Marital status and cohabitation during pregnancy: relationship with social conditions, antenatal care and pregnancy outcome in France

Gestational exposure to organochlorine compounds and metals and infant birth weight: effect modification by maternal hardships

BACKGROUND

Gestational exposure to toxic environmental chemicals and maternal social hardships are individually associated with impaired fetal growth, but it is unclear whether the effects of environmental chemical exposure on infant birth weight are modified by maternal hardships.

METHODS

We used data from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study, a pan-Canadian cohort of 1982 pregnant females enrolled between 2008 and 2011. We quantified eleven environmental chemical concentrations from two chemical classes - six organochlorine compounds (OCs) and five metals - that were detected in ≥ 70% of blood samples collected during the first trimester. We examined fetal growth using birth weight adjusted for gestational age and assessed nine maternal hardships by questionnaire. Each maternal hardship variable was dichotomized to indicate whether the females experienced the hardship. In our analysis, we used elastic net to select the environmental chemicals, maternal hardships, and 2-way interactions between maternal hardships and environmental chemicals that were most predictive of birth weight. Next, we obtained effect estimates using multiple linear regression, and plotted the relationships by hardship status for visual interpretation.

RESULTS

Elastic net selected trans-nonachlor, lead, low educational status, racially minoritized background, and low supplemental folic acid intake. All were inversely associated with birth weight. Elastic net also selected interaction terms. Among those with increasing environmental chemical exposures and reported hardships, we observed stronger negative associations and a few positive associations. For example, every two-fold increase in lead concentrations was more strongly associated with reduced infant birth weight among participants with low educational status (β = -100 g (g); 95% confidence interval (CI): -215, 16), than those with higher educational status (β = -34 g; 95% CI: -63, -3). In contrast, every two-fold increase in mercury concentrations was associated with slightly higher birth weight among participants with low educational status (β = 23 g; 95% CI: -25, 71) compared to those with higher educational status (β = -9 g; 95% CI: -24, 6).

CONCLUSIONS

Our findings suggest that maternal hardships can modify the associations of gestational exposure to some OCs and metals with infant birth weight.

Risk factors for preterm labor: An Umbrella Review of meta-analyses of observational studies

Preterm birth defined as delivery before 37 gestational weeks, is a leading cause of neonatal and infant morbidity and mortality. Understanding its multifactorial nature may improve prediction, prevention and the clinical management. We performed an umbrella review to summarize the evidence from meta-analyses of observational studies on risks factors associated with PTB, evaluate whether there are indications of biases in this literature and identify which of the previously reported associations are supported by robust evidence. We included 1511 primary studies providing data on 170 associations, covering a wide range of comorbid diseases, obstetric and medical history, drugs, exposure to environmental agents, infections and vaccines. Only seven risk factors provided robust evidence. The results from synthesis of observational studies suggests that sleep quality and mental health, risk factors with robust evidence should be routinely screened in clinical practice, should be tested in large randomized trial. Identification of risk factors with robust evidence will promote the development and training of prediction models that could improve public health, in a way that offers new perspectives in health professionals.

Trends in Tobacco Smoking in Pregnant Women: Data From French National Perinatal Surveys

Objectives: To describe maternal smoking trends in France between 1972 and 2016, and identify whether maternal characteristics associated with smoking in the 3rd trimester of pregnancy evolved between 2010 and 2016. Methods: Using French National Perinatal Surveys, we estimated proportions of smokers and the number of cigarettes smoked both just before pregnancy and during the 3rd trimester from 1972 to 2016. We used a Poisson model with robust variance to estimate prevalence ratios for smoking during pregnancy. Results: Proportions of mothers quitting smoking were relatively stable (46.0% in 1972 and 45.8% in 2016). The number of cigarettes smoked just before pregnancy and in the 3rd trimester decreased from 1995 onward. However, proportions of smokers remained high before (30.1%) and during the 3rd trimester in 2016 (16.2%). Smoking in the 3rd trimester was associated with a lower education level and lower income in both 2010 and 2016, whereas the association with age, country of birth and parity varied according to the survey year. Conclusion: Early targeted interventions are needed for smokers who plan to have a child and must take smokers' characteristics during pregnancy into account.

Got daddy issues? Fathers impact on perinatal outcomes

Mothers' genetics as well as their environment, behaviors, and social determinants of health are all important factors influencing short and long term childhood outcomes. There is an emerging body of literature investigating the extent to which fathers also contribute to their offspring's future health. We review fathers' impact on short term birth outcomes, longer term health, and neurodevelopment to emphasize the inter-relatedness of individual paternal traits. Factors that are linked to offspring outcomes include paternal demographics, race, stress, marriage and support, mental health, and the baseline health and behaviors of fathers. Several methodologic issues exist in current research such as maternal report of paternal information. Mechanisms proposed regarding paternal effect on progeny health range from genetic to reduction of stress of mothers through support. These are varied, possibly inter-related, and difficult to isolate as a single etiology. Future initiatives need to support fathers to allow them to support their families.

The Effect of Prenatal Stress, Proxied by Marital and Paternity Status, on the Risk of Preterm Birth

Uncertainty and insecurity in the relationship between the mother and father of a child are responsible for heightened maternal stress, which can lead to preterm birth (PTB). Different intensities of prenatal stress (proxied by four levels of marital status linked with the presence or absence of paternal data on birth records) were defined as the Marital-Father Data index. We assessed the impact of those varying intensities of prenatal stress on PTB with respect to parity among a group of Polish mothers residing in Krakow (N = 87,916). We found a pattern across the adjusted risk ratios (RR) of preterm birth that ordered these estimates in an increasing trend towards higher risk, beginning with the group of married mothers with father data present (baseline), through the groups of legitimizing marriages—married after conception with father data present (RR = 1.1; 95% Confidence Intervals (CI) 1.0–1.2) and unmarried mothers with father data present (RR = 1.3; 95% CI 1.2–1.5) to the group of unmarried mothers with father data absent (RR = 1.9; 95% CI 1.7–2.2). The adjusted p for the linear trend between Marital-Father Data index and PTB was less than 0.001. The adjusted effect of perceived prenatal stress differed with respect to parity (confirmed by statistically significant interactions between Marital-Father Data index levels and parity), with a higher magnitude of this effect noted among multiparous versus primiparous women. Low paternal involvement and support during pregnancy may negatively affect PTB risk and this effect may differ in relation to parity status. More attention should be paid to maternal pregnancy stress, especially of multiparous mothers, to decrease the risk of unfavorable birth outcomes.

Do preterm infants with a birth weight ≤1250 g born to single-parent families have poorer neurodevelopmental outcomes at age 3 than those born to two-parent families?

OBJECTIVE

Investigate neurodevelopmental outcomes at 3 years corrected age in infants with a birth weight ≤1250 g born to single parents.

STUDY DESIGN

Infants born between 1995 and 2010 with a birth weight ≤1250 g were considered eligible. Primary outcome was neurodevelopmental impairment; considered present if a child had any of the following: cerebral palsy, cognitive delay, visual impairment, or deafness/neurosensory hearing impairment. Univariate and multivariate analyses were performed.

RESULT

A total of 1900 infants were eligible for inclusion. Follow-up data were available for 1395; 88 were born to a single parent. Infants in the single-parent group had higher mortality (18% vs. 11%, p = 0.009), IQ ≥1 SD below the mean (40% vs. 21%, p = 0.001) and any neurodevelopmental impairment (47% vs. 29%, p = 0.003). Single-parent family status, maternal education, bronchopulmonary dysplasia and severe neurological injury were significant predictors of intellectual impairment at 3 years corrected age.

CONCLUSION

Preterm infants with a birth weight ≤1250 g born to single parents at birth have poorer intellectual functioning at 3 years corrected age.

Life course variation in the relation between maternal marital status and preterm birth

PURPOSE

Maternal marriage is protective against preterm birth (PTB), whereas advanced maternal age is associated with increased PTB risk. Because relations between social factors and health may vary during the life course, we assessed how the relation between marital status and PTB risk may change with maternal age.

METHODS

We assessed the interaction between marital status and maternal age as a determinant of PTB among all live singleton births in Michigan between 1995 and 2006. We also fit stratified models by race. We calculated absolute differences in predicted PTB as well as odds ratios of PTB by marital status for each age group.

RESULTS

In adjusted models, there was a significant interaction (p(interaction)<.001) between marital status and maternal age. The predicted probability of PTB by marital status was marginally different among mothers ages 20-25 years (absolute difference of 1.5%); this difference was substantially greater (3.9% or greater) after 31 years of age. Odds of PTB followed a similar trajectory. Findings were similar among black and white mothers.

CONCLUSIONS

The relationship between marriage and PTB may vary with maternal age suggesting that the influence of social factors on risk for adverse birth outcomes may differ through the maternal life trajectory. We discuss plausible explanations for these findings.

Maternal marital status and birth outcomes: a systematic review and meta-analyses

Systematically review risks of an infant being born with low birth weight (LBW), preterm birth (PTB) or small for gestational age (SGA) among married and unmarried women. Medline, Embase, CINAHL, and bibliographies of identified articles were searched for English language studies. Studies reporting birth outcomes of married and unmarried (single and cohabitant) were included. Two reviewers independently collected data and assessed the quality of the studies for biases in sample selection, exposure assessment, confounder, analytical, outcome assessments, and attrition. Meta-analyses were performed using random effect model for both unadjusted and adjusted data and odds ratio (OR), and 95% confidence interval (CI) were calculated. Twenty-one studies of low to moderate risk of bias were included. Compared to married mothers unadjusted odds of (a) LBW was increased among unmarried (OR 1.46, 95%CI 1.25-1.71), single (OR 1.65, 95%CI 1.44-1.88) and cohabitating (OR 1.29, 95%CI 1.25-1.32) mothers; (b) PTB was increased among unmarried (OR 1.22, 95%CI 1.14-1.31), single (OR 1.54, 95%CI 1.39-1.72) and cohabitating (OR 1.15, 95%CI 1.08-1.23) mothers and (c) SGA birth was increased among unmarried (OR 1.45, 95%CI 1.32-1.61), single (OR 1.70, 95%CI 1.47-1.97) and cohabitating (OR 1.36, 95%CI 1.30-1.42) mothers. Meta-analyses of adjusted odds estimates confirmed these findings at marginally lower odds. Maternal unmarried status is associated with an increased risk of LBW, PTB and SGA births.

Primary predictors of preterm labour

Spontaneous preterm birth accounts for 60% of all preterm births in developed countries. With the increase in multiple pregnancies, induced preterm birth and the progress in neonatal care for extremely preterm neonates, spontaneous preterm birth for singleton pregnancies in developed countries has probably decreased over the past 30 years. This decrease is likely to be related to better prenatal care for all pregnant women because the recognition of primary risk factors in early or late pregnancy remains a basic part of prenatal care. The failure to distinguish between induced and spontaneous preterm labour in most population-based studies makes it difficult to interpret results with respect to the primary predictors of preterm labour. Many such primary predictors of preterm labour have been used over the past 20-30 years. These include individual factors, socio-economic factors, working conditions and obstetric and gynaecological history. Risk scores have been proposed in order to produce these data. Unfortunately, the predictive value of these scores, especially their specificity, is poor, mainly because all of these factors are indirect. We still cannot identify the mechanisms that lead to preterm labour and birth. New markers more directly related to preterm labour have recently been proposed, some of which relate to direct causes of preterm labour such as cervical ultrasound measurement, fetal fibronectin (FFN), salivary estriol, serum CRH and bacterial vaginosis. Several of these have predictive values, which are potentially useful for clinical practice. Nonetheless, pregnant women in developed countries are already closely monitored throughout pregnancy. Before proposing new screening tests to be applied systematically to all pregnant women, their advantages and drawbacks must be fully evaluated.

Marital status, cohabitation, and risk of preterm birth in Europe: where births outside marriage are common and uncommon

This article explores whether the impact of marital status on the risk of preterm birth varies in relation to marital practices in the population, defined by the proportion of out-of-marriage births. Data come from a case-control study of the determinants of preterm birth in 16 European countries (5456 cases and 8234 controls). There is a significantly elevated risk of preterm birth associated with both cohabitation (OR = 1.29 [1.08, 1.55]) and single motherhood (OR = 1.61 [1.26, 2.07]) for women living in countries where fewer than 20 of births occur outside marriage. In contrast, there is no excess risk associated with marital status when out-of-marriage births are more common. This overall result does not apply to all subgroups of preterm births: different patterns emerge for early preterm births and preterm births induced for medical reasons. It is important to consider social context in the analysis of individual risk factors.

[Socio-economic factors associated with preterm delivery. Results of the European project in Spain]

OBJECTIVES

The objectives of this paper were to analyse the effect of social, personal and medical risk factors on preterm birth (moderate versus very preterm) or on two preterm birth groups (spontaneous versus indicated).

METHODS

Results from the Spanish collaborating centre of the European multicentre case-control study EUROPOP (European Program of Occupational Risks and Pregnancy Outcome) are presented. All preterm births (529) between 22 and 36 completed weeks of amenorrhea and 788 births of 37 or more completed weeks of amenorrhea (control group) are included. Explicative variables are divided in social, personal and medical factors. A univariate and multivariate analysis by means of a logistic regression were carried out.

RESULTS

Very preterm birth risk was higher for women over 34 years, adjusted OR: 2.53 (1.42-4.52), with lower educational level, adjusted OR: 1.79 (1.07-2.98), for primigravid women or multigravid women with only first trimestre abortion, adjusted OR: 1.86 (1.13-3.04), and for multigravid women with previous preterm birth or second trimestre abortion, adjusted OR: 5.53 (2.97-10.35). A similar trend was observed for moderate preterm birth. Probability of spontaneous preterm birth was higher for mother over 34 years, adjusted OR: 1.51 (1.01-2.26), with lower income, adjusted OR: 1.75 (1.07-2.88) and for multigravid women with previous preterm birth or second trimestre abortion, adjusted OR: 2.96 (1.86-4.71). Results were similar for indicated preterm birth.

CONCLUSION

Social differences were found to be related to moderate and very preterm birth. No differences were observed between risk factors and kind of preterm birth: spontaneous or indicated.

First report from the Plunket National Child Health Study: smoking during pregnancy in New Zealand

The Plunket National Child Health Study is a 5-year longitudinal study of a birth cohort of 4285 children born in New Zealand during 1990-1991. This paper describes the major lines of epidemiological research, the methods and study design, and reports on the demographic data of New Zealand children. During this first report from the Plunket Child Health Study, we examine on the smoking rates of New Zealand mothers during pregnancy. Overall 33% of mothers smoked during pregnancy. Particularly high rates were found amongst teenage mothers,. Maori women, single women and women with lower educational levels. Over 60% of women in these categories smoked during pregnancy.

An indicator of adverse pregnancy outcome in France: not receiving maternity benefits

STUDY OBJECTIVE

The aim was to compare the social characteristics, the pregnancy outcome, and the antenatal care of women in France who did not receive maternity benefits to women who did. These benefits (860 FF, approx 86 pounds per month) are given to every pregnant woman, starting in the second trimester. Payments are made on the condition that at least three antenatal visits are made, the first being before the end of the first trimester.

DESIGN

The study involved a random sample of women who were interviewed after delivery during their stay in hospital. Data on pregnancy outcome were collected from medical records.

SETTING

The study was carried out in four public maternity units in different regions of France.

PARTICIPANTS

1692 women were included in the analysis (86.8% of the selected sample). Of 257 exclusions, 40 had multiple pregnancies, 189 had missing data, and 28 did not answer the question concerning maternity benefits.

MEASUREMENTS AND MAIN RESULTS

4.3% of the women did not receive any maternity benefits. These women lived in poorer social conditions than the women who received the benefits. They had a higher preterm delivery rate, after controlling for risk factors in a logistic regression. Women without maternity benefits were characterised by a lower level of care, yet the majority began their antenatal care during the first trimester or had more than six visits.

CONCLUSIONS

Not receiving maternity benefits during pregnancy is an index of an underprivileged situation and a risk factor for pregnancy outcome.

Antenatal care received and its association with preterm birth in Greece

A total population sample of singleton births to mothers with certain dates of last menstrual period (LMP) was identified from the Greek National Perinatal Survey of April 1983. Two groups of mothers were considered separately, 3116 primigravidae and 6524 multigravidae, with preterm birth rates of 5.9% and 8.4% respectively. Of all the antenatal care factors tested, primigravidae showed significant associations (unadjusted) with haematocrit level and with drugs taken during pregnancy. The logistic regression analysis which followed showed that the only factor independently associated with preterm delivery for that group of mothers was drugs taken during this period: women taking no drugs (including vitamins and iron) had the highest risk of preterm delivery. In contrast, multigravidae showed significant unadjusted associations with a great variety of parameters of antenatal care. Nevertheless, in the logistic regression analysis only three proved to have independent significant associations: drugs taken during pregnancy (reduced risk among mothers taking vitamins and iron), hospital admission during pregnancy (mainly for cervical cerclage) and the pattern of antenatal care during the first two trimesters (those attending the recommended number of times having least risk).

Socio-economic factors associated with preterm delivery in Greece: a population-based study

A total population sample of singleton births to mothers with certain last menstrual period dates was identified from the Greek National Perinatal Survey of April 1983. Two groups were considered (3116 primigravidae and 6524 multigravidae) with preterm rates of 5.9% and 8.4% respectively. Of all 17 factors considered, primigravidae showed unadjusted significant associations between preterm delivery and marital status, region of mother's residence, maternal occupation, maternal education and paternal education level. Multigravidae preterm deliveries were associated with marital status, mother's age at marriage, father's age at marriage, mother's age at delivery, mother's education, father's education and maternal smoking at the end of the pregnancy. Logistic regression was used to identify the socio-economic and demographic characteristics independently associated with preterm delivery. For primigravidae, the only significant factors were maternal marital status and region of the country. For multigravidae, significant factors were maternal age at delivery, marital status and smoking habit at the end of pregnancy.

Prediction of preterm delivery: is it substantially improved by routine vaginal examinations?

The ability of routine vaginal examinations to improve the prediction of preterm delivery was assessed in a group of 6909 women who were registered at each prenatal visit and on whom this examination had been carried out. We compared two risk scores, one including known risk factors (maternal characteristics and symptoms reported by women), and the other including these factors and the findings of vaginal examination. These risk scores were computed by multiplying the adjusted odds ratio estimations obtained by logistic regressions. The prediction of preterm delivery was improved significantly by vaginal examination at 25 to 28 weeks' and 29 to 31 weeks' gestation. However, the improvement was not very large: when 30% of nulliparous women were classified as high risk at 29 to 31 weeks, the sensitivity was 55% when considering only the risk factors and 63% when adding the findings of vaginal examination; the percentages were 52% and 55%, respectively, for parous women. These results partially explain why the medical practice of routine vaginal examinations varies from country to country.

Low birth-weight and pre-term delivery in South-east Asia. The WHO International Collaborative Study of Hypertensive Disorders of Pregnancy

Population-based data from 10 centres in Burma, Thailand, China and Vietnam, have been analysed to assess those social and environmental factors which may be associated with pre-term delivery and low birth-weight. The philosophy behind the study was that if the same association was found in different countries, then the association may be causal; if associations differed in the various countries, then causality was unlikely. The major findings were as follows: a strong association between low birth-weight and pre-term delivery and the unmarried state (RR 1.64, 1.39), a consistent reduced risk of pre-term delivery when the father was in a managerial post (RR 0.77), an excess risk of pre-term delivery if the mother was a housewife (RR 1.16), lifting heavy objects at the time of quickening (RR 1.63) or frequently bending and stooping at the time of quickening (1.15). Strong associations were found with both paternal and maternal education levels but these were strongest for the mother's education level. The association was far stronger for pre-term delivery than for low birth-weight and it is assumed that the low birth-weight effect is secondary to pre-term delivery. The only variation with maternal age concerned an excess of low birth-weight among teenage mothers, but not of pre-term delivery, and an excess of low birth-weight but not pre-term delivery among mothers with small head circumferences or small arm circumferences. We conclude that the aetiology of growth retardation and pre-term delivery are probably different in South-east Asia, and point out the need to elucidate further the strong variation with education level.