Sociodemographic factors associated with preterm birth and low birth weight: A cross-sectional study

Preterm birth and low birth weight are two public health problems worldwide associated with higher morbidity and perinatal death risk.

To determine the incidence and socio-demographic factors associated with preterm birth and low birth weight in Spanish women.

Cross-sectional study with data from women who gave birth in Spain during 2015 extracted from the Statistical Bulletin of births (National Institute Statistics). Records analysed were 331,449. Single births from 22 weeks gestation and fetuses with weight ≥ 500 g were included. Unadjusted and adjusted odd ratios with 95% confidence interval in a multiple logistic regression model were calculated. Variables associated with both health problems were considered dependent variables.

Preterm birth rate in Spain was 6.7% and low birth weight rate was 7.3%. Socio-demographic variables associated with preterm birth were maternal age ≤19 years, immigrant mothers, educational level ≤ secondary studies, and women living in large cities. Low birth weight was related to maternal age ≤19 years and ≥35 years, educational level ≤ secondary studies, and single mothers. Not having previous children and caesarean births were associated with both risks.

The rates of both risks decreased in Spain, one of the countries in Europe where maternal age at having the first child has increased the most and with the lowest birth rate in the world. Maternal age, educational level, maternal nationality, marital status and population size were associated with one or both risks, so the results of this study could be especially relevant to the clinical practice.