BACKGROUND: Low birth weight and preterm birth are independent predictors of neonatal mortality. The terms small for gestational age (SGA) and large for gestational age (LGA) define newborn infants with a birth weight in <10th and >90th percentile for gestational age, respectively. SGA and LGA increases risk of neonatal mortality and may also have long-term effects in development. Socioeconomic risk factors may be associated with SGA and LGA. Exposures associated with higher risk for SGA and LGA should be evaluated in socioeconomically diverse communities.
METHODS: Miami-Dade County birth records for 2015 were used for this analysis. Birth records provide data on socioeconomic factors (such as maternal race/ethnicity, maternal age, maternal education, insurance status, WIC enrollment) and potential risk factors for SGA and LGA (pre-pregnancy BMI, weight gain during pregnancy, pregnancy complications, and parity). The distribution of maternal characteristics and their association with SGA and LGA were evaluated. Adjusted odds ratios (aOR) were obtained from multivariable logistic regression adjusting for socioeconomic factors. All potential risk factors were evaluated as separate exposures.
RESULTS: Our analysis comprised 32,870 women with a live birth in Miami-Dade County in 2015. Of these, 9.9% (n=3,265) met criteria for SGA and 6.7% (n=2,210) met criteria for LGA. The mothers were 60.7% Hispanic, 22.9% Black, non-Hispanic, and 13.4% White, non-Hispanic; 51.6% of the mothers had obtained a high school diploma or less and 55.4% of mothers were unmarried. Maternal characteristics significantly associated with SGA included young maternal age, lower education level, and unmarried status. Maternal characteristics significantly associated with LGA included advanced maternal age, high BMI, excessive weight gain in pregnancy, and having previously had a child. Black mothers were significantly more likely to have an SGA infant and less likely to have an LGA infant. After adjustment, underweight BMI (aOR=1.18 [95% CI 1.04, 1.33]), insufficient weight gain (aOR=1.54 [95% CI 1.39, 1.69]), and maternal hypertensive disorder (aOR=1.78 [95% CI 1.54, 2.06]) were associated with SGA. Overweight BMI (aOR=1.73 [95%CI 1.55, 1.93]), obese BMI (aOR=2.12 [95%CI 1.88, 2.38]), excessive weight gain (aOR=2.19 [1.96, 2.44]), maternal diabetes (aOR=2.51 [95% CI 2.11, 2.99]), and WIC enrollment (aOR=1.23 [95% CI 1.11, 1.39]) were associated with LGA.
CONCLUSIONS: Barriers to education in obtaining normal BMI before pregnancy and adequate weight gain during pregnancy should be addressed to reduce infants that are SGA and LGA. Tools for effective counseling should be provided to WIC programs and clinical providers.