High gestational weight gain does not improve birth weight in a cohort of African American adolescents.

BACKGROUND: Because pregnant African American women and teens are at risk of low birth weight, they are frequently counseled to strive for gestational weight gains at the upper limits of the Institute of Medicine's recommended ranges. OBJECTIVE: The objective was to examine whether such weight gains improve birth outcomes in a cohort of disadvantaged African American adolescents of low (<19.8), average (> or =19.8 to < or =26.0), or high (>26) prepregnancy body mass index (BMI; in kg/m2). DESIGN: Data were extracted from the medical charts of 1120 African American adolescents who received prenatal care at an inner-city maternity clinic between 1990 and 2000 and analyzed by using analysis of covariance and multivariate regression methods. RESULTS: Data were available for 815 adolescents, 711 of whom delivered at term (> or =37 wk). Fifty-eight percent (n = 409) of all term deliveries and 74% of the high-BMI adolescents (n = 126) had gains in the upper half of or above the recommended ranges. For all BMI groups, the most significant differences in birth outcomes were found in comparisons of teens who gained below the recommended ranges with those who gained in the lower half of the recommendation range. Further gains were not clearly beneficial, particularly for infants of high-BMI mothers. CONCLUSIONS: African American adolescents entering pregnancy underweight or at average weight should be counseled to gain within the recommended ranges, whereas overweight adolescents need support to avoid excessive gestational weight gain. Such advice would be prudent in light of the known associations between obesity and the increased likelihood of chronic diseases.

Calcium absorption is significantly higher in adolescents during pregnancy than in the early postpartum period.

BACKGROUND: Early childbearing may limit skeletal consolidation and increase calcium demands in adolescents. OBJECTIVE: The purpose of this study was to characterize calcium absorption in pregnant and lactating adolescents. DESIGN: Fractional calcium absorption was evaluated in 23 adolescents (mean +/- SD age: 16.5 +/- 1.4 y) during the third trimester of pregnancy (34.7 +/- 1.0 wk gestation) and again in 15 of these adolescents 31 +/- 8 d after delivery. Eight adolescents were breastfeeding their infants during the follow-up study. Fractional calcium absorption was determined by using oral ((46)Ca or (44)Ca) and intravenous ((42)Ca) stable calcium isotopes. Total-body and lumbar spine bone mineral density were measured in adolescents during the postpartum period by using dual-energy X-ray absorptiometry. RESULTS: Fractional calcium absorption was significantly greater during pregnancy than at 3-4 wk postpartum [0.526 +/- 0.152 (n = 23) compared with 0.297 +/- 0.108 (n = 15); P < 0.0001]. Lumbar spine z scores measured 19-44 d after delivery (n = 15) were significantly associated with calcium intake during pregnancy (y = -3.53 + 0.107x; R(2) = 0.355, P < 0.02) and were inversely related to fractional calcium absorption during pregnancy (y = 3.489 - 6.66x; R(2) = 0.52, P = 0.002). A total of 33% (5/15) of adolescents had lumbar spine z scores that met the definition of osteopenia (n = 3) or osteoporosis (n = 2) in the early postpartum period. CONCLUSIONS: Calcium absorption in adolescents was significantly higher during the third trimester of pregnancy than in the early postpartum period, and higher calcium intakes during pregnancy appeared to be protective against loss of trabecular bone at the lumbar spine.

Fetal femur length is influenced by maternal dairy intake in pregnant African American adolescents.

BACKGROUND: Pregnant adolescents may compete with their developing fetuses for the nutrients required for optimal bone mineralization. OBJECTIVE: The objective of this study was to determine the effect in pregnant African American adolescents of maternal dairy intake at entry into prenatal care on fetal femur development between 20 and 34 wk of gestation. DESIGN: A 10-y retrospective chart review was carried out in 1120 pregnant African American adolescents ( 3 servings/d), and a dose-response relation was suggested in the intermediate dairy-intake group (2-3 servings/d; P = 0.089). CONCLUSION: These data suggest that consumption of < 2 servings of dairy products/d by pregnant adolescents may negatively affect fetal bone development by limiting the amount of calcium provided to the fetus.

Vitamin D insufficiency is prevalent among pregnant African American adolescents.

STUDY OBJECTIVE: Recent attention has focused on vitamin D insufficiency but few data exist on vitamin D status among pregnant minority youth. DESIGN: A screening study was undertaken in adolescents having prenatal blood samples drawn for other routine tests obtained during the second trimester (18+/-1.8 week gestation, n=44) or third trimester of pregnancy (28.4+/-2.1 week gestation, n=36). Serum 25- hydroxyvitamin D (25(OH)D) was measured and significant determinants of vitamin D insufficiency in this cohort were identified. SETTING: Urban prenatal clinic. PARTICIPANTS: Eighty pregnant African American adolescents (< or = 18 y of age). MAIN OUTCOME MEASURE(S): Vitamin D status, STDs, hemoglobin, season, birth weight RESULTS: Serum 25(OH)D in this group averaged 21.6+/-8 ng/mL (age 16.5+/-1.1 y, n=80), and did not significantly differ between the second (20.95+/-8.2 ng/mL, n=44) and third trimester cohorts (22.5+/-7.9 ng/mL, n=36). Vitamin D insufficiency (< 20 ng/mL) was evident in 46.25% and vitamin D deficiency (<15 ng/mL) was evident in 21.25% of those studied. Significant predictors of suboptimal vitamin D status included sampling during the winter months (P=0.004), lower hemoglobin concentration (P=0.019), and higher second trimester leptin levels (P=0.018). Inverse associations between 25(OH)D and bacterial vaginosis were evident when controlled for season of sampling (P=0.02, n=80). CONCLUSIONS: Vitamin D insufficiency was prevalent among urban pregnant minority adolescents. Further studies are needed to address the impact of this finding on maternal and neonatal calcium homeostasis and bone health.

Iron deficiency anemia and depleted body iron reserves are prevalent among pregnant African-American adolescents.

Anemia is prevalent among pregnant adolescents, but few data exist on biochemical indicators of iron status in this group. We hypothesized that among an at-risk population of African-American, pregnant adolescents, the degree of iron depletion and deficiency would be marked, and that iron deficiency anemia would comprise the majority of the observed anemia. To examine this, blood samples were collected from 80 girls (< or =18 y old) attending an inner city maternity clinic, 23 of whom were studied longitudinally in the 2nd and 3rd trimesters depending on contact at the clinic. Sample sizes for the biomarkers varied according to the blood volume available at the time the assays were completed. Descriptive statistics were applied to characterize iron status, and multivariate regression and logistic analyses were used to identify significant determinants of iron status. Depleted iron stores (ferritin < or = 15 microg/L) were indicated for 25% (n = 44) and 61% (n = 59) of adolescents during the 2nd and 3rd trimesters, respectively. Serum folate (39.3 +/- 15.4 nmol/L, n = 60), RBC folate (2378 +/- 971 nmol/L, n = 60), and serum vitamin B-12 concentrations (313 +/- 163 pmol/L, n = 60) were within normal ranges. Adolescents with serum transferrin receptor:serum ferritin ratios (R:F ratio) > 300 during the 2nd trimester were 12.5 times (95% CI 2.83, 55.25) more likely to be classified with iron deficiency anemia during the 3rd trimester (P = 0.0002) than those with lower ratios. Estimates of body iron were lower in those tested after wk 26 of gestation (P < 0.0001), and reserves were depleted in 5.0% vs. 31.3% of the 2nd (n = 40) and 3rd (n = 48) trimester cohorts, respectively. In conclusion, iron-deficiency anemia was prevalent among these pregnant minority adolescents. Targeted screening and interventions to improve diet and compliance with prenatal iron supplementation are warranted for this at-risk group.

Hemoglobin concentrations influence birth outcomes in pregnant African-American adolescents.

Relationships between hemoglobin concentrations and birth outcomes have not been well characterized in African-American adolescents despite the fact that this group is at a higher risk of early childbearing. To address this issue, we characterized the prevalence of anemia and maternal factors associated with anemia in pregnant African-American adolescents. A retrospective medical chart review was undertaken of 918 adolescents who had received prenatal care at an inner-city maternity clinic between 1990 and 2000. Multiple log-linear regression analyses were used to address relationships between hemoglobin and adverse birth outcomes. The prevalence of anemia during the third trimester averaged 57-66% and was substantially higher than typically reported in adolescent and adult women. Multiparity, inadequate prenatal care, low prepregnancy BMI, history of self-reported cigarette use and infection with sexually transmitted diseases were significantly associated with lower hemoglobin during pregnancy. Adolescents with pre-eclampsia had higher hemoglobin (P < 0.01). Compared with the reference group (106-120 g/L), high hemoglobin (>120 g/L) during the second and third trimester significantly increased the risk of low birth weight (risk ratio (RR) = 3.11; [CI] 1.35, 7.13), and in the second-trimester cohort only, high hemoglobin concentrations increased the risk of preterm delivery (RR = 2.33; [CI] 1.07, 5.05). A U-shaped distribution between hemoglobin concentration and adverse birth outcomes was found in the third-trimester cohort when the reference range was decreased to 96-105 g/L to adjust for potentially lower hemoglobin concentrations among the African-American population. Our results suggest that additional medical attention may be warranted in pregnant African-American adolescents with hemoglobin concentrations of 120 g/L.

Characteristics and risk factors for adverse birth outcomes in pregnant black adolescents.

OBJECTIVES: To describe maternal characteristics and birth outcomes in a group of pregnant minority adolescents and to characterize the impact of maternal age (<15 years versus 15-17 years) on birth outcomes. STUDY DESIGN: A 10-year retrospective chart review was conducted in 1120 pregnant black adolescents (< or =17 years of age) who had received prenatal care at an inner-city maternity clinic in Baltimore, Md. RESULTS: Pregnant black adolescents had a higher incidence of low birth weight infants, preterm delivery, and fetal death compared with normative data from the United States. Younger adolescents were more likely to have inadequate utilization of prenatal care (P<.01). Older adolescents had a higher incidence of gonorrhea infections (P=.046), greater rates of self-reported substance abuse (P=.063), and a higher history of cigarette smoking (P<.01). Low prepregnancy body mass index (BMI), inadequate weight gain, and poor prenatal care utilization were strong independent predictors of preterm birth (P<.05). Low prepregnancy BMI, inadequate weight gain, female infant, and self-reported cigarette smoking history were significantly associated with decreased infant birth weight (P<.05). CONCLUSIONS: Pregnant black adolescents had increased risks of adverse pregnancy outcomes. This population should be studied further to develop age-appropriate and population-specific interventions to improve birth outcomes.