Interpregnancy change in smoking habits and risk of preeclampsia: a population-based study

Maternal Smoking and Risk of Hypertensive Disorders of Pregnancy: Effect Modification by Body Mass Index and Gestational Weight Gain

BACKGROUND

Although smoking cigarettes has been shown to have a protective effect on preeclampsia, quitting smoking also results in weight gain. Weight gain leading to an obese body mass index is a risk factor for hypertensive disorders of pregnancy (HDP).

METHODS

The objective of this study was to explore the relationship between smoking status, body mass index, and gestational weight gain on the risk of HDP. A cross-sectional analysis was performed utilizing US birth certificate data. We examined HDP risks in relation to maternal smoking, body mass index, and gestational weight gain. Associations were expressed as rate ratios with 95% CIs and adjusted for potential confounders. Clinically important outcomes of smoking throughout pregnancy were also evaluated.

RESULTS

Of the 22 191 568 women studied, HDP rates among nonsmokers, those who quit smoking, and persistent smokers were 6.8%, 8.6%, and 7.0%, respectively. The rate ratio of HDP was higher for women who quit smoking, especially evident among those with excessive gestational weight gain. Corrections for exposure misclassification and unmeasured confounding strengthened the associations among women who quit smoking. There was an almost 6-fold increase in the rate of stillbirth for persistent smokers (2.3%) compared with those who quit smoking (0.4%) and nonsmokers (0.4%).

CONCLUSIONS

Women who quit smoking during pregnancy were more likely to gain excessive weight and develop HDP. Although quitting smoking during pregnancy may be associated with an increase in the risk of HDP, it is also associated with a reduced risk of stillbirth. Pregnant women counseled to quit smoking should also receive counseling on nutrition and exercise to prevent excessive gestational weight gain.

The association between diet quality index-international and dietary diversity score with preeclampsia: a case-control study

BACKGROUND

Preeclampsia is a significant complication that occurs during the second half of pregnancy. Recent studies have indicated that dietary factors play a crucial role in the development of preeclampsia. The Diet Quality Index-International (DQI-I) and Dietary Diversity Score (DDS) are appropriate indices for assessing the quality of foods, meals, and diets. This study aimed to investigate the relationship between DQI-I, DDS, and preeclampsia.

METHODS

This study utilized a case-control design. A total of 90 newly diagnosed preeclampsia cases and 90 healthy controls were included from a referral hospital in Tabriz, Iran. DQI-I and DDS were calculated based on information obtained from a reliable Food Frequency Questionnaire consisting of 168 food items, which assessed participants' usual diet. Logistic regression analysis adjusted for age, body mass index, education, family history of preeclampsia, and total energy intake was used to estimate odds ratios (ORs).

RESULTS

The mean age and pre-pregnancy body mass index of the participants were: 27.14 ± 4.40 years and 26.09 ± 3.33 kg/m2, respectively. After adjusting for various confounders, we found significant inverse association between the risk of developing preeclampsia and both DQI-I and DDS. The highest quartile of DQI-I had a significantly lower risk of developing preeclampsia compared to the first quartile (OR = 0.02, 95% CI [0.005, 0.08]) (P < 0.001). Similarly, the highest quartile of DDS had a significantly lower risk of developing preeclampsia compared to the first quartile (OR = 0.09, 95% CI [0.03, 0.31]) (P = 0.001).

CONCLUSIONS

Our findings suggest that maintaining a high-quality and diverse diet is associated with a lower risk of preeclampsia. Further studies are needed to confirm these associations and explore potential causal relationships.

Short interpregnancy interval and pregnancy outcomes: How important is the timing of confounding variable ascertainment?

BACKGROUND

Estimation of causal effects of short interpregnancy interval on pregnancy outcomes may be confounded by time-varying factors. These confounders should be ascertained at or before delivery of the first ("index") pregnancy, but are often only measured at the subsequent pregnancy.

OBJECTIVES

To quantify bias induced by adjusting for time-varying confounders ascertained at the subsequent (rather than the index) pregnancy in estimated effects of short interpregnancy interval on pregnancy outcomes.

METHODS

We analysed linked records for births in British Columbia, Canada, 2004-2014, to women with ≥2 singleton pregnancies (n = 121 151). We used log binomial regression to compare short (<6, 6-11, 12-17 months) to 18-23-month reference intervals for 5 outcomes: perinatal mortality (stillbirth and neonatal death); small for gestational age (SGA) birth and preterm delivery (all, early, spontaneous). We calculated per cent differences between adjusted risk ratios (aRR) from two models with maternal age, low socio-economic status, body mass index, and smoking ascertained in the index pregnancy and the subsequent pregnancy. We considered relative per cent differences <5% minimal, 5%-9% modest, and ≥10% substantial.

RESULTS

Adjustment for confounders measured at the subsequent pregnancy introduced modest bias towards the null for perinatal mortality aRRs for <6-month interpregnancy intervals [-9.7%, 95% confidence interval [CI] -15.3, -6.2). SGA aRRs were minimally biased towards the null (-1.1%, 95% CI -2.6, 0.8) for <6-month intervals. While early preterm delivery aRRs were substantially biased towards the null (-10.4%, 95% CI -14.0, -6.6) for <6-month interpregnancy intervals, bias was minimal for <6-month intervals for all preterm deliveries (-0.6%, 95% CI -2.0, 0.8) and spontaneous preterm deliveries (-1.3%, 95% CI -3.1, 0.1). For all outcomes, bias was attenuated and minimal for 6-11-month and 12-17-month interpregnancy intervals.

CONCLUSION

These findings suggest that maternally linked pregnancy data may not be needed for appropriate confounder adjustment when studying the effects of short interpregnancy interval on pregnancy outcomes.

Determinants of pre-eclampsia among pregnant women attending perinatal care in hospitals of the Omo district, Southern Ethiopia

Pre‐eclampsia is estimated to cause 70 000 maternal death globally every year, with the majority of deaths in low‐ and middle‐income countries. In Ethiopia, pre‐eclampsia causes 16% of direct maternal deaths. Despite the high burden of disease, pre‐eclampsia remains poorly studied in low and middle‐income countries. In this study, we aimed to identify risk factors for pre‐eclampsia in pregnant women attending hospitals in the Omo district of Southern Ethiopia. Data were collected via face‐to‐face interviews. Logistic regression analysis was computed to examine the relationship between the independent variable and pre‐eclampsia. An adjusted odds ratio (AOR) with the corresponding 95% confidence interval (CI) excluding 1 in the multivariable analysis was considered to identify factors associated with pre‐eclampsia at a p‐value of <0.05. A total of 167 cases and 352 controls were included. Factors that were found to have a statistically significant association with pre‐eclampsia were primary relatives who had a history of chronic hypertension (AOR 2.1, 95% CI: 1.06‐4.21), family history of diabetes mellitus (AOR 2.35; 95% CI: 1.07‐5.20), preterm gestation (AOR = 1.56, 95% CI: 1.05‐2.32), and pre‐conception smoking exposure (AOR = 4.16, 95% CI: 1.1‐15.4). The study identified that a family history of chronic illnesses and diabetes mellitus, preterm gestation, and smoking exposure before conception were the risk factors for pre‐eclampsia. Presumably, addressing the identified risk factors may give further insight into where interventions and resources should be focused, as well as having an understanding of the burden of disease.

Family history of chronic illness, preterm gestational age and smoking exposure before pregnancy increases the probability of preeclampsia in Omo district in southern Ethiopia: a case-control study

BACKGROUND

Preeclampsia is a complex syndrome that is considered a disorder specific to pregnancy. However, research indicates that diffuse maternal endothelial damage may persist after childbirth. On the other hand, women who had a history of pre-eclampsia are at an increased risk of vascular disease. Considering that the multifactorial nature of pre-eclampsia in a remote health setting, knowledge of risk factors of preeclampsia gives epidemiological significance specific to the study area. Therefore, this study aimed to identify the determinants of preeclampsia among pregnant women attending perinatal service in Omo district Hospitals in southern Ethiopia.

METHODS

An institution-based unmatched case-control study design was conducted among women visiting for perinatal service in Omo District public hospitals between February to August 2018. A total of 167 cases and 352 controls were included. Data were collected via face-to-face interviews. Bivariable and multivariable logistic regression analysis were computed to examine the effect of the independent variable on preeclampsia using Statistical Package for Social Sciences version 26 window compatible software. Variables with a p-value of less than 0.05 were considered statistically significant.

RESULTS

Factors that were found to have a statistically significant association with pre-eclampsia were primary relatives who had history of chronic hypertension (AOR 2.1, 95% CI: 1.06-4.21), family history of diabetes mellitus (AOR 2.35; 95% CI: 1.07-5.20), preterm gestation(AOR = 1.56, 95%CI, 1.05-2.32), and pre-conception smoking exposure (AOR = 4.16, 95%CI, 1.1-15.4).

CONCLUSIONS

The study identified the risk factors for pre-eclampsia. Early detection and timely intervention to manage pre-eclampsia, and obstetric care providers need to emphasize women at preterm gestation and a history of smoking before pregnancy.

Exposure to vitamin D from fortified margarine during fetal life and later risk of pre-eclampsia: the D-tect Study

OBJECTIVE

To examine if fetal exposure to a small dosage of extra vitamin D from food fortification was associated with a decrease in the risk of pre-eclampsia later in life.

DESIGN

Cancellation of the mandatory vitamin D fortification of margarine in 1985 created a societal experiment, with entire adjacent birth cohorts exposed or unexposed to extra vitamin D during fetal development. The Danish national medical health registries allowed the identification of pre-eclampsia cases later in life among all exposed and unexposed female individuals.

SETTING

Denmark.

SUBJECTS

Women born between June 1983 and August 1988, who gave birth to their first child at age 14·5-27·5 years (n 32 621).

RESULTS

OR (95 % CI) for pre-eclampsia among women exposed v. unexposed to extra vitamin D from fortification during fetal development was 0·86 (0·76, 0·97). Exposure to extra vitamin D was associated with further reduced odds of pre-eclampsia (0·49 (0·34, 0·72)) among current smokers, but not among former smokers and non-smokers.

CONCLUSIONS

Additional vitamin D in fetal life from food fortification seems to reduce the risk of pre-eclampsia later in life. The risk reduction may be particularly strong among women who smoke during pregnancy.

First-trimester smoking cessation in pregnancy did not increase the risk of preeclampsia/eclampsia: A Murmansk County Birth Registry study

Background

Although prior studies have shown that smoking reduces preeclampsia/eclampsia risk, the consequence of giving up this habit during pregnancy should be assessed. The aims of the current study were threefold: (i) describe maternal characteristics of women with preeclampsia/eclampsia; (ii) examine a possible association between the number of cigarettes smoked daily during pregnancy and the development of this affliction; and (iii) determine if first-trimester discontinuation of smoking during pregnancy influences the risk.

Methods

A registry-based study was conducted using data from the Murmansk County Birth Registry (MCBR). It included women without pre-existing hypertension, who delivered a singleton infant during 2006–2011 and had attended the first antenatal visit before 12 week of gestation. We adjusted for potential confounders using logistic regression.

Results

The prevalence of preeclampsia/eclampsia was 8.3% (95%CI: 8.0–8.6). Preeclampsia/eclampsia associated with maternal age, education, marital status, parity, excessive weight gain and body mass index at the first antenatal visit. There was a dose-response relationship between the number of smoked cigarettes per day during pregnancy and the risk of preeclampsia/eclampsia (adjusted OR_{1-5 cig/day} = 0.69 with 95%CI: 0.56–0.87; OR_{6-10 cig/day} = 0.65 with 95%CI: 0.51–0.82; and OR_{≥11 cig/day} = 0.49 with 95%CI: 0.30–0.81). There was no difference in this risk among women who smoked before and during pregnancy and those who did so before but not during pregnancy (adjusted OR = 1.10 with 95%CI: 0.91–1.32).

Conclusions

Preeclampsia/eclampsia was associated with maternal age, education, marital status, parity, excessive weight gain, and body mass index at the first antenatal visit. There was a negative dose-response relationship between the number of smoked cigarettes per day during pregnancy and the odds of preeclampsia/eclampsia. However, women who gave up smoking during the first trimester of gestation had the same risk of preeclampsia/eclampsia as those who smoked while pregnant. Consequently, antenatal clinic specialists are advised to take these various observations into account when counselling women on smoking cessation during pregnancy.

Cigarette smoking during pregnancy and preeclampsia risk: a systematic review and meta-analysis of prospective studies

Although evidence from epidemiological studies evaluating the association between cigarette smoking during pregnancy and preeclampsia risk has been systematically reviewed, the findings have been out of date. To further clarify the relationship, we conducted this comprehensive meta-analysis of prospective studies. We searched PubMed and Web of Science up to August 2015 to identify prospective studies that evaluated the association between cigarette smoking during pregnancy and preeclampsia risk. Random-effects models were used to estimate summarized relative risk (RR) and 95% confidence intervals (CIs). Seventeen prospective studies involving 62,089 preeclampsia patients from a total of approximately 1.8 million subjects were included. Overall, there was a significant negative association between smoking during pregnancy and incidence of preeclampsia (RR = 0.67, 95% CI: 0.60–0.75), with significant heterogeneity (I² = 91.7%). Such an inverse association was also detected in strata of subgroup analyses according to study location, study sample size, parity of populations, singleton pregnancy, and adjustment for potential confounders including maternal age, diabetes mellitus, chronic hypertension, body mass index, and gender of infant. In summary, this meta-analysis suggests that smoking during pregnancy is inversely associated with incidence of preeclampsia. Further large scale multi-center prospective studies are warranted to validate our findings.

Maternal overweight and obesity and risk of pre-eclampsia in women with type 1 diabetes or type 2 diabetes

AIMS/HYPOTHESIS

Women with type 1 or type 2 diabetes are at increased risk of pre-eclampsia. Overweight and obesity are associated with an increased risk of pre-eclampsia in women without diabetes. The aim of the study was to investigate the impact of maternal overweight and obesity on the risk of pre-eclampsia in women with type 1 diabetes or type 2 diabetes.

METHODS

In a population-based cohort study including singleton births in Sweden, we estimated the risk of pre-eclampsia among women with type 1 diabetes (n = 7062) and type 2 diabetes (n = 886), and investigated whether maternal overweight (BMI 25-29.9 kg/m(2)) and obesity (BMI ≥30.0 kg/m(2)) modified the risk. Logistic regression analyses were used to estimate crude and adjusted ORs with 95% CIs, using women without diabetes as the reference group (n = 1,509,525).

RESULTS

Compared with women without diabetes, the adjusted ORs for pre-eclampsia in women with type 1 and type 2 diabetes were 5.74 (95% CI 5.31, 6.20) and 2.11 (95% CI 1.65, 2.70), respectively. The corresponding risks of pre-eclampsia combined with preterm birth were even higher. Risks of pre-eclampsia increased with maternal overweight (BMI 25-29.9 kg/m(2)) and obesity (BMI ≥30.0 kg/m(2)), foremost in women without diabetes, to a lesser extent in women with type 1 diabetes but not in women with type 2 diabetes.

CONCLUSIONS/INTERPRETATION

Maternal overweight and obesity increased risks of pre-eclampsia in women with type 1 diabetes but not in women with type 2 diabetes. Even so, considering associations between maternal BMI and overall maternal and offspring risk, all women (with and without diabetes) should aim for a normal weight before pregnancy.

Obesity in young age is a risk factor for preeclampsia: a facility based case-control study, northwest Ethiopia

BACKGROUND

Preeclampsia is one of the most commonly encountered hypertensive disorders of pregnancy. For many years, obesity has been suggested to play a role in preeclampsia. However, the hypotheses have been diverse and often revealed inconsistent results. This study has aimed to estimate the effect of obesity and dietary habits on preeclampsia in Bahir Dar City, north-western Ethiopia.

METHODS

A facility-based unmatched case-control study was conducted on 453 (151 cases and 302 controls) pregnant women, attending antenatal care or skilled delivery at Bahir Dar City. Data were collected through face to face interviews and measurements of mid-upper-arm circumference (MUAC) at the time of the interviews. Data were cleaned and entered into IBM SPSS version 20 and later analyzed using STATA version 12. Univariate and multivariate logistic regression analyses were employed to estimate the effect of independent variables on preeclampsia. Stratified analysis was conducted to check for presence of confounding and/or effect modification between covariates.

RESULT

The odds of preeclampsia were higher among obese (MUAC ≥25 cm) women than their leaner counterparts (AOR = 3.33, 95 % CI: 1.87, 5.79). Obesity was also found to have a similar magnitude of risk for late onset preeclampsia (AOR = 3.63, 95 % CI: 1.89, 6.97). When stratified by age, the effect of obesity on overall and late onset preeclampsia was significant among young (age < 35 years) women (COR = 1.81, 95 % CI: 1.11, 2.99) and (COR = 2.09, 95 % CI: 1.16, 3.86), respectively. As the age groups became more homogenous through adjusted stratification, obesity showed a particularly significant effect in women age ≤24 and 25-29 years; (AOR = 2.31, 95 % CI: 1.06, 5.12) and (AOR = 3.66, 95 % CI: 1.37, 10.87) respectively. Similarly, the effect of obesity on late onset preeclampsia was evident among younger women age ≤24 and 25-29 years; (AOR = 3.16, 95 % CI: 1.21, 8.24) and (AOR = 1.98, 95 % CI: 1.16, 3.40) respectively. However, obesity has no significant effect on early onset of preeclampsia (AOR = 1.98, 95 % CI: 0.79, 4.94). On the other hand, compliance to folate supplementation during pregnancy and fruit consumption were associated with reduced risk of preeclampsia.

CONCLUSION

Obesity in young age was found to be a risk factor for preeclampsia while compliance to folate supplement and adequate fruit consumption were found to be protective against preeclampsia. Promoting healthy life style, including body weight control, consumption of fruits and vegetables, and folate supplementation should be promoted to reduce the risk of preeclampsia.

Deconstructing the smoking-preeclampsia paradox through a counterfactual framework

Although smoking during pregnancy may lead to many adverse outcomes, numerous studies have reported a paradoxical inverse association between maternal cigarette smoking during pregnancy and preeclampsia. Using a counterfactual framework we aimed to explore the structure of this paradox as being a consequence of selection bias. Using a case-control study nested in the Icelandic Birth Registry (1309 women), we show how this selection bias can be explored and corrected for. Cases were defined as any case of pregnancy induced hypertension or preeclampsia occurring after 20 weeks' gestation and controls as normotensive mothers who gave birth in the same year. First, we used directed acyclic graphs to illustrate the common bias structure. Second, we used classical logistic regression and mediation analytic methods for dichotomous outcomes to explore the structure of the bias. Lastly, we performed both deterministic and probabilistic sensitivity analysis to estimate the amount of bias due to an uncontrolled confounder and corrected for it. The biased effect of smoking was estimated to reduce the odds of preeclampsia by 28 % (OR 0.72, 95 %CI 0.52, 0.99) and after stratification by gestational age at delivery (<37 vs. ≥37 gestation weeks) by 75 % (OR 0.25, 95 %CI 0.10, 0.68). In a mediation analysis, the natural indirect effect showed and OR > 1, revealing the structure of the paradox. The bias-adjusted estimation of the smoking effect on preeclampsia showed an OR of 1.22 (95 %CI 0.41, 6.53). The smoking-preeclampsia paradox appears to be an example of (1) selection bias most likely caused by studying cases prevalent at birth rather than all incident cases from conception in a pregnancy cohort, (2) omitting important confounders associated with both smoking and preeclampsia (preventing the outcome to develop) and (3) controlling for a collider (gestation weeks at delivery). Future studies need to consider these aspects when studying and interpreting the association between smoking and pregnancy outcomes.

Effects of maternal smoking on the placental expression of genes related to angiogenesis and apoptosis during the first trimester

OBJECTIVE

Maternal cigarette smoking is reportedly associated with miscarriage, fetal growth restriction and placental abruption, and is paradoxically associated with a decreased risk of developing preeclampsia. In the present study, we investigated the gene expression levels of villous tissues in early gestation. We compared the expression levels of the genes related to angiogenesis and apoptosis in the villous tissues obtained from smoking and non-smoking pregnant women.

MATERIALS AND METHODS

We collected villous tissue samples from 57 women requesting surgical termination due to non-medical reasons at 6-8 weeks of gestation. The maternal cigarette smoking status was evaluated by the level of serum cotinine and patients were divided into active smokers and non-smokers by the serum cotinine level. The placental levels of VEGFA, PGF, FLT1, HIF1A, TP53, BAX and BCL2 mRNA were quantified by real time PCR.

RESULTS

The gene expression level of PGF and HIF1A in the active smoker group was significantly higher than that in the non-smoker group. We did not observe any significant differences in the VEGFA or FLT1 expression between the groups. In active smoker group, the gene expression levels of TP53 and BAX were significantly higher than those in the non-smoker group. The ratio of BAX/BCL2 mRNA in the active smoker group was significantly higher than that in the non-smoker group.

CONCLUSIONS

Our findings revealed that smoking might affect the placenta during early pregnancy. Maternal cigarette smoking in early pregnancy may be associated with villus hypoxia, which may influence angiogenesis and apoptosis.

Pre-eclampsia and assisted reproductive technologies: consequences of advanced maternal age, interbirth intervals, new partner and smoking habits

OBJECTIVE

To examine the risk of pre-eclampsia (PE) in women conceiving after assisted reproductive technologies (ART). Potential confounding from maternal age, long intervals between births, new partner and smoking were evaluated.

DESIGN AND SETTING

Population-based cohort study with data from the Medical Birth Registry of Norway.

POPULATION

A total of 501,766 mothers with offspring from 1988 to 2009.

METHODS

Births to the same mother were linked in sibship data files with information of ART.

MAIN OUTCOME MEASURES

Odds ratio (OR) (95% confidence intervals) of PE in pregnancies conceived by ART compared with spontaneous conception, stratified by parity.

RESULTS

The prevalence of PE was 5.1% in first, 2.2% in second and 2.1% in third pregnancies. Corresponding figures in ART pregnancies were 6.0%, 3.3% and 4.4%. Hence, the odds ratios of PE in ART pregnancies relative to spontaneous pregnancies increased from 1.2 (1.1-1.3) in first, 1.5 (1.3-1.8) in second to 2.1 (1.4-3.3) in third pregnancies. Adjusting by maternal age lowered the odds ratio to 1.3 (1.1-1.6) and 1.8 (1.2-2.8) in second and third pregnancies, respectively. Multi-adjusted, birth interval had more impact than change of partner. Smoking was associated with a strongly reduced PE risk (odds ratio 0.65; 0.62-0.69), but there was no confounding by smoking on the ART associated risk.

CONCLUSIONS

Assisted reproductive technologies increases the risk of PE, and the risk may increase by parity. The association between ART pregnancies and PE is to some extent explained by interbirth intervals and advanced maternal age, but not to change of partner or smoking.