Influence of the Adequacy of the Prenatal Care Utilization Index on Small-For-Gestational-Age Infants and Preterm Births in the United States.

Little is known about the associations of Adequacy of Prenatal Care Utilization (APNCU) index with small-for-gestational-age (SGA) infants and preterm births. This study investigated the association between the Adequacy of Prenatal Care Utilization (APNCU) index in relation to small-for-gestational-age (SGA) infants and preterm births. We used data from 212,050 pregnant women from the Pregnancy Risk Assessment Monitoring System (PRAMS) between 2004 and 2011. Multivariable logistic regression analyses were performed to examine the effect of the APNCU index on SGA infants and preterm births after controlling for maternal sociodemographic factors. Women who received adequate-plus prenatal care in reference to adequate prenatal care had increased odds for delivering SGA infants (adjusted odds ratio (AOR) = 1.08, 95% confidence interval (CI) = 1.03-1.15). Women with 9-11 prenatal care visits had increased odds of delivering SGA infants (AOR = 1.07, 95% CI = 1.02-1.14) compared to those with more than 12 visits. Among the four APNCU index categories, the highest rate of preterm births was observed in the adequate-plus group. Compared to those with adequate prenatal care, women who received adequate-plus prenatal care had increased odds of preterm birth (AOR = 1.69, 95% CI = 1.55-1.84). Compared to those with more than 12 visits, women with fewer than eight prenatal care visits had increased odds of preterm birth (AOR = 1.29, 95% CI = 1.13-1.48). In conclusion, women in the adequate-plus APNCU index category were more likely to deliver SGA infants and to have preterm births compared to those in the adequate APNCU index category. Women in the U.S. with high-risk pregnancies were prone to receiving adequate-plus prenatal care. Future prospective studies are warranted to investigate the influence of APNCU index in relation to pregnancy and birth outcomes.