Preterm birth
Among the 457,200 women aged 15 to 44 who gave birth between January 2014 and September 2015, there were 231,942 white, 141,392 black, 30,903 Hispanic, and 52,963 were of another race or ethnicity. The preterm birth rate within the overall cohort was 8.9%. This was highest for black women (9.9%) compared to both white (7.3%) and Hispanic women (6.2%) (Fig. 1).
Perinatal service utilization
More than four in five women (81.1%) accessed at least one prenatal visit during 30 weeks prior to delivery (Fig. 2). Hispanic women had the lowest prenatal visit rate (50.3%) compared to black (87.2%), white (82.43%), and other racial/ethnic women (76.7%). Less than one thirds (28.3%) of women included in this study had 8 or more prenatal visits 30 weeks prior to birth. Approximately one third (32.2%) had at least one high-risk pregnancy visit during 30 weeks prior to delivery.
Medical co-morbidities at the time of delivery associated with preterm birth
The prevalence of hypertension was the highest for black women (16.1%) (Table 1). Hispanic women had the highest prevalence of diabetes among all groups (11.7%), and white women had a significantly higher prevalence of drug dependence (1.3%) and smoking (0.5%) than both black and Hispanic women.
Table 1 Major medical co-morbidity rates in pregnant women enrolled in Medicaid Multivariate analysis
In the regression analysis, the odds of preterm birth among black women was 35% higher than those for white women, controlling for age, smoking, drug and alcohol dependence, diabetes, hypertension, high-risk pregnancy, and the total number of prenatal visits occurring 30 weeks prior to delivery (OR=1.35; 95% CI [1.32, 1.38]) (Table 2). The odds of preterm birth in Hispanic women were 17% less than white women after adjusting for all other variables (OR=0.83; 95% CI [0.76, 0.87]). The odds of preterm birth were more than double for women diagnosed with drug dependence (OR = 2.21; 95% CI [2.02, 2.42]) or alcohol dependence (OR = 2.09; 95% CI [1.71, 2.55]) after adjusting for other variables. Hypertension (OR=1.82, 95% CI [1.77, 1.87]), maternal smoking (OR=1.50) and diabetes (OR=1.27) were also associated with higher odds of preterm birth.
Table 2 Logistic Regression Model Estimating Preterm Rates among Women Enrolled in Medicaid When stratified, drug dependence was associated with higher odds of preterm birth in both black and white women after adjusting for age, prenatal visit count and other medical conditions. The level of the association was higher in black women (OR = 2.56, 95% CI [1.92, 3.41]) compared to that of white women (OR = 2.12, 95% CI [1.91, 2.34]) (Table 2). Neither drug nor alcohol dependence was significantly associated with higher odds of preterm birth in Hispanic women (p> 0.05). Maternal smoking was associated with higher odds of preterm birth only for white women (OR=1.64, 95% CI [1.38, 1.94]). In Hispanic women, diabetes (OR=1.44, 95% CI [1.27, 1.64]) and hypertension (OR=1.98, 95% CI [1.74, 2.26]) were associated with higher odds of preterm birth (Table 2). Maternal smoking was associated with higher odds of preterm birth only for white women (OR=1.64, 95% CI [1.38, 1.94]).
The predicted probabilities of preterm birth among women of different races and ethnicities were estimated by medical co-morbidities and by total prenatal visit counts prior to delivery (Fig. 3). White women diagnosed with drug dependence had a 14.0% predicted probability of preterm birth, whereas black women with drug dependence had a predicted probability of preterm birth of 21.5%.
For all racial and ethnic women, those with eight or more prenatal visits were associated with a decreased predicted probability of preterm birth. Compared with women who did not have any prenatal visit, the predicted probability of preterm birth among women with 8 or more prenatal visits decreased from 12.2 to 6.4% in black women, 8.3 to 5.3% in white women, and from 6.7 to 4.4% in Hispanic women, adjusted for age and other medical co-morbidities.