Increasing prepregnancy body mass index: analysis of trends and contributing variables

Association between obesity during pregnancy and increased use of health care

BACKGROUND

In the United States, obesity during pregnancy is common and increases obstetrical risks. An estimate of the increase in use of health care services associated with obesity during pregnancy is needed.

METHODS

We used electronic data systems of a large U.S. group-practice health maintenance organization to identify 13,442 pregnancies among women 18 years of age or older at the time of conception that resulted in live births or stillbirths. The study period was between January 1, 2000, and December 31, 2004. We assessed associations between measures of use of health care services and body-mass index (BMI, defined as the weight in kilograms divided by the square of the height in meters) before pregnancy or in early pregnancy. The women were categorized as underweight (BMI <18.5), normal (BMI 18.5 to 24.9), overweight (BMI 25.0 to 29.9), obese (BMI 30.0 to 34.9), very obese (BMI 35.0 to 39.9), or extremely obese (BMI > or =40.0). The primary outcome was the mean length of hospital stay for delivery.

RESULTS

After adjustment for age, race or ethnic group, level of education, and parity, the mean (+/-SE) length of hospital stay for delivery was significantly (P<0.05) greater among women who were overweight (3.7+/-0.1 days), obese (4.0+/-0.1 days), very obese (4.1+/-0.1 days), and extremely obese (4.4+/-0.1 days) than among women with normal BMI (3.6+/-0.1 days). A higher-than-normal BMI was associated with significantly more prenatal fetal tests, obstetrical ultrasonographic examinations, medications dispensed from the outpatient pharmacy, telephone calls to the department of obstetrics and gynecology, and prenatal visits with physicians. A higher-than-normal BMI was also associated with significantly fewer prenatal visits with nurse practitioners and physician assistants. Most of the increase in length of stay associated with higher BMI was related to increased rates of cesarean delivery and obesity-related high-risk conditions.

CONCLUSIONS

Obesity during pregnancy is associated with increased use of health care services.

Maternal obesity: pregnancy complications, gestational weight gain and nutrition

The obesity epidemic affects all, including women of reproductive age. One in five women attending prenatal care in the UK is obese. Prepregnancy obesity is associated with serious short- and long-term complications for mother and child. Furthermore, gestational weight gain (GWG) of obese pregnant women generally exceeds the Institute of Medicine recommended ranges. This observation can partially be explained by an unbalanced diet and lack of daily physical activity. Despite this, few lifestyle intervention trials in obese pregnant women are available. Two out of seven intervention trials focusing on GWG, nutrition and physical activity, reached a significant decrease in GWG. Developing guidelines to promote appropriated weight gain and healthy lifestyle in overweight and obese pregnant women remains a challenge. This review aims to summarize the complications associated with maternal prepregnancy overweight and obesity and to discuss possible strategies to improve the lifestyle habits of pregnant women.

Does gestational weight gain affect the risk of adverse maternal and infant outcomes in overweight women?

OBJECTIVE

To examine the association between gestational weight gain and adverse maternal and infant outcomes among overweight women [body mass index (BMI) 26.0-29.0 kg/m(2)].

METHODS

A population-based cohort study using birth certificate data (1990-2004) from 34,143 singleton, full-term deliveries to nulliparous, Missouri residents ages 18-35. Gestational weight gain was divided into three categories: below Institute of Medicine (IOM) recommendations (<15 lbs), within IOM recommendations (15-25 lbs), and above IOM recommendations (>25 lbs). Categories of 10-lb increments were also evaluated. The primary outcomes were preeclampsia, cesarean section, macrosomia, low birth weight (LBW), and perinatal death. Adjusted relative risks and 95% confidence intervals (CI) were calculated using Mantel-Haenszel pooled estimator.

RESULTS

Compared to women who gained 15-25 lbs, women who gained <15 lbs were 0.8 (95% CI 0.6-1.0), 0.9 (0.8-1.0), 0.6 (0.5-0.8), and 1.7 (1.4-2.2) times as likely to have preeclampsia, cesarean section, macrosomia, and LBW, respectively. Conversely, women who gained >25 lbs were 1.7 (1.5-1.9), 1.3 (1.2-1.4), 2.1 (1.9-2.3), and 0.6 (0.5-0.7) times as likely to have preeclampsia, cesarean section, macrosomia, and LBW, respectively. The lowest risk of adverse outcomes was for women who gained in the 6-14 and 15-24 lb categories. There was no association between gestational weight gain and perinatal death.

CONCLUSIONS

Increasing gestational weight gain appears to decrease the risk of LBW but elevates the risks of preeclampsia, cesarean section, and macrosomia. Overweight women should gain within current IOM recommendations.

Maternal obesity at conception programs obesity in the offspring

Risk of obesity in adult life is subject to programming during gestation. To examine whether in utero exposure to maternal obesity increases the risk of obesity in offspring, we developed an overfeeding-based model of maternal obesity in rats utilizing intragastric feeding of diets via total enteral nutrition. Feeding liquid diets to adult female rats at 220 kcal/kg(3/4) per day (15% excess calories/day) compared with 187 kcal/kg(3/4) per day for 3 wk caused substantial increase in body weight gain, adiposity, serum insulin, leptin, and insulin resistance. Lean or obese female rats were mated with ad libitum AIN-93G-fed male rats. Exposure to obesity was ensured to be limited only to the maternal in utero environment by cross-fostering pups to lean dams having ad libitum access to AIN-93G diets throughout lactation. Numbers of pups, birth weight, and size were not affected by maternal obesity. Male offspring from each group were weaned at postnatal day (PND)21 to either AIN-93G diets or high-fat diets (45% fat calories). Body weights of offspring from obese dams did not differ from offspring of lean dams when fed AIN-93G diets through PND130. However, offspring from obese dams gained remarkably greater (P < 0.005) body weight and higher % body fat when fed a high-fat diet. Body composition was assessed by NMR, X-ray computerized tomography, and weights of adipose tissues. Adipose histomorphometry, insulin sensitivity, and food intake were also assessed in the offspring. Our data suggest that maternal obesity at conception leads to fetal programming of offspring, which could result in obesity in later life.

Neighborhood factors associated with physical activity and adequacy of weight gain during pregnancy

Healthy diet, physical activity, smoking, and adequate weight gain are all associated with maternal health and fetal growth during pregnancy. Neighborhood characteristics have been associated with poor maternal and child health outcomes, yet conceptualization of potential mechanisms are still needed. Unique information captured by neighborhood inventories, mostly conducted in northern US and Canadian urban areas, has been shown to reveal important aspects of the community environment that are not captured by the demographic quantities in census data. This study used data from the Pregnancy, Nutrition, and Infection (PIN) prospective cohort study to estimate the influences of individual-level and neighborhood-level characteristics on health behaviors and adequacy of weight gain during pregnancy. Women who participated in the PIN study and who resided in Raleigh, North Carolina and its surrounding suburbs were included (n = 703). Results from a neighborhood data collection inventory identified three social constructs, physical incivilities, territoriality, and social spaces, which were hypothesized to influence maternal health behaviors. The physical incivility scale was associated with decreased odds (adjusted OR = 0.74, 95%CI = 0.57, 0.98) in participating in vigorous leisure activity before pregnancy after controlling for several individual confounders, and a crude association for decreased odds of excessive weight gain (OR = 0.79, 95%CI = 0.64, 0.98). The social spaces scale was associated with decreased odds for inadequate (adjusted OR = 0.74, 95%CI = 0.56, 0.98) and excessive (adjusted OR = 0.69, 95%CI = 0.54, 0.98) gestational weight gain. The social spaces scale was also associated with decreased odds of living greater than 3 miles from a supermarket (adjusted OR = 0.03, 95%CI = 0.00, 0.27). Territoriality was not associated with any pregnancy-related health behavior. None of the neighborhood constructs were associated with smoking or diet quality. Physical incivilities and social spaces neighborhood characteristics may be important to measure to improve our understanding of the potential mechanisms through which neighborhood environments influence health.

Systematic review: Accuracy of body mass index in predicting pre-eclampsia: bivariate meta-analysis

OBJECTIVE

The objective of this study was to determine the accuracy of body mass index (BMI) (pre-pregnancy or at booking) in predicting pre-eclampsia and to explore its potential for clinical application.

DESIGN

Systematic review and bivariate meta-analysis.

SETTING

Medline, Embase, Cochrane Library, MEDION, manual searching of reference lists of review articles and eligible primary articles, and contact with experts.

POPULATION

Pregnant women at any level of risk in any healthcare setting.

METHODS

Reviewers independently selected studies and extracted data on study characteristics, quality, and accuracy. No language restrictions.

MAIN OUTCOME MEASURES

Pooled sensitivities and specificities (95% CI), a summary receiver operating characteristic curve, and corresponding likelihood ratios (LRs). The potential value of BMI was assessed by combining its predictive capacity for different prevalences of pre-eclampsia and the therapeutic effectiveness (relative risk 0.90) of aspirin.

RESULTS

A total of 36 studies, testing 1,699,073 pregnant women (60,584 women with pre-eclampsia), met the selection criteria. The median incidence of pre-eclampsia was 3.9% (interquartile range 1.4-6.8). The area under the curve was 0.64 with 93% of heterogeneity explained by threshold differences. Pooled estimates (95% CI) for all studies with a BMI > or = 25 were 47% (33-61) for sensitivity and 73% (64-83) for specificity; and 21% (12-31) and 92% (89-95) for a BMI > or = 35. Corresponding LRs (95% CI) were 1.7 (0.3-11.9) for BMI > or = 25 and 0.73 (0.22-2.45) for BMI < 25, and 2.7 (1.0-7.3) for BMI > or = 35 and 0.86 (0.68-1.07) for BMI < 35. The number needed to treat with aspirin to prevent one case of pre-eclampsia ranges from 714 (no testing, low-risk women) to 37 (BMI > or = 35, high-risk women).

CONCLUSIONS

BMI appears to be a fairly weak predictor for pre-eclampsia. Although BMI is virtually free of cost, noninvasive, and ubiquitously available, its usefulness as a stand-alone test for risk stratification must await formal cost-utility analysis. The findings of this review may serve as input for such analyses.

Managing Excessive Weight Gain During Pregnancy and the Postpartum Period

Childbearing is a period in the life cycle during which some women may gain weight, become overweight, or become obese. Despite guidelines issued in 1990 for gestational weight gain, many women exceed them. Women who are overweight before pregnancy are most vulnerable to excessive gestational weight gain. Prenatal interventions to prevent excessive gain have had mixed results. During the postpartum period, 14% to 20% of women may retain weight from pregnancy, which elevates risk of later health problems. Although postpartum weight loss interventions have been shown to have efficacy, these have been tested primarily with White women. Continued efforts are needed in practice and research to develop effective approaches for managing weight during pregnancy and postpartum, especially for low-income and ethnic minority women.

Caring for Obese Pregnant Women

Women who are overweight or obese during their childbearing years are at an increased risk for pregnancy-induced hypertension, gestational diabetes, labor induction, cesarean births, and failed vaginal birth after cesarean. During the postpartum, they experience increased rates of puerperal infection and decreased rates of breastfeeding initiation or continuation. Their infants are at higher risk for having congenital anomalies or being stillborn. Nurses can use this knowledge to adapt the care they provide and to encourage health-promoting behaviors.

Obesity and pregnancy complications

Maternal obesity increases the risk of numerous complications of pregnancy, labor, and birth for both mother and neonate, including diabetes and hypertensive disorders. As more women enter pregnancy with a body mass index (BMI) indicative of overweight or obesity, providers of obstetric care should be aware of the implications of this increased BMI on perinatal outcomes as well as become familiar with management options.

The implications of maternal overweight and obesity on the course of pregnancy and birth outcomes

The increasing prevalence of overweight and obesity among women of childbearing age is a growing public health concern in the United States. The average body mass index (BMI) is increasing among all age categories and women enter pregnancy at higher weights. Women are also more likely to retain gestational weight with each pregnancy. Women who are overweight (BMI 25–30) and obese (BMI ≥30) are at greater risk of adverse reproductive health outcomes compared to women of normal weight status (BMI 19.8–25). This article provides an overview of the complications associated with maternal overweight and obesity including diabetes, pre-eclampsia, c-sections, and birth defects. We present updated information on the weight trends among women. Finally, we present an overview of the prevention studies aimed at adolescents and women prior to pregnancy.

Trends in pre-pregnancy obesity in nine states, 1993-2003

OBJECTIVE

Pre-pregnancy obesity poses risks to both pregnant women and their infants. This study used a large population-based data source to examine trends, from 1993 through 2003, in the prevalence of pre-pregnancy obesity among women who delivered live infants.

RESEARCH METHODS AND PROCEDURES

Data from the Pregnancy Risk Assessment Monitoring System in nine states were analyzed for trends in pre-pregnancy obesity (BMI>29.0 kg/m2) overall and by maternal demographic and behavioral characteristics. Pre-pregnancy BMI was calculated from self-reported weight and height on questionnaires administered after delivery, and demographic characteristics were taken from linked birth certificates. The sample of 66,221 births was weighted to adjust for survey design, non-coverage, and non-response, and it is representative of all women delivering a live birth in each particular state. The sampled births represented 18.5% of all births in the United States.

RESULTS

Pre-pregnancy obesity increased 69.3% during the study period, from 13.0% in 1993 to 1994 to 22.0% in 2002 to 2003. The percentage increase ranged from 45% to 105% for individual states. Subgroups of women with the highest prevalence of obesity in 2002 to 2003 were those who were 20 to 29 years of age, black, had three or more children, had a high school education, enrolled in Women, Infants, and Children, or were non-smokers. However, all subgroups of women examined experienced at least a 43% increase in pre-pregnancy obesity over this time period.

DISCUSSION

The prevalence of pre-pregnancy obesity is increasing among women in these nine states, and this trend has important implications for all stages of reproductive health care.

Obesity and time to pregnancy

BACKGROUND

Obesity may reduce fecundity. We examined the obesity-fecundity association in relation to menstrual cycle regularity, parity, smoking habits and age to gain insight into mechanisms and susceptible subgroups.

METHODS

Data were provided by 7327 pregnant women enrolled in the Collaborative Perinatal Project at 12 study centres in the United States from 1959 to 1965. Prepregnancy body mass index (BMI) was analysed continuously and categorically [underweight (<18.5 kg/m2), optimal weight (18.5-24.9 kg/m2), overweight (25.0-29.9 kg/m2) and obese (>or=30.0 kg/m2)]. Adjusted fecundability odds ratios (FORs) were estimated using Cox proportional hazards modelling for discrete time data.

RESULTS

Fecundity was reduced for overweight [OR=0.92, 95% confidence interval (95% CI): 0.84, 1.01] and obese (OR=0.82, 95% CI: 0.72, 0.95) women compared with optimal weight women and was more evident for obese primiparous women (OR=0.66, 95% CI: 0.49, 0.89). Fecundity remained reduced for overweight and obese women with normal menstrual cycles. Neither smoking habits nor age modified the association.

CONCLUSIONS

Obesity was associated with reduced fecundity for all subgroups of women and persisted for women with regular cycles. Our results suggest that weight loss could increase fecundity for overweight and obese women, regardless of menstrual cycle regularity, parity, smoking habits and age.

Maternal birthplace and breastfeeding initiation among term and preterm infants: a statewide assessment for Massachusetts

OBJECTIVES

Among premature infants, formula feeding increases the risk for necrotizing enterocolitis, delayed brainstem maturation, decreased scoring on cognitive and developmental tests, and delayed visual development. With this in mind, many interventions are designed to increase breast milk consumption in preterm infants. Breastfeeding initiation rates among US premature infants are not collected nationally, however, and published data on breastfeeding rates in this population are limited. In addition, national surveys calculate breastfeeding rates among term infants according to maternal race/ethnicity, but maternal birthplace is not recorded. This is likely to be important, because breastfeeding is the cultural norm in the countries of origin for many non-US-born US residents. Massachusetts has a diverse racial/ethnic population, including many non-US-born women. The goals of this study were to compare breastfeeding initiation rates among preterm and term infants in Massachusetts in 2002 and to determine the effect of maternal race/ethnicity and birthplace on breastfeeding initiation rates among term and preterm infants.

METHODS

Massachusetts Community Health Information Profile, an online public health database that was created by the Massachusetts Department of Public Health, includes breastfeeding initiation data that are obtained from the electronic birth certificate, which we used to compare breastfeeding rates among preterm and term infants. Birth-linked demographics and data that also were accessed were maternal age, race/ethnicity, birthplace, and health insurance (public or private) as an indicator of socioeconomic status and infant's gestational age. We assessed the association between breastfeeding initiation and maternal birthplace, as well as race/ethnicity and the other potential confounders, using logistic regression.

RESULTS

There were 80,624 births in Massachusetts in 2002, and 8.2% (6611) of newborns had a gestational age <37 weeks. The state's overall breastfeeding initiation rate was 74.6%. We excluded records of mothers who were younger than 15 years and older than 39 years, nonsingleton births, infants with a gestational age <24 weeks and >42 weeks, and records with missing data. Of the total births in Massachusetts, 67,884 (84%) met inclusion criteria for this study. Breastfeeding initiation rates were lowest among preterm infants of the youngest gestational ages. Breastfeeding initiation was 76.8% among term infants born at 37 to 42 weeks, 70.1% among infants born at 32 to 36 weeks, and 62.9% among infants born at 24 to 31 weeks. In univariate analysis, among preterm infants, a lower proportion of US-born black, Asian, and Hispanic mothers initiated breastfeeding than US-born white mothers; non-US-born black and non-US-born Hispanic mothers had the highest breastfeeding initiation rates. Among term infants, US-born black mothers had the lowest initiation rates, and non-US-born black and non-US-born Hispanic mothers had the highest. In multivariate logistic regression, however, after controlling for mother's age, race, birthplace, and insurance, US-born white mothers were least likely to breastfeed either term or preterm infants when compared with any other racial/ethnic group, including US-born black mothers. The likelihood that non-US-born Hispanic mothers would breastfeed was almost 8 times greater than that for US-born white mothers for a preterm infant and almost 10 times greater for a term infant. In multivariate logistic regression analysis stratified by gestational age for both preterm and term infants, older mothers and mothers with private health insurance were most likely to breastfeed.

CONCLUSIONS

In Massachusetts, preterm infants were less likely to receive breast milk than term infants, and the likelihood of receiving breast milk was lowest among the youngest preterm infants. In multivariate logistic regression, mothers who were born outside the United States were more likely than US-born mothers to breastfeed either term or preterm infants in all racial and ethnic groups. In an unexpected finding, US-born white mothers were less likely to breastfeed term or preterm infants than US-born black mothers or mothers of any other racial or ethnic group.

Review article: Operating on the obese woman-a review

In this review the authors recognise the growing contribution of obesity to problems in obstetrics and gynaecology. They then focus on methods to reduce complications in intrapartum and gynaecological care particularly in relation to operating on the obese woman. Strategies to reduce surgical morbidity are discussed including consideration of the site of incision, asepsis and reduction in postoperative complications.