Increased risk of placenta previa among women of Asian origin

Iron deficiency anaemia associated with increased placenta praevia and placental abruption: a retrospective case-control study

BACKGROUND/OBJECTIVES

A few studies reported association between placenta praevia (PP) and placental abruption (PA) with maternal iron deficiency anaemia (IDA), which is not an established risk factor for these conditions. This retrospective case-control study was performed to determine the relationship between IDA with PP and PA.

METHODS

Maternal characteristics, risk factors for and incidence of antepartum haemorrhage overall, and PP and PA, were compared between women with IDA only and controls without IDA or haemoglobinopathies matched for exact age and parity (four controls to each index case), who carried singleton pregnancy to ≥22 weeks and managed under our care from 1997 to 2019.

RESULTS

There were 1,176 women (0.8% of eligible women in the database) with IDA only, who exhibited slightly but significantly different maternal characteristics, and increased antepartum haemorrhage overall (3.4% versus 2.2%, p = 0.031, OR 1.522, 95% CI 1.037-2.234) and PP (1.8% versus 0.9%, p = 0.010, OR 1.953, 95% CI 1.164-3.279), but not PA (1.2% versus 1.1%, p = 0.804, OR 1.077, 95% CI 0.599-1.936). When stratified by parity status, increased PP was found in nulliparous women only. On multivariate analysis adjusting for parity, previous abortion history, overweight and obesity, short stature, other antenatal complications as a composite factor, preterm (<37) delivery, previous caesarean delivery, and infant gender, IDA was associated with PP (aOR 3.485, 95% CI 1.959-6.200) and PA (aOR 2.181, 95% CI 1.145-4.155).

CONCLUSIONS

Both PP and PA are increased in women with IDA, the prevention of which could be a means to reduce the occurrence of both PP and PA.

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.

Smoking and placenta previa: a meta-analysis

OBJECTIVE

Previous studies found a positive association between placenta previa and smoking during pregnancy. However, the results of these studies are inconsistent. The aim was to perform meta-analysis of the association between smoking during pregnancy and placenta previa.

METHODS

Major electronic databases, including PubMed, Web of Science, and Scopus were searched until June 2015. The heterogeneity across studies was explored by Q-test and I² statistic. The possibility of publication bias was assessed using Begg's and Egger's tests. The results were reported using odds ratio (OR) estimate with its 95% confidence intervals using a random-effects model.

RESULTS

The literature search yielded 991 publications until October 2015 with 9,094,443 participants. Based on the random effect model, compared to nonsmoker women, the estimated OR and RR of placenta previa was 1.42 (95% CI: 1.30, 1.54) and 1.27 (95% CI: 1.18, 1.35), respectively.

CONCLUSIONS

There is sufficient documents based on the observational studies that smoking during pregnancy is significantly associated with an increased risk of placenta previa. Therefore, smoking during pregnancy can be considered as a predictor of placenta previa.

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.

Risk of placenta previa in second birth after first birth cesarean section: a population-based study and meta-analysis

BACKGROUND

OBJECTIVE

To compare the risk of placenta previa at second birth among women who had a cesarean section (CS) at first birth with women who delivered vaginally.

METHODS

Retrospective cohort study of 399,674 women who gave birth to a singleton first and second baby between April 2000 and February 2009 in England. Multiple logistic regression was used to adjust the estimates for maternal age, ethnicity, deprivation, placenta previa at first birth, inter-birth interval and pregnancy complications. In addition, we conducted a meta-analysis of the reported results in peer-reviewed articles since 1980.

RESULTS

The rate of placenta previa at second birth for women with vaginal first births was 4.4 per 1000 births, compared to 8.7 per 1000 births for women with CS at first birth. After adjustment, CS at first birth remained associated with an increased risk of placenta previa (odds ratio = 1.60; 95% CI 1.44 to 1.76). In the meta-analysis of 37 previously published studies from 21 countries, the overall pooled random effects odds ratio was 2.20 (95% CI 1.96-2.46). Our results from the current study is consistent with those of the meta-analysis as the pooled odds ratio for the six population-based cohort studies that analyzed second births only was 1.51 (95% CI 1.39-1.65).

CONCLUSIONS

There is an increased risk of placenta previa in the subsequent pregnancy after CS delivery at first birth, but the risk is lower than previously estimated. Given the placenta previa rate in England and the adjusted effect of previous CS, 359 deliveries by CS at first birth would result in one additional case of placenta previa in the next pregnancy.

Maternal morbidity and perinatal outcomes among foreign-born Cambodian, Laotian, and Vietnamese Americans in Washington State, 1993-2006

This study examined differences in perinatal outcomes of Southeast Asian (SEA) women compared with non-Hispanic white women in Washington. Using linked birth certificate and hospitalization discharge records for the years 1993-2006, we compared singleton births of Cambodian (3,858), Laotian (2,223), and Vietnamese (12,949) women with a random sample of white women (35,581). Associations between maternal nativity and perinatal outcomes were assessed using multivariable logistic regression. There are clear nativity differences among SEAs for gestational diabetes mellitus, anemia, placenta previa and febrile illness. SEAs had increased risks for these disorders when compared with white women. Compared with infants delivered of white women, infants of SEAs had increased risks for moderate to heavy meconium, birth injury and low birth weight. Differences in nativity among SEAs (populations that are traditionally studied in aggregate) should be considered when designing and carrying out interventions to prevent adverse pregnancy morbidity and outcomes among immigrants.

Placenta previa: neonatal death after live births in the United States

OBJECTIVE

The purpose of this study was to describe neonatal mortality rates among live births that were complicated by placenta previa in the United States.

STUDY DESIGN

This was a population-based retrospective cohort study of 1997 United States singleton live births. Neonatal deaths among pregnancies that were complicated by placenta previa were compared with deaths among pregnancies with no placenta previa. Adjusted and unadjusted hazard ratios were generated from a proportional hazards regression model.

RESULTS

Of 3,773,369 live births, 9656 were complicated by placenta previa (2.6 cases per 1000). Among cases of placenta previa, 114 neonatal deaths occurred (11.8 per 1000) versus 14951 (4 per 1000) among non-placenta previa neonates (P <.0001). The adjusted relative risk of death was three times higher among placenta previa neonates (hazard ratio, 3.06; 95% CI, 2.40-3.94). Placenta previa-related death was mediated through preterm delivery rather than small for gestational age.

CONCLUSION

Placenta previa triples the rate of neonatal mortality, which is mediated mainly through preterm birth.

Etiology and risk factors for placenta previa: an overview and meta-analysis of observational studies

OBJECTIVE

Several clinical and epidemiologic studies have reported disparate data on the prevalence rate as well as risk factors associated with placenta previa--a major cause of third-trimester bleeding. We performed a systematic literature review and identified 58 studies on placenta previa published between 1966 and 2000.

STUDY DESIGN

Each study was reviewed independently by the two authors and was scored (on the basis of established criteria) on method of diagnosis of placenta previa and on quality of study design. We extracted data on the prevalence rate of placenta previa, as well as associations with various risk factors from each study. A meta-analysis was then performed to determine the extent to which different risk factors predispose women to placenta previa.

RESULTS

Our results showed that the overall prevalence rate of placenta previa was 4.0 per 1000 births, with the rate being higher among cohort studies (4.6 per 1000 births), USA-based studies (4.5 per 1000 births) and hospital-based studies (4.4 per 1000 births) than among case-control studies (3.5 per 1000 births), foreign-based studies (3.7 per 1000 births) and population-based studies (3.7 per 1000 births), respectively. Advancing maternal age, multiparity, previous Cesarean delivery and abortion, smoking and cocaine use during pregnancy, and male fetuses all conferred increased risk for placenta previa. Strong heterogeneity in the associations between risk factors and placenta previa were noted by study design, accuracy in the diagnosis of placenta previa and population-based versus hospital-based studies.

CONCLUSION

Future etiological studies on placenta previa must, at the very least, adjust for potentially confounding effects of maternal age, parity, prior Cesarean delivery and abortions.

Previous cesarean section and abortion as risk factors for developing placenta previa

OBJECTIVE

To determine the risk of subsequent occurrence of placenta previa in women with a history of previous cesarean sections and/or spontaneous and induced abortions.

METHODS

A retrospective analysis of all single gestation deliveries at National University Hospital of Singapore from 1993-1997 was done. Women with placenta previa were identified by clinical or ultrasonographic diagnosis.

RESULTS

Of the 16,169 singleton deliveries, 164 women (1.0%) had placenta previa. Women with placenta previa had a significantly higher incidence of previous cesarean sections (p < 0.001). Among the 164 women with placenta previa, women with 1, 2, and 3 previous cesarean sections had 2.2 (95% CI 1.4, 3.4), 4.1 (95% CI 1.9, 8.8) and 22.4 (95% CI 6.4, 78.3) times increased risk of developing placenta previa respectively. Similarly, women with 2 or more previous abortions had a 2.1 (95% CI 1.2, 3.5) times increased risk of subsequently developing placenta previa.

CONCLUSION

There is a strong association between previous cesarean section and risk of subsequent development of placenta previa. This risk increased with the number of previous cesarean sections. Increasing frequency of abortions was also found to predispose a woman to placenta previa.