Comparison of Three Prenatal Care Indices and their Association with Small for Gestational Age

1. Comparison of Three Prenatal Care Indices and their Association with Small for Gestational Age LaJeana Howie, MPH, CHES Kenneth Schoendorf, MD, MPH Centers for Disease Control and Prevention

2. Background • Prenatal care is a frequently used health service and is viewed as advantageous to pregnant women and their infants • Designed to identify women at risk of pregnancy complications and reduce adverse outcomes • Adequate prenatal care may be associated with reduced risk: • Preterm birth • Low birth weight • Fetal growth restriction

3. Small for Gestational Age (SGA) • Measure of fetal growth restriction, defined as less than the 10th percentile for gestational age • SGA has been associated with adverse health outcomes in infancy, childhood, and adulthood

4. Measures of Prenatal Care • Analysis of vital statistics data • Created from: • Timing of initial prenatal care visit • Number of visits • Gestational age at time of birth

5. Research Objective • To compare the associations between three common measures of prenatal care utilization with small for gestational age (SGA).

6. Data Source • 2000 U.S. Natality file • Singleton births • delivered between 37 and 42 weeks of gestation • Exclusions • Records missing information on birth weight, gestational age, timing of prenatal care initiation, or number of prenatal care visits • N= Approximately 3 million

7. Prenatal Care Indices • Trimester of first prenatal visit • 1st trimester, 2nd trimester, 3rd trimester, no prenatal care • Kessner • Adequate, intermediate, inadequate • Adequacy of Prenatal Care Utilization (APNCU) • Intensive, adequate, intermediate, inadequate

8. Outcome Measure: SGA SGA non-SGA Other Variables: Race/Ethnicity Maternal Age Parity Maternal Education Marital Status Other Variables

15. TRIMESTER st Of 1 Vi sit Non - Hispanic white Non - Hispanic black Hispanic st 1 Trimester reference reference reference nd 2 Trimester 1.44 1.42 - 1.47 1.17 1.15 - 1.19 1.16 1.14 - 1.18 rd 3 Trimester / 1. 79 1. 74 - 1. 84 1. 37 1. 34 - 1. 41 1. 4 3 1. 3 9 - 1. 47 No pnc KESSNER Adequate reference reference reference Intermediate 1.39 1.37 - 1.41 1.19 1.17 - 1.21 1.18 1.16 - 1.20 Inadequate 1.85 1.80 - 1.89 1.44 1.41 - 1.47 1.48 1.44 - 1.52 ADEQUACY OF PRENATAL CARE Adequate reference reference reference Intensive 1.07 1.06 - 1.08 0.95 0.94 - 0.97 0.97 0.95 - 0.99 Intermediate 1.25 1.23 - 1.27 1.17 1.14 - 1.19 1.18 1.16 - 1.21 Inadequate 1.68 1.65 - 1.71 1.29 1.27 - 1.32 1.34 1.31 - 1.37 Relative Risk of SGA and 95% confidence intervals by prenatal care index and maternal race/ethnicity

16. >20 >High school unmarried <20 >High school unmarried <20 >High school unmarried Non-Hispanic black Hispanic Non-Hispanic white

17. Adjusted* odds ratios (OR) and 95% Confidence Intervals (CI) for SGA by adequacy of prenatal care index *Model stratified by race/ethnicity adjusted for education, marital status, age, parity

18. Summary • Non-Hispanic black and Hispanic women were more likely to receive less adequate prenatal care, while Non-Hispanic white women more likely to receive adequate prenatal care or enroll in to care in first trimester • Associations between SGA and receipt of prenatal care were generally similar across the three prenatal care indices • Associations between prenatal care indices and SGA was strongest among Non-Hispanic white women

19. Limitations • Trimester of care does not take into account subsequent prenatal care visits • APNCU and Kessner index are based on data that are not well collected on birth certificates • Lack of information necessary to understand the varying composition of the APNCU, intensive group

20. Conclusion • Prenatal care measured by the different indices has similar associations with predicting SGA • Special attention should be taken when making predictions for women who fall into the intensive prenatal care category