BMI mediates the association between low educational level and higher blood pressure during pregnancy in Japan

Mediating Factors in the Association of Maternal Educational Level With Pregnancy Outcomes: A Mendelian Randomization Study

Importance

Lower educational attainment is associated with increased risk of adverse pregnancy outcomes, but it is unclear which pathways mediate this association.

Objective

To investigate the association between educational attainment and pregnancy outcomes and the proportion of this association that is mediated through modifiable cardiometabolic risk factors.

Design, Setting, and Participants

In this 2-sample mendelian randomization (MR) cohort study, uncorrelated (R2 < 0.01) single-nucleotide variants (formerly single-nucleotide polymorphisms) associated with the exposure (P < 5 × 10-8) and mediators and genetic associations with the pregnancy outcomes from genome-wide association studies were extracted. All participants were of European ancestry and were largely from Finland, Iceland, the United Kingdom, or the US. The inverse variance-weighted method was used in the main analysis, and the weighted median, weighted mode, and MR Egger regression were used in sensitivity analyses. In mediation analyses, the direct effect of educational attainment estimated in multivariable MR was compared with the total effect estimated in the main univariable MR analysis. Data were extracted between December 1, 2022, and April 30, 2023.

Exposure

Genetically estimated educational attainment. The mediators considered were genetically estimated type 2 diabetes, body mass index, smoking, high-density lipoprotein cholesterol level, and systolic blood pressure.

Main Outcomes and Measures

Ectopic pregnancy, hyperemesis gravidarum, gestational diabetes, preeclampsia, preterm birth, and offspring birth weight.

Results

The analyses included 3 037 499 individuals with data on educational attainment, and those included in studies on pregnancy outcomes ranged from 141 014 for ectopic pregnancy to 270 002 with data on offspring birth weight. Each SD increase in genetically estimated educational attainment (ie, 3.4 years) was associated with an increased birth weight of 42 (95% CI, 28-56) g and an odds ratio ranging from 0.53 (95% CI, 0.46-0.60) for ectopic pregnancy to 0.81 (95% CI, 0.71-0.93) for preeclampsia. The combined proportion of the association that was mediated by the 5 cardiometabolic risk factors ranged from -17% (95% CI, -46% to 26%) for hyperemesis gravidarum to 78% (95% CI, 10%-208%) for preeclampsia. Sensitivity analyses accounting for pleiotropy were consistent with the main analyses.

Conclusions and Relevance

In this MR cohort study, intervening for type 2 diabetes, body mass index, smoking, high-density lipoprotein cholesterol level, and systolic blood pressure may lead to reductions in several adverse pregnancy outcomes associated with lower levels of education. Such public health interventions would serve to reduce health disparities attributable to social inequalities.

Secondhand smoke exposure is associated with the risk of hypertensive disorders of pregnancy: the Japan Environment and Children's Study

Hypertensive disorders of pregnancy (HDP) are associated with poor maternal and neonatal prognoses. Although several studies have indicated an effect of secondhand smoke (SHS) exposure on HDP, such evidence is lacking in Japan. Therefore, we analyzed data from the Japan Environment and Children's Study, a large-scale epidemiological investigation, to elucidate a possible link between SHS exposure and HDP risk. Data were obtained from the all-birth fixed datasets and included information on 104,062 fetuses and their parents. SHS exposure was assessed in terms of the frequency (rarely, 1-3, or 4-7 days/week) and the daily duration of exposure (<1, 1-2, or ≥2 h(s)/day). Modified Poisson regression model analyses were performed with adjustment for known risk factors for HDP. Additionally, the population attributable fractions (PAFs) of SHS exposure and maternal smoking to HDP prevalence were estimated. The relative risks of developing HDP among individuals with SHS exposures of 4-7 days/week and ≥2 h/day were 1.18 and 1.27 (95% confidence interval: 1.02-1.36 and 0.96-1.67), respectively, compared to the reference groups (rare exposure and <1 h/day). The PAFs for the risk of HDP due to SHS exposure and perinatal smoking were 3.8% and 1.8%, respectively. Japanese women with greater exposure to SHS have a higher risk of HDP after adjustment for possible confounding factors; thus, relevant measures are required to reduce SHS exposure to alleviate HDP risk. The association between second-hand smoking exposure and hypertensive disorders of pregnancy risk was analyzed using the JECS data. The relative risks in 4-7 days/week and ≥2 h/day of SHS exposures were 1.18 and 1.27, respectively. The PAFs due to SHS exposure and maternal smoking were 3.80% and 1.81%, respectively.

Effects of fine ambient particulate matters on de novo hypertensive disorders of pregnancy and blood pressure before 20 weeks

The effects of fine particulate matter (PM) on de novo hypertensive disorders of pregnancy (HDP) were inconsistent during the first and second trimesters. This study aimed to assess the trimester-specific effects of PM_2.5 and PM₁ prior to diagnosis of de novo HDP. The exposure of fine PM was predicted by satellite remote sensing data according to maternal residential addresses. De novo HDP was defined as gestational hypertension and preeclampsia during the current pregnancy. A logistic regression model was performed to assess the association of PM_2.5 and PM₁ with HDP during the first and early second trimesters (0-13 weeks and 14-20 weeks). The generalized estimating equation model was conducted to assess the effect of PM_2.5 and PM₁ on blood pressure. The present study included 22,821 pregnant women (mean age, 29.1 years) from 2013 to 2017. PM_2.5 and PM₁ were significantly associated with an increased risk of de novo HDP during the first trimester (OR = 1.070, 95% CI: 1.013-1.130; OR = 1.264, 95% CI: 1.058-1.511 for per 10 μg/m³) and early second trimester (OR = 1.045, 95% CI: 1.003-1.088; OR = 1.170, 95% CI: 1.002-1.366 for per 10 μg/m³). Significant trends of increased de novo HDP risk was also observed with the increment of PM (all P for trend <0.05). The stratified analyses demonstrated that the associations between exposure to fine PM and the risk of HDP were more pronounced among the pregnant women with maternal age above 35 and low maternal education level (all OR >1.047). Each 10 μg/m³ increase of PM₁ and PM_2.5 before diagnosis of de novo HDP elevated 0.204 (95% CI: 0.098-0.310) and 0.058 (95%CI: 0.033-0.083) mmHg of systolic blood pressure. Exposure to PM_2.5 and PM₁ during the first and early second trimester were positively associated with the risk of de novo HDP. The fine PM before diagnosis of de novo HDP elevated the systolic blood pressure.

Risk of De Novo Hypertensive Disorders of Pregnancy After Exposure to PM1 and PM2.5 During the Period From Preconception to Delivery: Birth Cohort Study

BACKGROUND

Particulate matter (PM) is detrimental to the respiratory and circulatory systems. However, no study has evaluated the lag effects of weekly exposure to fine PM during the period from preconception to delivery on the risk of hypertensive disorders of pregnancy (HDPs).

OBJECTIVE

We set out to investigate the lag effect windows of PM on the risk of HDPs on a weekly scale.

METHODS

Data from women with de novo HDPs and normotensive pregnant women who were part of the Peking University Retrospective Birth Cohort, based on the hospital information system of Tongzhou district, were obtained for this study. Meteorological data and data on exposure to fine PM were predicted by satellite remote sensing data based on maternal residential address. The de novo HDP group consisted of pregnant women who were diagnosed with gestational hypertension or preeclampsia. Fine PM was defined as PM2.5 and PM1. The gestational stage of participants was from preconception (starting 12 weeks before gestation) to delivery (before the 42nd gestational week). A distributed-lag nonlinear model (DLNM) was nested in a Cox regression model to evaluate the lag effects of weekly PM exposure on de novo HDP hazard by controlling the nonlinear relationship of exposure-reaction. Stratified analyses by employment status (employed or unemployed), education level (higher or lower), and parity (primiparity or multiparity) were performed.

RESULTS

A total of 22,570 pregnant women (mean age 29.1 years) for whom data were available between 2013 and 2017 were included in this study. The prevalence of de novo HDPs was 6.7% (1520/22,570). Our findings showed that PM1 and PM2.5 were significantly associated with an elevated hazard of HDPs. Exposure to PM1 during the 5th week before gestation to the 6th gestational week increased the hazard of HDPs. A significant lag effect of PM2.5 was observed from the 1st week before gestation to the 6th gestational week. The strongest lag effects of PM1 and PM2.5 on de novo HDPs were observed at week 2 and week 6 (hazard ratio [HR] 1.024, 95% CI 1.007-1.042; HR 1.007, 95% CI 1.000-1.015, respectively, per 10 μg/m3 increase). The stratified analyses indicated that pregnant women who were employed, had low education, and were primiparous were more vulnerable to PM exposure for de novo HDPs.

CONCLUSIONS

Exposure to PM1 and PM2.5 was associated with the risk of de novo HDPs. There were significant lag windows between the preconception period and the first trimester. Women who were employed, had low education, and were primiparous were more vulnerable to the effects of PM exposure; more attention should be paid to these groups for early prevention of de novo HDPs.

Smog and risk of maternal and fetal birth outcomes: A retrospective study in Baoding, China

Pregnant women are more susceptible to smog pollution than the general population. This study focused on the association between smog and birth outcomes, considering both pregnant mothers and their offspring. In this retrospective study, conducted in Baoding between 2013 and 2016, we enrolled 842 participants. Birth outcomes were low birth weight (LBW), pregnancy-induced hypertension (PIH), gestational diabetes mellitus (GDM), and premature rupture of membranes (PROM). The overall prevalence of LBW, PIH, GDM, and PROM was 8.2%, 14.8%, 16.5%, and 12.1%, respectively. Compared with lower pollution level, higher pollution level of fine particulate matter (particulate matter with aerodynamics diameter <2.5 μm) (PM2.5), inhalable particle (particulate matter with aerodynamics diameter <10 μm) (PM10), and CO increased the risk of term with LBW. PM2.5, PM10, and NO2 increased the risk of PIH during different trimesters, while PM10 increased the risk of PROM during trimester 3. In conclusion, smog significantly affects the risk of adverse birth outcomes by different exposure time windows.

Influence of Socio-Economic Factors and Region of Birth on the Risk of Preeclampsia in Sweden

Objectives: To investigate the association between socio-economic factors and the risk of preeclampsia in Sweden, specifically investigating if this relationship is confounded by maternal region of birth. Study design: All singleton births between 1999 and 2009 in an ethnically diverse area in southern Sweden, totaling 46,618 pregnancies, were included in this study. The data on maternal pregnancy outcomes were retrieved from a regional birth register and socio-economic variables from Statistics Sweden. The risk ratios for preeclampsia were calculated for educational level and household disposable income, adjusting for maternal region of birth, maternal age, body mass index, parity, and smoking. Results: Low income levels were associated with a higher risk for preeclampsia, adjusted risk ratio (aRR) = 1.25 (95% confidence interval [CI]: 0.99, 1.59) and aRR = 1.36 (95% CI: 1.10, 1.68) for the two lowest quintiles, respectively, compared to the highest. There was an educational gradient in preeclampsia risk, although not all categories reached statistical significance: aRR = 1.16, (95% CI: 0.89–1.50) for low educational attainment and aRR = 1.23 (95% CI: 1.08, 1.41) for intermediate educational attainment compared to women with highest education. The socio-economic gradient remained after adjusting for region of birth. There was a lower risk for preeclampsia for women born in Asia, aRR = 0.60 (95% CI: 0.47, 0.75), regardless of socio-economic position. Conclusion: An increased risk for preeclampsia was seen for women with measures of lower socio-economic position, even in a universal, government-funded healthcare setting. The relationship was not explained by region of birth, indicating that the excess risk is not due to ethnically differential genetic pre-disposition but rather due to modifiable factors.

Beta-2 receptor agonist exposure in the uterus associated with subsequent risk of childhood asthma

BACKGROUND

Although the beta-2 receptor agonist (B2RA) is occasionally prescribed in the prenatal period for women with preterm labor, few studies have referred to the long-term effects of intrauterine exposure to B2RA on fetus. We examined the association between intrauterine exposure to B2RA and asthma in the offspring.

METHODS

We obtained data from a hospital-based birth cohort study conducted in Tokyo, Japan. The outcomes of interest were three indicators, consisting of current wheeze, current asthma, and ever asthma at 5 years of age, based on the International Study of Asthma and Allergies in Childhood questionnaire. Logistic regression analysis was used to evaluate the association between intrauterine B2RA exposure and outcomes. To evaluate dose-dependent risk, we categorized children into three groups according to both the cumulative dose and duration (days) and conducted trend analysis.

RESULTS

Of 1158 children, 94 (8.1%) were exposed to B2RA in utero, and 191 (16.5%), 111 (9.6%), and 168 (14.5%) children experienced current wheeze, current asthma, and ever asthma, respectively. After adjusting for confounders, we found an increased risk of current asthma caused by B2RA exposure with an adjusted odds ratio of 2.04 (95% confidence interval: 1.02-4.05). Trend analysis showed that B2RA exposure in utero was associated with a dose-dependent increased risk of current asthma in terms of both cumulative dose and duration (P values for trend were .015 and .017, respectively). These results were similar to those for other outcome measures.

CONCLUSION

Exposure to B2RA in utero could be a risk for childhood asthma.

Timing of eczema onset and risk of food allergy at 3 years of age: A hospital-based prospective birth cohort study

BACKGROUND

Although recent studies suggest that eczema in early childhood is important in the development of food allergy, the importance of the timing of eczema onset has not been fully clarified.

OBJECTIVE

This study aim to identify an association between the timing of eczema onset and development of food allergy in a prospective birth cohort study.

METHODS

Data were obtained from the Tokyo Children's Health, Illness and Development (T-CHILD) study, which is a hospital-based birth cohort study currently in progress in Japan. A total of 1550 children were born to the recruited women. Outcome data for children were collected from questionnaires completed at 6 months, 1 and 3 years of age. Association between the timing of eczema onset and development of food allergy was estimated by logistic regression analyses. All analysis were performed using SPSS software with a two-sided 5% significance level.

RESULTS

Eczema in the first year of life was a significant risk factor in multivariate analysis (aOR 3.90, 95% CI 2.34-6.52, p<0.001). In each age (by month) stratum, infants with onset of eczema within the first 1-2 months after birth had the highest risk of food allergy at 3 years of age (aOR 6.61, 95% CI 3.27-13.34, p<0.001).

CONCLUSION

Infants with early eczema onset (especially within the first 1-4 months after birth) were found to have an increased risk of developing food allergy at 3 years of age. Our findings may contribute to a better understanding of the timing of eczema onset as a potentially modifiable risk factor and to defining those who may need to be on guard for food allergy.

Preconceptional exposure to oral contraceptive pills and the risk of wheeze, asthma and rhinitis in children

BACKGROUND

The prevalence of maternal oral contraceptive pills (OCP) use and that of childhood asthma are high in western countries. The aim of this study is to examine the association of OCP use with childhood wheeze and allergic diseases in Japan.

METHODS

Relevant data were extracted from a hospital based birth cohort study named as Tokyo-Children's Health, Illness and Development Study (T-CHILD) of which questionnaire conducted during pregnancy included maternal history and duration of OCP use. To identify wheeze and allergic diseases in the children, the questionnaire of the International Study of Asthma and Allergies in Childhood (ISAAC) was used. Logistic regression models were applied to estimate those association and adjustments were made for maternal history of allergy, maternal education level, maternal age at pregnancy, maternal BMI, maternal smoking during pregnancy, mode of delivery, gestational age at delivery, daycare attendance, number of previous live births, and gender of child.

RESULTS

OCP use was associated with ever wheeze (adjusted odds ratio [aOR], 1.62; 95% confidence interval [CI], 1.10-2.40), current wheeze (aOR, 1.59; 95% CI, 1.01-2.50), ever asthma (aOR, 1.65; 95% CI, 1.02-2.65), and ever rhinitis (aOR, 1.90; 95% CI, 1.30-2.80). Compared with no prior OCP use, using OCP for more than three months statistically increased the odds of ever wheeze (P = 0.012), current wheeze (P = 0.035), and ever rhinitis (P = 0.002).

CONCLUSIONS

Our findings suggest that maternal OCP use has a role in the development of wheeze, asthma and rhinitis in children. Extended use of OCP is likely to increase the risk of wheeze and rhinitis.

Knowledge of midwives about hypertensive disorders during pregnancy in primary healthcare

BACKGROUND

Many factors or medical conditions may influence the outcome of pregnancy,which in turn, may increase infant and maternal morbidity and mortality. One such condition is an increase in blood pressure (BP).

SETTING

The study was conducted in maternity obstetrical units (MOUs) in primary healthcare clinics (PHCs) in the Eastern Cape, South Africa.

OBJECTIVES

To determine the knowledge about hypertensive disorders during pregnancy (HDPs) of registered midwives working in MOUs in PHCs.

METHODS

A quantitative descriptive correlation research design was applied. A simple random sample of 43 (44%) rural and urban clinics was selected, and all registered midwives (n = 101) working in these clinics completed a self-administered questionnaire. Data were collected over a period of 1 month. The reliability and validity of the methodology were supported by experts and a pilot study. Descriptive statistics including various statistical tests to determine any associations between variables using a 95% confidence interval were applied.

RESULTS

A gap in the knowledge of midwives about HDPs was identified. Only 56.4% of the participants correctly answered the questions on the clinical manifestations of severe pre-eclampsia and 68.3% on the factors affecting BP, whereas 27.7% had no understanding about pre-eclampsia. Significant statistical differences were identified in the knowledge of staff in clinics where doctors visit regularly versus those in clinics where there are no visits (p = 0.04), and between experience of midwives and management of HDPs (p = 0.02).

CONCLUSION

The knowledge of midwives is deficient regarding HDPs. Continuous professional development is critical in midwifery both in theory and in clinical practice.

Labor force participation and secondary education of gender inequality index (GII) associated with healthy life expectancy (HLE) at birth

BACKGROUND

What is the factor that affects healthy life expectancy? Healthy life expectancy (HLE) at birth may be influenced by components of the gender inequality index (GII). Notably, this claim is not tested on the between components of the GII, such as population at least secondary education (PLSE) with ages 25 and older, labor force participation rate (LFPR) with ages 15 and older, and the HLE in the world's countries. Thus, this study estimates the associations between the PLSE, LFPR of components of the GII and the HLE.

METHODS

The data for the analysis of HLE in 148 countries were obtained from the World Health Organization. Information regarding the GII indicators for this study was obtained from the United Nations database. Associations between these factors and HLE were assessed using Pearson correlation coefficients and regression models.

RESULTS

Although significant negative correlations were found between HLE and the LFPR, positive correlations were found between HLE and PLSE. Finally, the HLE predictors were used to form a model of the components of the GII, with higher PLSE as secondary education and lower LFPR as labor force (R(2) = 0.552, P <0.001).

CONCLUSIONS

Gender inequality of the attainment secondary education and labor force participation seems to have an important latent effect on healthy life expectancy at birth. Therefore, in populations with high HLE, the gender inequalities in HLE are smaller because of a combination of a larger secondary education advantage and a smaller labor force disadvantage in male-females.

Socioeconomic status and the risk of suspected autism spectrum disorders among 18-month-old toddlers in Japan: a population-based study

The association between family socioeconomic status (SES) and the suspected autism spectrum disorder (ASD) status of 18-month-old toddlers was investigated using a population-based sample in Japan, which has a universal healthcare system and a mandatory health checkup system for toddlers. Questionnaires including SES measurements and modified checklist for autism in toddlers were mailed to all families with 18-month-old toddlers in Chiba, a city near Tokyo (N = 6,061; response rate: 64%). The results of logistic regression analysis (which were adjusted for potential confounders) indicated that low maternal education, but not paternal education or family income, were associated with having suspected ASD offspring. Lower maternal education was associated with an increased risk of autistic traits in Japan.