Prepregnancy Body Mass Index Status Research Articles

Extreme temperature exposure increases the risk of preterm birth in women with abnormal pre-pregnancy body mass index: a cohort study in a southern province of China.

Prior literature has found that extreme temperature exposure is associated with preterm birth (PTB). However, current evidence provides heterogeneous conclusions, and data on extreme cold and across different pre-pregnancy body mass index (BMI) statuses are limited. We conducted a population-based retrospective cohort of 251,257 women between 2014 and 2017 in Guangdong, China, to evaluate whether the association between extreme temperature exposure and PTB varied in pre-pregnancy BMI status. Participants were divided into three categories based on pre-pregnancy BMI: underweight (BMI < 18.5 kg/m2), normal weight (18.5-23.9 kg/m2), overweight or obesity (≥ 24.0 kg/m2). We fitted Cox proportional hazards models to assess the association between daily mean temperature and PTB at each trimester for each BMI category separately. The hazard ratios (HRs) at the 5th and 95th percentiles of temperature (defined as low and high temperatures respectively) were provided using the median temperature at each trimester as a reference. 58,220 (23.2%) were underweight, and 27,865 (11.1%) were overweight or obese. Of the 251,257 women, 18,612 (7.41%) had PTB delivery. Both low-and high-temperature exposure increased the risk of PTB in the third trimester, while cold exposure mostly mitigated the risk for the first and second trimesters. The association with low temperature was the strongest in the third trimester, especially for underweight women (HR: 1.825; 95%CI: 1.529 ~ 2.179), while the association with high temperature was the strongest also in the third trimester, especially for obese or overweight women (HR:1.825; 95%CI:1.502 ~ 2.218). Furthermore, the attributable fractions of PTB risk in the third trimester were estimated as 5.59% (95% CI: 3.58, 7.98%) for cold exposure among underweight women and 3.31% (95% CI: 2.01, 4.88%) for hot exposure among overweight or obese women. Exposure to either low temperature in the third trimester or high temperature during pregnancy was associated with a higher risk of PTB. Moreover, pre-pregnancy BMI status might affect the susceptibility of pregnant women. Such findings would be useful to develop targeted measures for vulnerable populations.

Association of Gestational Hypertension and Eclampsia to Maternal Smoking by Pre-Pregnancy Body Mass Index Status Among Aged 20-29-Years in the United States

Objective To investigate whether gestational hypertension (GH) and/or eclampsia was associated with the timing of maternal smoking when stratified by pre-pregnancy body mass index (pBMI) status. Study Design and Methods 1,376,271 US-born mothers aged 20-29 from the 2019 infant natality data who had a singleton birth (20+ weeks of gestation) were analyzed in this study. Maternal smoking status was defined into five groups, i.e., non-smokers, quitted smoking before pregnancy, quitted smoking before the 2nd trimester, quitted smoking before the 3rd trimester, and smoked whole-time. Odds ratios (ORs) of GH or eclampsia were estimated separately using multiple logistic regression for maternal smoking by pBMI status (kg/m2): underweight (&lt;18.5), normal (18.5≤25.0), overweight (25.0≤30.0), and obese (≥30.0). Results Compared to non-smokers, the adjusted ORs (95% CIs) of GH for mothers who quit before pregnancy with pBMI underweight, normal, overweight, and obese were 1.17 (0.92-1.49), 1.11 (1.03-1.19), 1.13 (1.05-1.22), 1.13 (1.08-1.19), respectively. While the ORs (95% CIs) of GH for mothers who smoked for the entirety of their pregnancy were 0.71 (0.60-0.84), 0.80 (0.75-0.84), 0.79 (0.74-0.84), and 0.82 (0.78-0.85), respectively. The adjusted ORs for eclampsia showed a different pattern, only that for mothers who smoked for their whole pregnancy with normal and obese showed significantly (0.69 (0.53-0.91) for normal weight, 0.73 (0.58-0.92) for obese). Conclusion In comparison to non-smokers, an increase in the odds of GH were observed amongst normal, overweight, and obese mothers quitting before pregnancy meanwhile a decreased odds were observed amongst mothers smoking throughout pregnancy in all pBMI classes.

Maternal pre-pregnancy BMI and offspring hyperactivity-inattention trajectories from 3 to 8years in the EDEN birth cohort study.

Evidence suggests obesity during pregnancy is associated with offspring attention-deficit hyperactivity disorder. However, studies have been limited to evaluating the association at a single age with inadequate data on important maternal lifestyle confounders and unmeasured familial confounding. The objective of this study was to examine the association between maternal pre-pregnancy body mass index (BMI) and child hyperactivity-inattention symptoms (HIS) at 3, 5 and 8years. Data came from the EDEN mother-child cohort. Maternal pre-pregnancy BMI status (kg/m2) was calculated using pre-pregnancy weight and height (self-reported by mothers or measured by midwives). HIS were assessed by parental-report on the Strengths and Difficulties Questionnaire at 3, 5 and 8years of age and used to derive developmental trajectories of HIS (n = 1428). Multivariate models were adjusted for confounders including socioeconomic status, maternal lifestyle behaviours (exercise, diet, smoking, alcohol), childcare and a stimulating home environment. Paternal BMI was used as a negative control. Compared to a normal pre-pregnancy BMI, pre-pregnancy maternal obesity was positively associated with increased odds of a high HIS trajectory between 3 and 8years old in both unadjusted and adjusted logistic regression (adjusted odds ratio [aOR] 1.87 [95% CI 1.12, 3.12]). Pre-pregnancy overweight was not significantly associated after adjustment for confounders (aOR 1.32 [0.87, 2.01]). Maternal pre-pregnancy obesity, but not overweight, was associated with increased likelihood of a high HIS trajectory in children from 3 to 8years old. This association persisted despite controlling for many important maternal lifestyle factors and paternal BMI. Further research is warranted to identify possible mediators involved.

Risk of large for gestational age births at early, full and late term in relation to pre-pregnancy body mass index: Mediation by gestational diabetes status.

Maternal pre-pregnancy body mass index (BMI) is strongly associated with infant birthweight and the risk differs in pregnancies complicated by gestational diabetes (GDM). To examine the risk of large for gestational age (LGA) (≥97th percentile) singleton births at early term, full term and late term in relation to maternal pre-pregnancy BMI status mediated through GDM. We analysed data from the 2018 U.S. National Vital Statistics Natality File restricted to singleton term births (N=3,229,783). In counterfactual models for causal inference, we estimated the total effect (TE), natural direct effect (NDE) and natural indirect effect (NIE) for the association of pre-pregnancy BMI with subcategories of LGA births at early, full and late term mediated through GDM, using log-binomial regression and adjusting for race/ethnicity, age, education, parity and infant sex. Proportion mediated was calculated on the risk difference scale and potential unmeasured confounders were assessed using the E-value. Overall, 6.4% of women had GDM, and there were 3.6% LGA singleton term births. The highest prevalence of GDM was among pre-gestational overweight/obesity that also had the highest rates of LGA births at term. The TE estimates for the risk of LGA births were the strongest across women with higher pre-pregnancy BMI compared to women with normal pre-pregnancy BMI. The NDE estimates were higher than the NIE estimates for overweight/obese BMI status. The proportion mediated, which answers the causal question to what extent the total effect of the association between pre-pregnancy BMI and LGA births is accounted for through GDM, was the highest (up to 16%) for early term births. Term singleton births make up the largest proportion in a cohort of newborns. While the percentage mediated through GDM was relatively small, health risks arising from pre-pregnancy overweight, and obesity can be substantial to both mothers and their offspring.

The mediating role of gestational diabetes mellitus in the associations of maternal prepregnancy body mass index with neonatal birth weight.

BackgroundBoth prepregnancy obesity and gestational diabetes mellitus (GDM) have been linked to adverse neonatal birth weight. However, the mediating role of GDM between prepregnancy obesity and neonatal birth weight is unclear.MethodThe cohort study included 17 260 singleton pregnant women and their newborns. Participants' demographic characteristics, disease history, family history of the disease, and the perinatal outcomes were recorded. The association between maternal prepregnancy body mass index (BMI) status and small for gestational age (SGA) or large for gestational age (LGA) neonates was analyzed using logistic regressions, before and after adjusting for covariates and GDM. The potential mediation of GDM on the association between prepregnancy BMI and adverse birth weight was examined.ResultMultivariate logistic regression demonstrated that prepregnancy underweight women were more likely to deliver SGA neonates compared to those who had normal weights, whereas prepregnancy obese pregnant women were more likely to have LGA neonates. The RMediation analyses illustrated that the mediation effect of GDM on the maternal prepregnancy BMI (continuous variable) and the risk of SGA was not significant, whereas the association between prepregnancy BMI and LGA was statistically mediated by GDM (95%CI of a*b: 0.009‐0.051). The Iacobacci (2012) method indicated that the impact of maternal prepregnancy overweight (Zmediation = 2.418, P = .015) and obesity (Zmediation = 2.165, P = .030) on LGA was partially mediated by GDM, with an indirect effect of 16.3% and 13.1%, respectively.ConclusionPrepregnancy BMI was observed to be associated with SGA and LGA. The association of prepregnancy overweight and obesity with LGA was found to be partially mediated by GDM.

Pre-pregnancy BMI-associated miRNA and mRNA expression signatures in the placenta highlight a sexually-dimorphic response to maternal underweight status

Pre-pregnancy body mass index (BMI) is associated with adverse pregnancy and neonatal health outcomes, with differences in risk observed between sexes. Given that the placenta is a sexually dimorphic organ and critical regulator of development, examining differences in placental mRNA and miRNA expression in relation to pre-pregnancy BMI may provide insight into responses to maternal BMI in utero. Here, genome-wide mRNA and miRNA expression levels were assessed in the placentas of infants born extremely preterm. Differences in expression were evaluated according to pre-pregnancy BMI status (1) overall and (2) in male and female placentas separately. Overall, 719 mRNAs were differentially expressed in relation to underweight status. Unexpectedly, no genes were differentially expressed in relation to overweight or obese status. In male placentas, 572 mRNAs were associated with underweight status, with 503 (70%) overlapping genes identified overall. Notably, 43/572 (8%) of the mRNAs associated with underweight status in male placentas were also gene targets of two miRNAs (miR-4057 and miR-128-1-5p) associated with underweight status in male placentas. Pathways regulating placental nutrient metabolism and angiogenesis were among those enriched in mRNAs associated with underweight status in males. This study is among the first to highlight a sexually dimorphic response to low pre-pregnancy BMI in the placenta.

Prevalence and temporal trends in prepregnancy nutritional status and gestational weight gain of adult women followed in the Brazilian Food and Nutrition Surveillance System from 2008 to 2018.

Prepregnancy body mass index (BMI) and gestational weight gain (GWG) are the most investigated indicators of maternal nutritional status, which is a modifiable factor that plays a vital role in maternal and infant health. This study describes prepregnancy BMI and GWG of 840,243 women with 2,087,765 weight observations in the Brazilian Food and Nutrition Surveillance System from 2008 to 2018. Prepregnancy BMI was classified according to the World Health Organization cut‐offs. Total GWG was calculated from weight measurements taken after 36 weeks of pregnancy and classified according to the Institute of Medicine guidelines. Temporal trends in prepregnancy BMI status were examined, and maps were used to evaluate changes in excessive GWG in each Brazilian federation unit. On overall, prepregnancy overweight and obesity increased from 22.6% to 28.8% and from 9.8% to 19.8%, respectively, between 2008 and 2018. The prevalence of excessive GWG rose from 34.2% to 38.7% during the same period and in 11 of the 27 Brazilian federation units between 2008 and 2016. Women with underweight showed the highest values for mean total GWG for all the compared years (overall variation from 12.3 to 13.1 kg), followed by those with normal weight (11.9 to 12.5 kg), overweight (10.1 to 10.9 kg) and obesity (from 8.2 to 8.9 kg). Within each BMI group, values remained fairly stable throughout the studied period for first‐ and second‐trimester GWG and total GWG. These results help to fill a significant gap in understanding the distribution of prepregnancy BMI and GWG in Brazilian women.

Pre-pregnancy body mass index classification and gestational weight gain on neonatal outcomes in adolescent mothers: A follow-up study.

Introduction: Institute of Medicine gestational weight gain recommendations are based on body mass index (BMI) status using adult cut-off points for women of all ages, even though adolescents have specific criteria, like WHO and CDC, so adolescents can receive inadequate weight gain recommendations. Objectives: To estimate the proportion of classification disparity between the three criteria (WHO, CDC and IOM) of pre-pregnancy BMI status; and to analyze neonatal outcomes according to weight gain recommendation based on pre-pregnancy BMI using the three criteria. Methods: Follow-up study in pregnant adolescents 12–19 years. Sociodemographic, anthropometric and pregnancy data were obtained. Percentage of pre-pregnancy BMI classification disparity was calculated between three criteria. Gestational weight gain was categorized in adequate, low and high according to IOM. Regression models were used to analyze negative neonatal outcomes. Results: 601 pregnant adolescents were included, mean age was 16±1.4 years. For pre-pregnancy BMI classification, 28.5% had classification disparity using IOM vs WHO, and 14% when comparing IOM vs CDC. Greater classification disparity was observed as BMI increased. When using WHO categories, a high weight gain was associated with increased risk of having a low birth weight baby (OR: 1.91, CI95%: 1.03–3.53). For CDC criteria, a low weight gain was associated with increased risk of having a preterm baby (OR: 2.65; CI95%: 1.16–6.08) and a high weight gain was associated with low birth weight (OR: 2.10; CI95%: 1.10–4.01). For IOM criteria, a weight gain either low or high were associated with increased risk of low birth weight and preterm birth. Conclusion: There is pre-pregnancy BMI classification disparity using criteria for adolescents compared to adult criteria. Nevertheless, with WHO and CDC only a high gestational weight gain was a risk for negative neonatal outcome. It is important to have a BMI classification system for adolescents that better predicts neonatal outcomes.

Association of Pre-pregnancy BMI and Postpartum Weight Retention Before Second Pregnancy, Washington State, 2003-2013.

Background Maternal overweight and obesity is one of the most common high-risk obstetric conditions associated with adverse birth outcomes. Smaller studies have suggested that pre-pregnancy body mass index (BMI) is associated with postpartum weight retention. Objective The primary objective of this study was to examine the association between pre-pregnancy BMI status and maternal weight retention. Study design We conducted a population-based retrospective cohort study using Washington State birth certificate data from 2003-2013. We included women who had two sequential births during this time period, with the second birth occurring within 18-36months of the first singleton delivery date. BMI before a women's first pregnancy ("pre-pregnancy BMI") was categorized as normal (18.5-24.9kg/m2) and overweight/obese (25-40kg/m2). Women were classified as having returned to first pre-pregnancy BMI if their BMI before their second pregnancy was no more than 1kg/m2 more compared to their BMI before their first pregnancy. Analyses were stratified by gestational weight gain during the first pregnancy (below, met, exceeded recommended gestational weight gain). Results A total of 49,132 mothers were included in the study. Among women who met their recommended gestational weight gain, compared to mothers with a normal BMI, obese/overweight mothers were less likely to return to their pre-pregnancy BMI (76.5 vs 72.3%; RRObese/Overweight = 0.88; 95% CI: 0.85-0.92). A similar pattern was observed among women who exceeded their recommended gestational weight gain (62.6 vs 53.2%; RRObese/Overweight = 0.79, 95% CI: 0.78-0.80). Conclusion Pre-pregnancy BMI in the overweight/obese range is associated with a decreased likelihood of returning to pre-pregnancy BMI. Further research to support women during and after their pregnancy to promote behavior changes that prevent excessive weight gain during pregnancy and weight retention after birth is needed.

Associations between parity and maternal BMI in a population-based cohort study.

We aimed to investigate the change in prevalence of overweight and obesity in pregnant Danish women from 2004 to 2012, and investigate whether increasing parity was associated with a change in body mass index (BMI) prevalence. We obtained a population-based cohort from the Danish Medical Birth Registry consisting of all Danish women giving birth in 2004-2012 (n = 572 321). This registry contains information on 99.8% of all births in Denmark. We calculated the overall change in prepregnancy BMI status among pregnant women in Denmark, and a multiple linear regression model with adjustment for several potential confounders was used to examine the change in prepregnancy BMI with increasing parity. In 2004, the prevalence of prepregnancy overweight and obesity (BMI ≥ 25) and obesity alone (BMI ≥ 30) was 31.9 and 11%, respectively. In 2012, the prevalence had reached 34.2 and 12.8%. The mean BMI increased for every additional parity from 23.80 (95% CI 23.77-23.82) in parity group 1 to 26.70 (26.52-26.90) in parity group 5+. A multiple linear regression adjusted for potential confounders showed that women on average gained 0.62 (0.58-0.65) BMI units after every additional birth. This study showed a 7.2% increase in overweight and obesity (BMI ≥ 25) and a 16.4% increase in obesity alone (BMI ≥ 30) for pregnant women in Denmark from 2004 to 2012. In addition, an increase in interpregnancy BMI was seen at every additional delivery, suggesting that obesity is an increasing challenge in obstetrics.

Adherence to Canada’s Food Guide Recommendations during Pregnancy

BackgroundIn Canada, pregnant women are typically referred to Canada’s Food Guide (CFG), a set of national dietary recommendations designed to promote adequate nutrient intake. Pregnant women are also advised to gain weight within the Institute of Medicine guidelines, which differ by prepregnancy body mass index (BMI). However, CFG recommendations do not account for prepregnancy BMI and provide no guidance on “less healthy” (LH) foods. ObjectiveThe aim of this study was to score women’s diets according to adherence to CFG recommendations and consumption of LH foods and to examine differences between these diet scores by prepregnancy BMI. MethodsParticipants enrolled in the APrON (Alberta Pregnancy Outcomes and Nutrition) prospective cohort study completed a 24-h recall in their second trimester (n = 1630). A score was created on the basis of each daily dietary CFG recommendation met, ranging from 0 to 9. The distribution of consumption (grams per day) of 8 LH food groups was given a score of 0 (none) or 1, 2, or 3 (representing the lowest, middle, or highest tertiles, respectively) and summed giving a total LH score of 0–24. ResultsThere were few differences in CFG recommendations met by prepregnancy BMI status, although fewer women who were overweight or obese prepregnancy met the specific recommendation to consume 7–8 servings of fruit or vegetables/d than did those who were under- or normal weight (47% and 41% compared with 50% and 54%, respectively). Although differences were small, women who were obese prepregnancy had lower CFG scores (β = −0.28; 95% CI:−0.53, −0.02) and higher LH scores (β = 0.45; 95% CI: 0.04, 0.86) than did those who were normal weight. ConclusionThe study results suggest that more attention may need to be paid to individualized counseling on dietary recommendations that take account of prepregnancy BMI.

Prevalence of metabolic syndrome markers among women at 1-year postpartum as per prepregnancy body mass index status: A longitudinal study

Introduction:Maternal body composition (BC) changes during lactation. Increased prepregnancy obesity is associated with poor obstetric outcomes. The aim was to study changes in maternal BC postpartum (PP) to 1-year PP with reference to their prepregnancy body mass index (BMI) status.Methods:The study design was a 1-year follow-up study. Sixty-five apparently healthy primiparous women (28.6 ± 3.4 years delivered full-term infants) were randomly selected from December 2010 to June 2013 and postclassified on the basis of their prepregnancy BMI status. Anthropometry, sociodemographic status, physical activity, diet, clinical examination, biochemical tests, and BC at total body (dual energy X-ray absorptiometry, GE, Lunar DPX) were collected using standardized protocols.Results:Forty-one women were classified in Group A with normal prepregnancy BMI (20.4 ± 2.0 kg/m2) and 24 women in Group B with overweight/obese (OW/OB) prepregnancy BMI (26.1 ± 1.9 kg/m2). At 1 year, 75% of women returned to normal BMI in Group A, whereas all 100% of women from Group B remained in OW category at 1-year PP. Nearly 43% of Group B women showed the presence of at least two metabolic syndrome risk factors as compared to 36% in Group A at 1 year.Conclusion:Women with OW/OB prepregnancy BMI accumulated higher visceral fat with a higher prevalence of metabolic risk factors at 1-year PP. Our study underlines the importance of maintaining BMI status in reference range in reproductive years.

Association between body mass index and the timing of pregnancy recognition and entry into prenatal care.

To assess whether prepregnancy body mass index (BMI) is independently associated with the timing of pregnancy recognition and initiation of prenatal care. Data from 2009 to 2010 were obtained from the Centers for Disease Control and Prevention's Pregnancy Risk Assessment Monitoring System. The 30 participating states contacted sampled mothers 2-4 months after delivery and had them complete the standardized Pregnancy Risk Assessment Monitoring System questionnaire. Prepregnancy BMI was calculated from the participants' self-reported prepregnancy weight and height. Timing of pregnancy recognition and initiation of prenatal care were also self-reported on the questionnaire. Among the 72,913 participants, 69,872 (96%) met the eligibility criteria for analysis. After adjustment for maternal race, ethnicity, smoking status in the 3 months before pregnancy, pregnancy intentions, insurance status, maternal age, marital status, maternal education, and parity, there was no association between prepregnancy BMI status and the week of pregnancy recognition. Obese women initiated prenatal care 0.20 weeks earlier on average compared with normal-weight women, although the difference was not clinically important (mean difference -0.20, 95% confidence interval [CI] -0.38 to -0.03). When examining the odds of receiving late or no prenatal care, there was no association with prepregnancy BMI. Uninsured women, however, reported initiating prenatal care almost 3 weeks later on average than privately insured women (mean difference 2.83, 95% CI 2.27-3.38) and had a more than fourfold increased odds of receiving late or no prenatal care (odds ratio 4.04, 95% CI 3.13-5.23). Prepregnancy BMI was not meaningfully associated with a delay in pregnancy recognition or with increased odds of receiving late or no prenatal care.

Gestational weight gain and child weight status at 5 years of age: differential effects by prepregnancy body mass index status

In 2009, IOM released recommendations for gestational weight gain (GWG) and noted a data gap on associations with long‐term outcomes, specifically child weight. Currently the mediating role of birthweight and heterogeneity by prepregnancy BMI are unclear. We used the nationally representative Early Childhood Longitudinal Study‐Birth Cohort to examine associations between GWG and subsequent child weight measured at 5 y. We used regression and path analysis to examine direct and indirect effects mediated by birthweight. Among underweight, normal, overweight and obese women, respectively, prevalence of excessive GWG (above recommendations) was 26%, 38%, 62% and 53%, and child obesity (BMI ≥ 95th percentile) was 9%, 13%, 19% and 27%. Multivariable logistic regression indicated null associations between inadequate GWG and child obesity for all prepregnancy BMI groups, but a significant association with excessive GWG among only normal [OR 1.8 (95% CI 1.3, 2.5)] and overweight [OR 2.0 (95% CI 1.1, 3.4)] women. Path analysis with child BMI z‐score further indicated that among normal and overweight women the direct effect of GWG was stronger than the indirect effect. Among obese women, there was no significant total effect of GWG. Our findings indicate that IOM GWG recommendations are appropriate in the context of child weight; prevention of excessive GWG may be a strategy to prevent child obesity.Grant Funding Source: Oak Ridge Institute for Science and Education (ORISE)

Racial/ethnic differences in the percentage of gestational diabetes mellitus cases attributable to overweight and obesity, Florida, 2004-2007.

Gestational diabetes mellitus (GDM) affects 3% to 7% of pregnant women in the United States, and Asian, black, American Indian, and Hispanic women are at increased risk. Florida, the fourth most populous US state, has a high level of racial/ethnic diversity, providing the opportunity to examine variations in the contribution of maternal body mass index (BMI) status to GDM risk. The objective of this study was to estimate the race/ethnicity-specific percentage of GDM attributable to overweight and obesity in Florida. We analyzed linked birth certificate and maternal hospital discharge data for live, singleton deliveries in Florida from 2004 through 2007. We used logistic regression to assess the independent contributions of women's prepregnancy BMI status to their GDM risk, by race/ethnicity, while controlling for maternal age and parity. We then calculated the adjusted population-attributable fraction of GDM cases attributable to overweight and obesity. The estimated GDM prevalence was 4.7% overall and ranged from 4.0% among non-Hispanic black women to 9.9% among Asian/Pacific Islander women. The probability of GDM increased with increasing BMI for all racial/ethnic groups. The fraction of GDM cases attributable to overweight and obesity was 41.1% overall, 15.1% among Asians/Pacific Islanders, 39.1% among Hispanics, 41.2% among non-Hispanic whites, 50.4% among non-Hispanic blacks, and 52.8% among American Indians. Although non-Hispanic black and American Indian women may benefit the most from prepregnancy reduction in obesity, interventions other than obesity prevention may be needed for women from other racial/ethnic groups.