Being white, 20-34 years of age or a high school graduate was associated with receiving early prenatal care (in the first trimester of pregnancy) in a study of all Medicaid recipients giving birth in rural Williamsburg County, South Carolina, in 1994-1995.1 Early prenatal care was not associated with improved outcomes: Newborns of mothers not receiving such care had reduced odds of having a medical condition (odds ratio, 0.4-0.5). The authors note that given the current emphasis in health care on cost-effective service delivery, "the cost implications of infant morbidity make it an important public policy issue."

The researchers studied 558 births using data from birth certificates and state and hospital records. They looked primarily at whether the mothers' timing of prenatal care (in the first trimester or later) and background characteristics were associated with various birth outcomes—low birth weight (less than 2,500 g) and preterm delivery (before 37 weeks' gestation), which the authors note are "the primary determinants of infant morbidity"; infant morbidity (selected diagnoses at birth or medical problems within 30 days); hospital costs; and duration of hospital stay. The researchers used chi-square and Student t-tests and logistic regression to assess statistical significance.

Eighty-three percent of the mothers were nonwhite; virtually all of these women were black. In general, racial differences in the demographic makeup of the mothers were statistically significant. Half of white mothers (51%), compared with two-thirds of nonwhite mothers (66%), had completed high school. A significantly higher proportion of whites than of nonwhites were living with a spouse (43% vs. 10%). Among white mothers, 34% were younger than 20, and 66% were 20-34; among nonwhite mothers, 34% were younger than 20, 59% were 20-34 and 6% were older. However, comparable proportions of white and nonwhite mothers (43% and 45%) had had no previous births.

White and nonwhite women did not differ significantly in the proportions having preterm delivery (14% and 11%) or low-birth-weight infants (15% and 16%); however, infants of white mothers weighed more at birth, on average, than infants of nonwhite mothers did (3,232 g vs. 3,130 g).

Two-thirds of the women received early prenatal care (67%). Timing of the initiation of prenatal care varied according to race, age and education. Seventy-six percent of whites, compared with 65% of blacks, received first-trimester care; 70% of high school graduates, versus 61% of less-educated women, received such care. The age-group with the highest proportion of first-trimester care was 20-34-year-olds (73%), followed by women 35 or older (59%) and teenagers (58%). Three-quarters of women receiving early prenatal care (74%), and nearly two-thirds of those not receiving such care (65%), were living with a spouse; this difference was not statistically significant. The mean number of prenatal care visits differed between married and nonmarried mothers (12.5 vs. 10.6), as well as between white and black mothers (13.4 vs. 10.4).

Most newborns had no medical problems, regardless of whether their mothers received first-trimester care (84%) or not (93%). However, the proportion of newborns experiencing poor outcomes was significantly higher among those whose mothers received early prenatal care than among those whose mothers did not. Compared with infants whose mothers did not receive early prenatal care, infants whose mothers received first-trimester care had a higher prevalence of general morbidity (19% vs. 11%) and low birth weight (18% vs. 11%). On average, they also had longer hospital stays (4.3 vs. 2.7 days) and incurred higher hospital charges ($2,628 vs. $1,005).

In multivariate logistic regression analysis, two maternal characteristics, marital status and race, were independently associated with birth outcome. Nonmarried mothers' odds of preterm delivery were three times those of married mothers (odds ratio, 3.2), and their odds of high hospital costs were more than double those of married mothers (2.5). The odds of incurring high hospital charges were lower for nonwhite women than for white women (0.6). Women who had not begun prenatal care in the first trimester had reduced odds of having an infant with a medical problem (0.4-0.5).

The "most surprising finding" of this study, according to the authors, was the observation of poorer birth outcomes in women with early prenatal care than in those without first-trimester care. The authors believe this finding suggests that "high-risk mothers were appropriately identified and obtained earlier prenatal care." Moreover, they conclude that "adequate prenatal care is complex, involving more than simply assuring that mothers initiate prenatal care early in pregnancy."

The authors suggest that future studies examine several variables not included in their analyses. For example, details of the prenatal care services delivered (such as whether the woman received coordinated, enhanced services) and the mother's health characteristics (including nutritional status and the presence of multiple medical conditions) could be assessed for associations with birth outcomes.

--C. Coren

1. Guillory VJ et al., Prenatal care and infant birth outcomes among Medicaid recipients, Journal of Health Care for the Poor and Underserved, 2003, 14(2):272-289.