Changes in risk factors for preterm birth in Western Australia 1984-2006

Correlation Between Previous Caesarean Section and Adverse Maternal Outcomes Accordingly With Robson Classification: Systematic Review and Meta-Analysis

Background: The increasing rates of Caesarean section (CS) beyond the WHO standards (10–15%) pose a significant global health concern.

Objective: Systematic review and meta-analysis to identify an association between CS history and maternal adverse outcomes for the subsequent pregnancy and delivery among women classified in Robson classification (RC).

Search Strategy: PubMed/Medline, EbscoHost, ProQuest, Embase, Web of Science, BIOSIS, MEDLINE, and Russian Science Citation Index databases were searched from 2008 to 2018.

Selection Criteria: Based on Robson classification, studies reporting one or more of the 14 adverse maternal outcomes were considered eligible for this review.

Data Collection: Study design data, interventions used, CS history, and adverse maternal outcomes were extracted.

Main Results: From 4,084 studies, 28 (n = 1,524,695 women) met the inclusion criteria. RC group 5 showed the highest proportion among deliveries followed by RC10, RC7, and RC8 (67.71, 32.27, 0.02, and 0.001%). Among adverse maternal outcomes, hysterectomy had the highest association after preterm delivery OR = 3.39 (95% CI 1.56–7.36), followed by Severe Maternal Outcomes OR = 2.95 (95% CI 1.00–8.67). We identified over one and a half million pregnant women, of whom the majority were found to belong to RC group 5.

Conclusions: Previous CS was observed to be associated with adverse maternal outcomes for the subsequent pregnancies. CS rates need to be monitored given the prospective risks which may occur for maternal and child health in subsequent births.

How Does Preterm Delivery Contribute to the Increased Burden of Cardiovascular Disease? Quantifying the Economic Impact of Cardiovascular Disease in Women with a History of Preterm Delivery

Background: The association between preterm delivery (PTD) and maternal risk of cardiovascular disease (CVD) was demonstrated, but the economic burden of CVD in these women was unknown. Methods: A Markov microsimulation model, comprising no event, postacute coronary event (ACE, including acute myocardial infarction and unstable angina), poststroke, post-ACE and stroke, postheart failure, and death, was constructed to quantify the CVD burden in women with PTD from 2017 to 2066 using the Australian health care system perspective. Both first-ever and recurrent CVD events were accounted for in the model. Population with PTD histories was sourced from Australian Bureau of Statistics and costs of acute hospitalization and long-term management from government websites. Nonmonetary burden as years of life lost (YLL) was compared between women with and without PTD histories. Both dynamic (i.e., new cohort added every cycle) and static (i.e., population was stabilized) approaches were used to measure the CVD burden, with sensitivity analyses examining the robustness of results. Results: The dynamic model showed the total CVD burden caused by PTD as AUD11.4 billion for the next 50 years and the YLL as 0.34/capita, while the static model generated a cost of AUD4.5 billion and the YLL as 0.52/capita. Long-term management cost was the primary cost determinant (AUD9.4 billion and AUD3.7 billion, respectively) in the two models, with the results most sensitive to the discount rate and time horizon. Conclusions: Considering the substantial economic burden, recognizing PTD as a potential risk factor and encouraging women with PTD histories to participate in primary prevention programs would potentially curb the ever-increasing CVD burden.

Trends and predictors of extreme preterm birth: Western Australian population-based cohort study

Background

The preterm birth rate is rising in high-income countries and is associated with increased mortality and morbidity. Although the risks increase with greater prematurity and risk factors have been found to vary with gestational age and labour onset, few studies have focused on the myriad pathways to extreme preterm birth (20–27 weeks’ gestation). The current study investigated trends in extreme preterm birth by labour onset type and examined the antecedent risks to further our understanding around the identification of high-risk pregnancies.

Methods

Retrospective cohort study including all singleton extreme preterm births in Western Australia between 1986 and 2010. De-identified data from six core population health datasets were linked and used to ascertain extreme preterm births (excluding medical terminations and birth defects) after spontaneous onset of labour, preterm pre-labour rupture of membranes, and medically indicated labour onset. Trends over time in extreme preterm birth were analysed using linear regression. Multivariable regression techniques were used to assess the relative risks associated with each salient, independent risk factor and to calculate Population Attributable Risks (PARs).

Results

The extreme preterm birth rate including medical terminations and birth defects significantly increased over time whereas the extreme preterm birth rate excluding medical terminations and birth defects did not change. After medical terminations and birth defects were excluded, the rate of medically indicated extreme preterm births significantly increased over time whereas the rate of preterm pre-labour rupture of membranes extreme preterm births significantly reduced, and the rate of spontaneous extreme preterm births did not significantly change. In the multivariate analyses, factors associated with placental dysfunction accounted for >10% of the population attributable risk within each labour onset type.

Conclusions

First study to show that the increase in extreme preterm birth in high-income jurisdiction is no longer evident after medical terminations and birth defects are excluded. Interventions that identify and target women at risk of placental dysfunction presents the greatest opportunity to reduce extreme preterm births.

International variations in the gestational age distribution of births: an ecological study in 34 high-income countries

Background

Few studies have investigated international variations in the gestational age (GA) distribution of births. While preterm births (22-36 weeks GA) and early term births (37-38 weeks) are at greater risk of adverse health outcomes compared to full term births (39-40 weeks), it is not known if countries with high preterm birth rates also have high early term birth rates. We examined rate associations between preterm and early term births and mean term GA by mode of delivery onset.

Methods

We used routine aggregate data on the GA distribution of singleton live births from up to 34 high-income countries/regions in 1996, 2000, 2004, 2008 and 2010 to study preterm and early term births overall and by spontaneous or indicated onset. Pearson correlation coefficients were adjusted for clustering in time trend analyses.

Results

Preterm and early term births ranged from 4.1% to 8.2% (median 5.5%) and 15.6% to 30.8% (median 22.2%) of live births in 2010, respectively. Countries with higher preterm birth rates in 2004-2010 had higher early term birth rates (r > 0.50, P < 0.01) and changes over time were strongly correlated overall (adjusted-r = 0.55, P < 0.01) and by mode of onset.

Conclusion

Positive associations between preterm and early term birth rates suggest that common risk factors could underpin shifts in the GA distribution. Targeting modifiable population risk factors for delivery before 39 weeks GA may provide a useful preterm birth prevention paradigm.

Revisiting the Table 2 fallacy: A motivating example examining preeclampsia and preterm birth

BACKGROUND

A "Table Fallacy," as coined by Westreich and Greenland, reports multiple adjusted effect estimates from a single model. This practice, which remains common in published literature, can be problematic when different types of effect estimates are presented together in a single table. The purpose of this paper is to quantitatively illustrate this potential for misinterpretation with an example estimating the effects of preeclampsia on preterm birth.

METHODS

We analysed a retrospective population-based cohort of 2 963 888 singleton births in California between 2007 and 2012. We performed a modified Poisson regression to calculate the total effect of preeclampsia on the risk of PTB, adjusting for previous preterm birth. pregnancy alcohol abuse, maternal education, and maternal socio-demographic factors (Model 1). In subsequent models, we report the total effects of previous preterm birth, alcohol abuse, and education on the risk of PTB, comparing and contrasting the controlled direct effects, total effects, and confounded effect estimates, resulting from Model 1.

RESULTS

The effect estimate for previous preterm birth (a controlled direct effect in Model 1) increased 10% when estimated as a total effect. The risk ratio for alcohol abuse, biased due to an uncontrolled confounder in Model 1, was reduced by 23% when adjusted for drug abuse. The risk ratio for maternal education, solely a predictor of the outcome, was essentially unchanged.

CONCLUSIONS

Reporting multiple effect estimates from a single model may lead to misinterpretation and lack of reproducibility. This example highlights the need for careful consideration of the types of effects estimated in statistical models.

Caesarean section and risk of autism across gestational age: a multi-national cohort study of 5 million births

Background

The positive association between caesarean section (CS) and autism spectrum disorder (ASD) may be attributed to preterm delivery. However, due to lack of statistical power, no previous study thoroughly examined this association across gestational age. Moreover, most studies did not differentiate between emergency and planned CS.

Methods

Using population-based registries of four Nordic countries and Western Australia, our study population included 4 987 390 singletons surviving their first year of life, which included 671 646 CS deliveries and 31 073 ASD children. We used logistic regression to estimate odds ratios (OR) and their 95% confidence intervals (CI) for CS, adjusted for gestational age, site, maternal age and birth year. Stratified analyses were conducted by both gestational age subgroups and by week of gestation. We compared emergency versus planned CS to investigate their potential difference in the risk of ASD.

Results

Compared with vaginal delivery, the overall adjusted OR for ASD in CS delivery was 1.26 (95% CI 1.22-1.30). Stratified ORs were 1.25 (1.15-1.37), 1.16 (1.09-1.23), 1.34 (1.28-1.40) and 1.17 (1.04-1.30) for subgroups of gestational weeks 26-36, 37-38, 39-41 and 42-44, respectively. CS was significantly associated with risk of ASD for each week of gestation, from week 36 to 42, consistently across study sites (OR ranged 1.16-1.38). There was no statistically significant difference between emergency and planned CS in the risk of ASD.

Conclusion

Across the five countries, emergency or planned CS is consistently associated with a modest increased risk of ASD from gestational weeks 36 to 42 when compared with vaginal delivery.

The Relationships of Health Behaviour and Psychological Characteristics with Spontaneous Preterm Birth in Nulliparous Women

Objectives Preterm birth is the leading pregnancy outcome associated with perinatal morbidity and mortality and remains difficult to prevent. There is evidence that some modifiable maternal health characteristics may influence the risk of preterm birth. Our aim was to investigate the relationships of self-reported maternal health behaviour and psychological characteristics in nulliparous women with spontaneous preterm birth in prenatal primary care. Methods The data of our prospective study was obtained from the nationwide DELIVER multicentre cohort study (September 2009–March 2011), which was designed to examine perinatal primary care in the Netherlands. In our study, consisting of 2768 nulliparous women, we estimated the relationships of various self-reported health behaviours (smoking, alcohol consumption, folic acid supplementation, daily fruit, daily fresh vegetables, daily hot meal and daily breakfast consumption) and psychological characteristics (anxious/depressed mood and health control beliefs) with spontaneous preterm birth as a dichotomous outcome. Due to the clustering of clients within midwife practices, Generalized Estimating Equations was used for these analyses. Results Low health control beliefs was the sole characteristic significantly associated with spontaneous preterm birth (odds ratio 2.26; 95 % confidence interval 1.51, 3.39) after being adjusted for socio-demographics, anthropometrics and the remaining health behaviour and psychological characteristics. The other characteristics were not significantly associated with spontaneous preterm birth. Conclusions for Practice Maternal low health control beliefs need to be explored further as a possible marker for women at risk for preterm birth, and as a potentially modifiable characteristic to be used in interventions which are designed to reduce the risk of spontaneous preterm birth.

Risk of Mortality into Adulthood According to Gestational Age at Birth

OBJECTIVES

To quantify the independent risks of neonatal (0-28 days), postneonatal (29-364 days), 1- to 5- and 6- to 30-year mortality by gestational age and investigate changes in survival over time in an Australian birth cohort.

STUDY DESIGN

Maternal and birth related Western Australian population data (1980-2010) were linked to the state mortality data using a retrospective cohort study design involving 722 399 live-born singletons infants.

RESULTS

When compared with 39- to 41-week born infants, the adjusted risk ratio for neonatal mortality was 124.8 (95% CI 102.9-151.3) for 24-31 weeks of gestation, 3.4 (95% CI 2.4-4.7) for 35-36 weeks of gestation, and 1.4 (95% CI 1.1-1.8) for 37-38 weeks of gestation. For 24-31 weeks of gestation infants, the adjusted hazard ratio for postneonatal mortality (29-364 days) was 13.9 (95% CI 10.9-17.6), for 1- to 5-year mortality 1.4 (95% CI 0.7-3.0) and for 6- to 30-year mortality 1.3 (95% CI 0.8-2.3). The risk of neonatal and postneonatal mortality for those born preterm decreased over time.

CONCLUSIONS

In Western Australia, late preterm and early term infants experienced higher risk of neonatal and postneonatal mortality when compared with their full-term peers. There was insufficient evidence to show that gestational length was independently associated with mortality beyond 1 year of age. Neonatal and postneonatal mortality improved with each decade of the study period.

Maternal serum lead level during pregnancy is positively correlated with risk of preterm birth in a Chinese population

Lead (Pb) is a well-known developmental toxicant. The aim of the present study was to analyze the association between maternal serum Pb level and risk of preterm birth in a population-based birth cohort study. The present study analyzed a sub-study of the China-Anhui Birth Cohort that recruited 3125 eligible mother-and-singleton-offspring pairs. Maternal serum Pb level was measured by graphite furnace atomic absorption spectrometry. All subjects were classified into three groups by tertile division according to serum Pb level: Low-Pb (L-Pb, <1.18 μg/dl), Medium-Pb (M-Pb, 1.18-1.70 μg/dl), and High-Pb (H-Pb, ≥1.71 μg/dl). The rate of preterm birth was 2.8% among subjects with L-Pb, 6.1% among subjects with M-Pb, and 8.1% among subjects with H-Pb, respectively. After controlling confounding factors, the adjusted OR for preterm birth was 2.33 (95%CI: 1.49, 3.65) among subjects with M-Pb and 3.09 (95%CI: 2.01, 4.76) among subjects with H-Pb. Of interest, maternal Pb exposure in early gestational stage than in middle gestational stage was more susceptible to preterm birth. Moreover, maternal serum Pb level was only associated with increased risk of late preterm birth. The present study provides evidence that maternal serum Pb level during pregnancy is positively associated with risk of preterm birth in a Chinese population.

Comparison of early onset sepsis and community-acquired late onset sepsis in infants less than 3 months of age

Background

We compared demographic and clinical characteristics of early-onset sepsis (EOS) and community-acquired late onset sepsis (CA-LOS) in infants.

Methods

Our medical center is the sole hospital in southern-Israel, enabling incidence calculations. EOS (<7 days) and CA-LOS (7–90 days) episodes recorded between 2007 and 2013 were reviewed. Univariate and multivariate analyses were performed.

Results

70 EOS and 114 CA-LOS episodes were recorded. The respective mean ± SD annual rates per 1,000 live-births were 0.66 ± 0.16 and 1.03 ± 0.23. Prematurity (42.9 % vs. 17.0 %), premature rupture of membranes (PROM; 22.9 % vs. 1.9 %), leukopenia (29.0 % vs. 11.6 %), thrombocytopenia (44.9 % vs. 14.3 %) and Streptococcus agalactiae infections (22.7 % vs. 8.1 %) were more common in EOS. Fever (25.4 % vs. 79.1 %) and Streptococcus pneumoniae infections (1.3 % vs. 12.9 %) were less common in EOS. In both groups, Gram-negative bacteria predominated (~60 %). Longer hospitalization duration (23.3 ± 25.1 vs. 10.3 ± 8.6 days) and higher case fatality rate (20.0 % vs. 5.3 %) were noted in EOS. Antibiotic resistance rates to empiric EOS and CA-LOS treatments were 0.0 % and 1.2 %, respectively.

In multivariate analysis, adjusting for prematurity and ethnicity, PROM, central line, low Apgar-score, low birth-weight, ventilation support and non-vaginal delivery were risk factors for EOS. Normal temperature, thrombocytopenia and leukopenia characterized EOS.

Conclusion

EOS and CA-LOS rates were low in Jewish compared with Bedouin infants. EOS was characterized by higher rates of perinatal risk factors, S. agalactiae infections, normal temperature, thrombocytopenia, leukopenia and mortality, while fever and S. pneumoniae infections were common in CA-LOS. Current initial antibiotic regimens seem adequate, considering the susceptibility patterns of the isolated pathogens

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-016-0618-6) contains supplementary material, which is available to authorized users.

What contributes to disparities in the preterm birth rate in European countries?

PURPOSE OF REVIEW

In countries with comparable levels of development and healthcare systems, preterm birth rates vary markedly--a range from 5 to 10% among live births in Europe. This review seeks to identify the most likely sources of heterogeneity in preterm birth rates, which could explain differences between European countries.

RECENT FINDINGS

Multiple risk factors impact on preterm birth. Recent studies reported on measurement issues, population characteristics, reproductive health policies as well as medical practices, including those related to subfertility treatments and indicated deliveries, which affect preterm birth rates and trends in high-income countries. We showed wide variation in population characteristics, including multiple pregnancies, maternal age, BMI, smoking, and percentage of migrants in European countries.

SUMMARY

Many potentially modifiable population factors (BMI, smoking, and environmental exposures) as well as health system factors (practices related to indicated preterm deliveries) play a role in determining preterm birth risk. More knowledge about how these factors contribute to low and stable preterm birth rates in some countries is needed for shaping future policy. It is also important to clarify the potential contribution of artifactual differences owing to measurement.

Maternal characteristics and mid-pregnancy serum biomarkers as risk factors for subtypes of preterm birth

OBJECTIVE

To examine the relationship between maternal characteristics, serum biomarkers and preterm birth (PTB) by spontaneous and medically indicated subtypes.

DESIGN

Population-based cohort.

SETTING

California, United States of America.

POPULATION

From a total population of 1 004 039 live singleton births in 2009 and 2010, 841 665 pregnancies with linked birth certificate and hospital discharge records were included.

METHODS

Characteristics were compared for term and preterm deliveries by PTB subtype using logistic regression and odds ratios adjusted for maternal characteristics and obstetric factors present in final stepwise models and 95% confidence intervals. First-trimester and second-trimester serum marker levels were analysed in a subset of 125 202 pregnancies with available first-trimester and second-trimester serum biomarker results.

MAIN OUTCOME MEASURE

PTB by subtype.

RESULTS

In fully adjusted models, ten characteristics and three serum biomarkers were associated with increased risk in each PTB subtype (Black race/ethnicity, pre-existing hypertension with and without pre-eclampsia, gestational hypertension with pre-eclampsia, pre-existing diabetes, anaemia, previous PTB, one or two or more previous caesarean section(s), interpregnancy interval ≥ 60 months, low first-trimester pregnancy-associated plasma protein A, high second-trimester α-fetoprotein, and high second-trimester dimeric inhibin A). These risks occurred in 51.6-86.2% of all pregnancies ending in PTB depending on subtype. The highest risk observed was for medically indicated PTB <32 weeks in women with pre-existing hypertension and pre-eclampsia (adjusted odds ratio 89.7, 95% CI 27.3-111.2).

CONCLUSIONS

Our findings suggest a shared aetiology across PTB subtypes. These commonalities point to targets for further study and exploration of risk reduction strategies.

TWEETABLE ABSTRACT

Findings suggest a shared aetiology across preterm birth subtypes. Patterns may inform risk reduction efforts.

Associations of maternal atopic diseases with adverse pregnancy outcomes: a national cohort study

BACKGROUND

Maternal asthma has been associated with adverse pregnancy outcomes. Little is known about the influence of other atopic diseases on pregnancy outcomes. We assessed how various maternal atopic diseases might affect preterm birth, stillbirth, and neonatal death.

METHODS

By linking Norwegian national registries, we acquired information on maternal health, socio-demographic factors, pregnancy, birth, and neonatal outcome on all births in Norway from 1967 to 2003.

RESULTS

A total of 1 974 226 births were included. Of these, 1.8% had a record of maternal asthma, 3.4% of maternal atopic dermatitis, and 0.4% of maternal allergic rhinoconjunctivitis. Overall rates of preterm birth, stillbirth, and neonatal death were 6.0%, 0.6%, and 0.5%, respectively. After adjustments for possible confounders, maternal asthma was associated with increased risk of preterm birth (relative risk (RR), 1.15, [95% confidence interval (CI) 1.10, 1.21]). In contrast, maternal atopic dermatitis was associated with decreased risk of preterm birth (RR 0.90, [95% CI 0.86, 0.93]), stillbirth (RR 0.70, [95% CI 0.62, 0.79]), and neonatal death (RR 0.76, [95% CI 0.65, 0.90]). Similarly, maternal allergic rhinoconjunctivitis was associated with decreased risk of preterm birth (RR 0.84, [95% CI 0.76, 0.94]) and stillbirth (RR 0.40, [95% CI 0.25, 0.66]).

CONCLUSIONS

We confirmed the previously reported association of maternal asthma with increased risk for preterm birth. Unexpectedly, maternal atopic dermatitis and allergic rhinoconjunctivitis were associated with decreased risk of preterm birth and stillbirth. Mechanisms for these protective associations are unclear, and our findings require confirmation in further studies.