Introduction

Preeclampsia is a hypertensive disorder unique to pregnancy that occurs in 5–8 % of pregnancies in the United States [1–3]. The disease is classified as mild in 75 % of cases, and 10 % of cases occur before 34 weeks gestation [4]. Women who develop preeclampsia are at increased risk for development of seizures, pulmonary edema, coagulation defects, hepatic and/or renal failure, cerebral hemorrhage, blindness, and death [2, 5–8]. Preeclampsia also causes significant neonatal compromise. Women with preeclampsia are 3–4 times more likely to deliver a small-for-gestational age infant compared to healthy women [9]. Medically indicated preterm birth resulting from fetal or maternal complications is another serious issue [10]. In addition, women experiencing preeclampsia seem to be at an elevated risk for cardiovascular disease later in life [11, 12]. Currently, there are no proven measures to treat preeclampsia other than delivery.

Teenage pregnancy is associated with many adverse maternal and fetal outcomes including preterm birth, low birth weight, gestational diabetes mellitus and preeclampsia [13–15]. Increasing teenage pregnancy rates, adverse consequences associated with childbearing among teens, and morbidities associated with maternal obesity make this an important public health concern. However, data are lacking with respect to the specific maternal characteristics rendering this group as high risk. Consequently, our objective was to identify potentially modifiable risk factors for preeclampsia in a contemporary American teen population.

Materials and methods

We conducted a retrospective cohort analysis of all teenage deliveries at the Washington Hospital Center (Washington, DC) between 2000 and 2004. Approval from our Institutional Review Board was obtained prior to data collection. Inclusion criteria included nulliparity and maternal age of 18 years or less. Exclusion criteria included multiparity, unknown prepregnancy body mass index (BMI), delivery prior to 20 weeks gestation, and maternal age greater than 18 years.

All cases of preeclampsia were identified using the National Working Group on Research on Hypertension during Pregnancy [16]. The groups were further classified into mild or severe preeclampsia and early onset (<34 weeks) or late onset preeclampsia (≥34 weeks).

Demographic data were abstracted from the prenatal and inpatient records. Maternal age, race/ethnicity, height, and prepregnancy weight were self-reported. Maternal BMI was calculated from the patient’s reported height and prepregnancy weight. For analysis, the subjects were categorized into normal, overweight, obese groups as defined by the National Institutes of Health and the World Health Organization as follows: BMI <25.0 kg/m2 was considered to be normal weight, BMI between 25 and 29.9 kg/m2 were considered overweight, and BMI ≥30 kg/m2 were considered obese. The following data collected were also based on maternal self-report: smoking, illicit substance use, and date of last menstrual period. Gestational age was determined from prenatal records. In cases of uncertain last menstrual period, ultrasound determined gestational age was used. We defined sexually transmitted infection as diagnosis of Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis, or Treponema pallidum during the pregnancy.

With respect to weight gain in pregnancy, the total amount of gain in pregnancy was divided by the gestational age at delivery to obtain the per-week weight gain value. Then, using the 2009 Institute of Medicine (IOM) guidelines, the subjects were categorized based on whether they gained more than or the recommended amount of weight.

Adverse pregnancy outcomes of interest included gestational diabetes (using the Carpenter and Coustan diagnostic criteria) [17], oligohydramnios (amniotic fluid index <5 cm), and placental abruption (based on diagnosis by clinician). Intra and postpartum outcomes of interest included postpartum hemorrhage (based on diagnosis by clinician), clinical chorioamnionitis or endometritis (confirmed by review of inpatient records), non-reassuring fetal status (confirmed by review of inpatient records) and birth weight.

Data were analyzed using IBM SPSS Statistics software (version 19.0, SPSS, Inc., Chicago, IL) and were summarized using basic descriptive statistics. Analysis was performed using Fisher’s exact, student t test. All p values were two-tailed, with p < 0.05 considered statistically significant.

Results

Of the 10,322 deliveries during the study period, 730 (7.1 %) were to nulliparous teenage mothers with ages ranging from 11 to 18 years who met inclusion criteria. Of the 730 included teen deliveries, 65 (8.9 %) women were diagnosed with preeclampsia. There were 654 (90 %) black mothers, 73 (10 %) Hispanic mothers, and only three white mothers in the study population. Five hundred ninety-seven of 730 (82 %) had a BMI >25 kg/m2. Teenage mothers with preeclampsia had a significantly higher BMI (32.9 ± 8.4 vs. 30.3 ± 6.1, p = 0.002) and had higher gestational weight gain (35.3 ± 15.3 vs. 31.1 ± 14.5 pounds, p = 0.03) than those mothers without preeclampsia. All other maternal demographic data were similar among the groups (Table 1).

Table 1 Maternal demographics
Full size table

Adverse maternal–neonatal outcomes are presented in Table 2. Teenage mother with preeclampsia were more likely to have gestational diabetes mellitus and to experience postpartum hemorrhage.

Table 2 Maternal–neonatal outcomes
Full size table

Maternal obesity (BMI ≥30 kg/m2, RR 1.6, 95 % CI 1.0–2.8) and gestational weight gain above the IOM-recommended levels (RR 2.6, 95 % CI 1.5–4.4) were associated with higher risk for development of preeclampsia. When evaluating by severity or onset of disease, weight gain above IOM-recommended levels was associated with the development of mild (n = 58) or late onset (n = 54) preeclampsia (RR 2.5, 95 % CI 1.4–3.4) (Tables 3, 4). No association was noted between gestational weight gain and either severe or early onset preeclampsia.

Table 3 Evaluation of risk factors in early versus late onset preeclampsia
Full size table
Table 4 Evaluation of risk factors in mild versus severe preeclampsia
Full size table

Discussion

In this study, we sought to identify potentially modifiable risk factors for preeclampsia in a contemporary American teen population. In our predominantly black inner-city teenage cohort, higher prepregnancy BMI, especially obesity, and gestational weight gain above the IOM-recommended levels place the gravid teen at an elevated risk for development of preeclampsia. However, this association was strongest for mild and late onset preeclampsia. There was no association between gestational weight gain above the IOM-recommended levels and severe or early onset preeclampsia.

There has been sparse data to date investigating risk factors for preeclampsia in teenage mothers. Sukalich et al. [18] recently reported adverse pregnancy outcomes in 4,822 adolescent women. 28 % of the women studied had a BMI ≥25. Preeclampsia was more common in teenage mothers with a BMI ≥25 (OR 1.7, 95 % CI 1.4–2.3). The odds of preeclampsia increased in a graded fashion for overweight, obese, and morbidly obese women, respectively (OR 1.6, 1.9, 3.0). Our study is different in that we used a population that was predominantly black. While we found similar results for mild or late onset preeclampsia, there was no association between obesity and severe or early onset preeclampsia. That excessive weight gain in pregnancy and obesity seem to be risk factors for only the mild variant of this disorder provides further evidence that mild and severe preeclampsia may, at least in part, be pathophysiologically different.

Our study has some limitations which 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, which was a significant focal point in our analysis plan. In addition, parity may introduce other confounding that we cannot account for. Furthermore, our BMI calculations were based on self-reported prepregnancy weights, which could potentially impact our findings. However, reported weight is frequently underestimated in overweight females [19]. Consequently, the association we report between prepregnancy BMI and subsequent development of preeclampsia is most likely an underestimate of the true risk.

Despite these limitations, we conclude that maternal obesity and higher than IOM-recommended gestational weight gain place the gravid teen at increased risk for preeclampsia. The modifiable nature of these risk factors permits the possibility of intervention and prevention. The absence of obesity’s impact on early onset or severe preeclampsia in our cohort further supports a role for an underlying genetic predisposition in these women. Elucidating the different mechanisms involved in both variants of this disease may allow development of preventive and medical interventions for preeclampsia and its sequelae.