authored by Brittany N Robles*
Abstract
To analyse changes in Gestational Weight Gain (GWG) in different Body Mass Index (BMI) categories at start of pregnancy and neonatal birth weight outcomes in a predominantly Hispanic population living in a low-income environment.
We conducted a cross sectional study of women with singleton gestation who delivered at Wyckoff Heights Medical Centre from January 1st to December 31st, 2017. BMI was categorized at first prenatal visit as normal weight (BMI= 18.5-24.9), overweight (BMI= 25-29.9) and obese (BMI >30). BMI was collected at 16-20, 24-28, and 36-38 weeks of gestation. Stratified by BMI, appropriate GWG were 25–35 pounds for normal weight (27.9%), 15–25 pounds for overweight (34.5%), and 11–20 pounds for obese (24.5%). Neonatal birth weight was categorized by Duryea percentiles and gestational age in weeks. From 831 women, normal weight (n=269), overweight (n=263), and obese (n=299) women were found. GWG was categorized as: inadequate, appropriate, or excessive based on the Institute of Medicine guidelines. The prevalence of excessive GWG was 23.1% for normal weight, 35.8% for overweight, and 37.5% for obese women. The prevalence of inadequate GWG was 48.9% for normal weight, 31.0% for overweight, and 40.6% for obese women. A significant association was found between obese women and >90 percentile neonatal birth weight (OR:2.3, 95% CI: 1.15-4.97). Obese women were more likely to have excessive GWG which is associated with maternal and neonatal adverse outcomes such as NICU admissions, gestational diabetes, hypertensive disorders in pregnancy, delivery by caesarean section, large for gestational age, and shoulder dystocia.
Keywords: Gestational weight gain; Maternal obesity; Pregnancy weight gain; Pregnancy complications
Introduction
Gestational weight gain (GWG) is the amount of weight one gains throughout the pregnancy. This weight gain can be influenced by many factors including: age, socioeconomic factors, ethnicity, and maternal comorbidities, such as pre-gestational obesity [1-4]. Excessive gestational weight can lead to numerous adverse maternal and neonatal events such as the development of gestational diabetes, gestational hypertension, and preeclampsia, delivery via caesarean section, macrosomia, neonatal hypoglycaemia and shoulder dystocia. Due to the complications that can arise, recommendations were set forth by The Institute of Medicine (IOM) designating the appropriate amount of weight women should gain based on her pre-pregnancy BMI [5]. Although these guidelines were set forth just eleven years ago in 2009, they are debatable and do not take into consideration various important factors such as: weight gain among different ethnic groups, those of low socioeconomic status and/or those with a lower education level [5].
In the United States, more than 40% of pregnant women exceed the Institute of Medicines guidelines [6]. Excessive gestational weight gain varies by ethnicity and socioeconomic status with low income populations and non-whites being at the greatest risk [1].
Hispanics are the largest minority group living in the United States. They have the highest rates of inadequate and excessive GWG and are the group with the highest birth rate [6]. Hispanic women, specifically those from the Caribbean, experience the greatest health disparity. Furthermore, this subgroup of women has the highest prevalence of maternal comorbidities including obesity and type 2 diabetes mellitus and exhibit adverse outcomes associated with poor nutrition [6].
Women who are classified as severely obese at conception have an increased risk of infant mortality, stillbirth, congenital malformations, large for gestation infants, hypertensive disorders of pregnancy, gestational diabetes, prolonged second stage of delivery, delivery via caesarean section and maternal mortality than non-obese women [7].
In our predominantly Hispanic population, we sought to determine whether the pattern of maternal gestational weight gain was associated with clinically significant changes in the neonatal birth weight.
Materials and Methods
Design and settings
We performed a single‐centre, retrospective study of patients enrolled in the prenatal service and delivered at Wyckoff Heights Medical Centre in Brooklyn, New York. The hospital is located in a community comprised of primarily Latinos living below the poverty line [8]. We enrolled women who received prenatal care and delivered a live born singleton gestation presenting to the obstetrics and gynaecology department between January 1st to December 31st, 2017 and delivered a singleton infant. This study was approved by our Institutional Review Board at Wyckoff Heights Medical Centre.
Study population
We enrolled a sample of adult women, 18 years or older, who received prenatal care and delivered at Wyckoff Heights Medical Centre. One thousand three hundred fifty-six charts were reviewed and eight hundred forty-five women met the inclusion criteria. Fourteen women who were classified as underweight at the initial prenatal visit were excluded due to inadequate sample size.
Data collection and data management
Baseline demographic data were collected on all enrolled women and neonates (Table 1). Maternal data such as maternal age at delivery, height, body weight at: first prenatal visit, 16-20 weeks’ gestation, 24-28 weeks’ gestation, 36-38 weeks’ gestation, as well as reproductive characteristics such as gravidity, parity, mode of delivery, past medical history and blood which were extracted from the hospital medical record. Neonatal data including gestational age at delivery, birth weight, and neonatal intensive care unit admission (Figure 2) as well as length of stay were collected from the hospital medical record.
Gestational age was calculated from the first day of the last menstrual period which was confirmed by ultrasound, or from the first dating ultrasound scan performed if the last menstrual period was unknown [9].
We conducted analyses of birth weight based on gestational age. Large for gestational age (LGA) and small for gestational age (SGA) were based on the 90th and 10th percentiles of weight for gestational age, respectively, based on the Duryea birth weight chart [10].
Measurements
Body mass index was calculated as the woman’s first documented pregnancy weight in kilograms divided by height in squared meters. Based on BMI, women were classified as normal weight (18.5–24.9 kg/m2), overweight (25.0 to 29.9 kg/m2) or obese (≥30 kg/m2). According to the 2009 IOM GWG recommendations, patients who are normal weight should gain 25-35lbs with an average weight gain of 1lb per week in the second and third trimester [11]. Patients categorized as overweight, should gain 15-25lbs with an average weight gain of 0.6lbs per week in the second and third trimester, and lastly patients categorized as obese, should gain 11-20lbs with an average weight gain of 0.5lbs per week in the second and third trimester [11].
Gestational weight gain was calculated by subtracting the pregnancy weight measured at the first prenatal visit from the weight recorded at the 36-38-week visit. This gestational weight gain was then compared with the IOM recommended GWG for each BMI category and categorized as inadequate, adequate or excessive. Specifically, adequate GWG was defined as weight gain of 25 to 35 pounds for women of normal BMI, 15 to 25 pounds was for overweight women and 11 to 20 pounds for obese women. Inadequate and excessive GWG were defined as less and more than adequate GWG according to the IOM guidelines, respectively. Gestational weight gain and body mass index were also examined with respect to other sociodemographic and health determinants. Ethnicity was self-reported by different ethnic categories such as: Caucasian, Hispanic, Asian, African American, or Other.
Statistical analysis
Statistical analyses were performed using STATA software package (STATA version 15.1, College Station, Texas). We used Wald chi-square tests to identify statistically significant differences of women gaining inadequate, adequate or excessive weight in each category. We examined associations between characteristics of interest and gestational weight gain adequacy using multinomial logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI). Statistical significance was claimed at P < 0.05.
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