Obesity has become one of the most important public health problems in the United States, with one third of adolescents classified as either overweight or obese.1 Obesity is also associated with adverse pregnancy outcomes, including stillbirth, gestational diabetes, preeclampsia, and increased cesarean delivery rates.2,3
Teenage pregnancy is associated with adverse maternal and fetal outcomes including poor weight gain, low birth weight, prematurity, preeclampsia, and anemia.4–6 Potential adverse consequences associated with childbearing among teens, increasing teenage pregnancy rates, and morbidities associated with maternal obesity, make this an important public health concern.
Sukalich and colleagues7 reported a correlation between teenage obesity and adverse pregnancy outcomes such as increased rates of cesarean delivery, preeclampsia, and gestational diabetes. However, the majority of this study population was white. Previous research has shown racial differences in obesity rates and perinatal outcomes, including higher rates of maternal obesity, preterm birth, and cesarean delivery among African Americans.8–10 Taking into account the impact of race on pregnancy outcomes, our goal was to examine the relationship between obesity and pregnancy outcomes in our predominantly African-American inner-city teenaged population.
MATERIALS AND METHODS
We conducted a retrospective cohort analysis of all teenage deliveries the Washington Hospital Center from January 2000 through January 2004. Approval from our institutional review board was obtained before data collection. Maternal age, race/ethnicity, height, and prepregnancy weight were self reported. Inclusion criteria included nulliparity and maternal age of 18 years or less. Exclusion criteria included multiparity, unknown prepregnancy body mass index (BMI), delivery before 20 weeks of gestation, and maternal age greater than 18 years.
Maternal BMI was calculated from the patient’s reported height and prepregnancy weight. Patients were categorized into normal, overweight, obese groups as defined by the National Institutes of Health and the World Health Organization as follows: BMI less than 25.0 kg/m2 was considered normal weight (reference group), BMI between 25 and 29.9 kg/m2 was considered overweight (overweight group), and BMI greater than or equal to 30 kg/m2 was considered obese (obese group).
Demographic data were abstracted from the prenatal and inpatient records. The following data collected were also based on maternal self-report: prepregnancy weight, smoking, illicit substance use, and date of last menstrual period. Gestational age was determined from prenatal records. In cases of uncertain last menstrual period, ultrasonography determined gestational age was used. We defined sexually transmitted disease as diagnosis of Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis, or Treponema pallidum during the pregnancy. Adverse pregnancy outcomes of interest included preterm birth, defined as delivery before 37 or 34 weeks of gestation; gestational hypertension and preeclampsia, as defined by National Working Group for Hypertension in Pregnancy Guidelines; and gestational diabetes treated by oral hypoglycemic agent or insulin. Intrapartum and postpartum outcomes of interest included postpartum hemorrhage (based on diagnosis by clinician), clinical chorioamnionitis or endometritis (confirmed by review of inpatient records), small for gestational age (less than 10th percentile) and low birth weight (less than 2,500 grams).
Data were analyzed using SAS 9.1 software (SAS Institute, Inc., Cary, NC). The χ2 and Fisher exact test were used for analysis of categorical variables; analysis of variance (ANOVA) and the Dunnett test were used to compare group means. Multivariable logistic regression was used to determine the association of higher-BMI groups with gestational diabetes, preterm birth, cesarean delivery, and term low birth weight while adjusting for covariates (Table 1). Odds ratios (ORs) with 95% confidence intervals (CIs) were obtained for statistically significant outcomes. A P value less than 0.05 was considered statistically significant.
Of the 10,322 deliveries occurred during the study period, 712 (7%) were to teenaged mothers. Four hundred fifty-eight teenage deliveries met study inclusion criteria, with ages ranging from 11 to 18 years. Eleven (2%) patients were underweight and excluded from analysis. There were 405 (88%) African-American mothers, 52 (7%) Hispanic mothers, and 1 (0.002%) white mother in the study population. Two hundred seventy four (60%) of 458 had BMI less than 25 kg/m2; 106 (23%) were overweight, and 78 (17%) were obese. Maternal demographic data were similar among the groups, except for a higher proportion of African Americans in the obese group (88% compared with 95%, P<.03). The overweight and obese teens had a lower mean pregnancy weight gain when compared with the normal-weight mothers (30 and 29 compared with 32 lbs, P<.03, Table 2).
Gestational diabetes was more common in the obese teenagers (adjusted OR 4.2, 95% CI 1.5–12.1), as was cesarean delivery (adjusted OR 4.3, 95% CI 2.4–7.6). Lower incidence of spontaneous preterm birth before 37 (6% compared with 14%) and 34 (3% compared with 7%) weeks of gestation was seen in the obese teenagers; however, only the former reached statistical significance. Overweight maternal status rendered a higher risk of cesarean delivery (adjusted OR 1.8, 95% CI 1.0–3.0), while protecting against spontaneous preterm birth before 37 (adjusted OR 0.28, 95% CI 0.10–0.77), and 34 (adjusted OR 0.11, 95% CI 0.01–0.80) weeks of gestation. Induction of labor, or postpartum complications, such as fever, did not differ significantly between the groups (Tables 1 and 3).
Overweight teens had lower odds for delivery of a low birth weight infant at term (adjusted OR 0.19, 95% CI 0.04–0.86, Table 1). Although obese teens also had decreased odds for delivery of a low birth weight infant, this association was not statistically significant. Other neonatal outcomes, including macrosomia and nonreassuring fetal status, were not significantly different among groups (Table 4).
In our teenaged cohort, we found that maternal obesity is associated with adverse pregnancy outcomes, including gestational diabetes and cesarean delivery. Although studies have linked teenage maternal obesity to higher maternal–fetal morbidity, the data are sparse with respect to African-American, inner-city pregnant teenagers.7 Previous research has shown racial differences in maternal obesity and perinatal outcomes. African Americans are more likely to have a higher BMI when compared with white and are at higher risk for adverse outcomes, such as preterm birth and cesarean delivery.8–10 Considering these observations, we decided to examine the relationship between obesity and perinatal outcomes in our predominantly African-American teenaged population.
Similar to previously published findings in adult mothers, increased maternal weight in adolescents is associated with higher incidence of gestational diabetes and cesarean delivery.7 The high incidence of cesarean delivery is worrisome in this young population given the higher potential for postoperative complications, such as wound breakdown and infection. Further worrisome is the potential for future abdominal surgeries and associated morbidities, such as abnormal placentation, damage to intraabdominal organs, and the inherent difficulties of operating on an obese patient.
Similar to the findings by Sukalich et al,7 we demonstrated that obesity renders a protective effect on preterm birth. This is intriguing considering the higher baseline rate of preterm birth in African Americans and existing research suggesting an association between obesity and preterm birth.11,12 As demonstrated by Sabire,13 we believe that the association between higher BMI and preterm birth is due to obesity related comorbidities, rather than an inherent predilection to preterm birth. The young age of our patients, coupled with the relative paucity of obesity-related medical and obstetric complications, likely led to a more direct examination of the relationship between higher BMI and preterm birth.
Our study did not demonstrate a significant increase in the incidence of preeclampsia, as reported by Sukalich et al.7 This could be a reflection of the higher baseline rates of hypertensive disease in our African-American population or different potential confounders not measured.
Our study has some limitations that merit discussion. This study was retrospective in design and relied on chart review to establish diagnoses. It is possible that some diagnoses were over- or under-diagnosed, which has the potential to bias our results. We used multiparity as an exclusion criterion because parity is a risk factor for obesity due to retained pregnancy weight. In addition, parity may introduce other confounders that we cannot account for. Furthermore, our BMI calculations were based on self-reported prepregnancy weights, which could potentially impact our findings. However, as described by Rowland,14 reported weight is often underestimated in overweight females. Considering this fact, true weight estimate would likely lead to higher BMI values and, in fact, overestimate the increased risks we report in this study. We must caution that our aim was not to examine the effect of race on perinatal outcomes, but rather, the effect of obesity on pregnancy outcomes in a largely African-American population as we felt it would be more reflective of many inner-city settings.
Despite these limitations, we conclude that overweight and obese teenaged mothers are at increased risk for adverse perinatal outcomes. Given the risks of maternal overweight/obese status, targeted interventions to reduce teenage obesity should also be studied. Although historically the concern with teen pregnancies has been low birth weight, poor weight gain, and poor nutrition, the increasing rates of teen pregnancy and obesity warrant a change in our focus to include risks associated specifically with obesity.
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