Neonatal death risk: effect of prenatal care is most evident after term birth. (Digests).

Women in the United States who do not receive prenatal care have an increased risk of experiencing a neonatal death, especially if they deliver at or after 36 weeks' gestation, according to findings from a large population-based cohort study. (1) Lack of prenatal care is associated with a 40% increase in the risk of neonatal death overall and a doubling of the risk among women delivering at or after 36 weeks' gestation. Black women are more than three times as likely as white women not to receive prenatal care, and regardless of their prenatal care status, their infants are significantly more likely to die within their first 27 days of life than are infants born to white women.

To examine the association between prenatal care and neonatal deaths (those occurring within the first 27 days of life), researchers analyzed perinatal mortality data for 1995-1997 collected by the National Center for Health Statistics. During that time, there were nearly 12 million pregnancies in the United States. The researchers restricted their sample to live singleton births that occurred at 24 weeks' gestation or later. They excluded births of infants who had congenital or chromosomal abnormalities, or who weighed less than 500 g at delivery, and births with missing data on gestational age or mother's receipt of prenatal care (defined as at least one visit during pregnancy). After the exclusions, the sample consisted of 10.5 million births, among which there were 18,339 neonatal deaths and 118,721 mothers who had not received prenatal care.

The researchers used multivariate logistic regression analysis to determine the association between prenatal care and neonatal death. The analyses were adjusted for maternal age, education and parity; smoking and alcohol use during pregnancy; gestational age; birth weight; and prenatal high-risk conditions (maternal anemia, intrapartum fever, preterm premature rupture of the membranes, excess amniotic fluid, diabetes, chronic hypertension, pregnancy-induced hypertension, renal disease, premature detachment of the placenta, placenta previa, bleeding of unknown cause, fetal growth restriction, Rh sensitization, postterm pregnancy and history of delivering a preterm or small-for-gestational-age infant).

About 1% of all women had received no prenatal care; the overall neonatal death rate was 1.7 per 1,000 births. In analyses by race, black mothers were more than three times as likely as white mothers not to have received prenatal care (2.7% vs. 0.8%). In addition, neonatal death rates were higher among black infants than among white infants, regardless of prenatal care status (2.7 vs. 1.5 per 1,000 births for infants whose mothers had prenatal care; 10.7 vs. 7.9 per 1,000 births for those whose mothers had none).

In multivariate analyses, women who did not have prenatal care were 40% more likely than those who did to experience a neonatal death (relative risk, 1.4). The risk of neonatal death among infants born to women with and without prenatal care was affected by gestational age: Infants born at 24-35 weeks' gestation to mothers without prenatal care were 20% more likely than those born to mothers with care to die within their first 27 days of life; among infants born at or after 36 weeks' gestation, the relative risk of neonatal death was 2.1 among those born to mothers without care. Lack of prenatal care incased the relative risk of neonatal death 40% among infants born to black women and 50% among those born to white women. For black and white women combined, not having prenatal care was significantly associated with an increased risk of neonatal death by preterm premature rupture of the membranes, placenta previa and fetal growth restriction (1.3-1.9).

In light of their findings that among infants born to women without prenatal care, those born at or after term had a greater risk of neonatal death than those born preterm, the researchers propose that the "phenomenon is possibly related to the fact that prematurity per se is the major determinant of neonatal deaths for infants born earlier than 36 weeks of gestation, thus making the benefits of prenatal care ... more evident at term." They also suggest that overestimation of gestational age may have been a factor.

The researchers comment that lack of prenatal care, unlike most factors associated with perinatal death, is "theoretically preventable." They suggest that more work needs to be done to determine why the association between perinatal death and lack of prenatal care occurs. Furthermore, the researchers note that the disparity in neonatal deaths between blacks and whites persisted even among those with prenatal care. They conclude that "more comprehensive strategies" than just prenatal care are needed to reach equity.

REFERENCE

(1.) Vintzileos AM et al., The impact of prenatal care on neonatal deaths in the presence and absence of antenatal high-risk conditions, American Journal of Obstetrics and Gynecology, 2002, 186(5):1011-1016.