Maternal age and birth outcomes: data from New Jersey

Abstract

The effects of maternal age on low birth weight, newborns' hospital costs and infant mortality were estimated based on individual 1989 and 1990 vital statistics records from New Jersey that were linked with uniform billing hospital discharge records. Results of multivariate analyses show a U-shaped relationship between maternal age and low birth weight among whites, with the youngest (younger than 15) and oldest (aged 40 and older) mothers being at higher risk than 25-29-year-olds; older teenagers were not at any significantly increased risk. Among blacks, however, 15-19-year-olds faced significantly lower risks of delivering low-birth-weight babies than did black women aged 25-29. Both black and white mothers in their 30s were significantly more likely to deliver a low-birth-weight baby than women aged 25-29 of the same race. The multivariate analysis also showed that newborn hospitalization costs increased with maternal age among both blacks and whites. The seemingly poorer birth outcomes of teenage mothers appear to result largely from their adverse socioeconomic circumstances, not from young maternal age per se.

PIP: This study compared birth outcomes among Black and White adolescents aged under 15 years, 15-17 years, and 18-19 years, in New Jersey. Data were obtained from vital statistics records for 1989 and 1990, and hospital discharge records from the New Jersey Department of Health. Hospital discharge records included insurance status and newborn costs. Adolescent data was compared to data among women aged 20-40 years. The 3 models run separately for each race were ones that allowed for the gross effects of age, controls for medical and behavioral risk factors only, and controls for socioeconomic status. Birth outcomes included infant mortality, low birth weight (LBW), and newborn costs. Findings indicate a complex set of relationships between maternal age, comparison groups, birth outcomes, and mediating factors. The analysis among White adolescents supports the common perception that teenage mothers are at higher risk of unfavorable birth outcomes and higher hospital costs than women in their 20s, but not all older women. Teenagers aged under 15 years had the highest risk of delivering a LBW infant compared to women aged 15-19 years, followed by mothers aged 40 years and older and women aged 35-39 years. Newborn costs among White and Black teenagers were lower than costs to older women. One caveat is that many teenagers are not at any increased risk of adverse birth outcomes, and unobserved determinants of adverse outcome could be related to prenatal care, smoking, or alcohol use. Black teenagers had a significantly reduced risk of having an LBW compared to 25-29 year olds. Poorer outcomes are attributed to adverse socioeconomic conditions. White teenagers aged under 15 years had the most unexplained risk. Risk of infant mortality increased with the increasing age of the mother, particularly among Black women. Rates of LBW among Black women aged 15-19 years were 3 times higher than among Whites.