenta previa. MATERIAL & METHODS: This study reviewed 242,715 births at 125 centers of the perinatal network in Japan from 2001 through to 2005 as a base-cohort. Women with singleton pregnancies delivered after 22 weeks of gestation were included. The evaluation determined the risk factors for placental abruption and placenta previa. Five thousand and thirty-six births (2.1%) were determined as the subcohort by random selection. Acute-inflammation-associated clinical conditions (premature rupture of membranes and clinical chorioamnionitis) and chronic processes associated with vascular dysfunction or chronic inflammation (chronic and pregnancy-induced hypertension, pre-existing or gestational diabetes and maternal smoking) was examined between the two groups. RESULTS: Placental abruption and placenta previa were recorded in 10.1 per 1000 and 13.9 per 1000 singleton births. Risk factors for abruption and previa, respectively, included maternal age over 35 years (adjusted risk ratios [RRs]=1.20 and 1.78), IVF-ET (RRs = 1.38 and 2.94), preterm labor (RRs = 1.63 and 3.09). Smoking (RRs = 1.37), hypertension (RRs = 2.48), and pregnancy-induced hypertension (RR = 4.45) were risk factors for abruption but not for previa. On the other hand, multiparity (RR= 1.18) was a risk factor for previa but not for abruption. The rates of acute-inflammation-associated conditions and chronic processes were higher among women with abruption than with previa. (RR 2.0 and 4.08, respectively). CONCLUSION: The case-cohort study technique elucidated the difference in the risk factors for placental abruption and placenta previa.

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

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 1995-2000. 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 variation in the frequency of intrapartum hemorrhage.

OBJECTIVE: To evaluate racial variation in the frequency of intrapartum hemorrhage. METHODS: Using information from birth certificates of live singleton births in North Carolina from 1990 to 1997 (n = 807,759), we evaluated the frequency of intrapartum hemorrhage and its association with maternal race. Logistic regression models were used to evaluate the risk of any intrapartum hemorrhage, placental abruption, placenta previa, and unspecified hemorrhage in each racial group, adjusted for other risk factors. RESULTS: Black women had the highest rates of any hemorrhage (1.52% black, 1.47% white, 1.33% other race, P =.006) and placental abruption (0.79% black, 0.68% white, 0.56% other race, P =.001) but had lower rates of unspecified hemorrhage (0.37% black, 0.42% white, 0.42% other race, P =.001). Race was not associated with placenta previa. Maternal race remained associated with intrapartum hemorrhage after multivariable analysis, but the direction of the association was reversed. Black women were less likely to have any intrapartum hemorrhage (odds ratio [OR] 0.80, 95% confidence interval [CI] 0.77, 0.85), placental abruption (OR 0.76, 95% CI 0.70, 0.82), placenta previa (OR 0.89, 95% CI 0.81, 0.98), or other unspecified hemorrhage (OR 0.84, 95% CI 0.76, 0.92) compared with white women. Women of other minority races were at lower risk for placental abruption (OR 0.76, 95% CI 0.67, 0.87) but were comparable to white women for risk of placenta previa (OR 1.06, 95% CI 0.91, 1.24) and other unspecified hemorrhage (OR 1.02, 95% CI 0.88, 1.19). CONCLUSION: Although black women had higher rates of intrapartum hemorrhage than whites, the increased frequency was attributable to differences in clinical presentation and other risk factors.

Placenta previa: obstetric risk factors and pregnancy outcome.

OBJECTIVE: To determine the incidence, obstetric risk factors and perinatal outcome of placenta previa. STUDY DESIGN: All singleton deliveries at our institution between 1990 and 1998 complicated with placenta previa were compared with those without placenta previa. RESULTS: Placenta previa complicated 0.38% (n = 298) of all singleton deliveries (n = 78 524). A back-step multiple logistic regression model found the following factors to be independently correlated with the occurrence of placenta previa: maternal age above 40 years (OR 3.1, 95% CI 2.0-4.9), infertility treatments (OR 3.1, 95% CI 1.8-5.6), a previous Cesarean section (OR 1.8, 95% CI 1.4-2.4), a history of habitual abortions (OR 1.3, 95% CI 1.3-2.7) and Jewish ethnicity (OR 1.3, 95% CI 1.1-1.8). Pregnancies complicated with placenta previa had significantly higher rates of second-trimester bleeding (OR 156.0, 95% CI 87.2-277.5), pathological presentations (OR 7.6, 95% CI 5.7-10.1), abruptio placentae (OR 13.1, 95% CI 8.2-20.7), congenital malformations (OR 2.6, 95% CI 1.5-4.2), perinatal mortality (OR 2.6, 95% CI 1.1-5.6), Cesarean delivery (OR 57.4, 95% CI 40.7-81.4), Apgar scores at 5 min lower than 7 (OR 4.4, 95% CI 2.3-8.3), placenta accreta (OR 3.6, 95% CI 1.1-9.9) postpartum hemorrhage (OR 3.8, 95% CI 1.2-10.5), postpartum anemia (OR 5.5, 95% CI 4.4-6.9) and delayed maternal and infant discharge from the hospital (OR 10.9, 95% CI 7.3-16.1) as compared to pregnancies without placenta previa. In a multivariable analysis investigating risk factors for perinatal mortality, the following were found to be independent significant factors: congenital malformations, placental abruption, pathological presentations and preterm delivery. In contrast, placenta previa and Cesarean section were found to be protective factors against the occurrence of perinatal mortality while controlling for confounders. CONCLUSION: Although an abnormal implantation per se was not an independent risk factor for perinatal mortality, placenta previa should be considered as a marker for possible obstetric complications. Hence, the detection of placenta previa should encourage a careful evaluation with timely delivery in order to reduce the associated maternal and perinatal complications.

Increased risk of placenta previa among women of Asian origin.

OBJECTIVE: To investigate the frequency of placenta previa among Asian women. METHODS: We conducted a population-based case-control study using Washington state birth certificate data from 1984-1987. Our study population included 810 women with pregnancies complicated by placenta previa and 2917 randomly selected controls. Unconditional logistic regression was used to estimate odds ratios (OR) and their 95% confidence intervals (CI), and interaction terms were used to examine effect modification. Potential confounding by maternal age, gravidity and parity, maternal smoking during pregnancy, and a history of abortion or cesarean delivery was adjusted for in the analysis. RESULTS: The frequency of placenta previa during the study period was 3.3 per 1000 live births. Women of Asian origin were 86% more likely (OR 1.86, 95% CI 1.38-2.51) to have a delivery complicated by placenta previa than were white women. This association was stronger among women without a previous live birth (OR 2.51, 95% CI 1.57-4.01) than those who previously had experienced a live birth (OR 1.50, 95% CI 1.01-2.25). CONCLUSION: Asian women residing in the United States are at increased risk of placenta previa. If confirmed by others, our results suggest that obstetricians should consider meticulous ultrasound evaluations during pregnancy to rule out the presence of placenta previa in Asian-American women.