Family Income and Low Birth Weight in Term Infants: a Nationwide Study in Israel

Abstract

Objectives: To explore the influence of income on Low Birth Weight (LBW), taking into account other socio-economic measurements.

Methods: This retrospective cohort study is based on the Israel National Insurance Institute (NII) database. The study population included 58,454 women who gave birth between 2008 and 2013 to 85,605 infants. Only singleton births at term (gestational age in weeks = 37 and later) were included. Logistic regression models with a Generalized Estimating Equation approach were used in order to assess the independent effect of income and Socio-Economic Regional Index (SERI), maternal age, family status, population group and occupational status on LBW. In addition, sibling analysis was conducted to assess the influence of a change in income on birth weight (BW) among 21,998 women.

Results: Lower income was associated with higher odds of LBW (odds ratio (OR) = 1.266; 95% CI:1.115-1.437. Immigrants from Ethiopia, Bedouins from the Negev, the youngest, the oldest, and single mothers had higher odds for LBW newborns. Compared to women whose income quartile had not changed between the most recent and the first births, for women who experienced a deterioration of three and two quartiles in family income, significantly lower birth weight was observed at the time point with lower income: 103 g (p = .049) and 71 g (p = .008), respectively. Improvement in income revealed an almost linear increase in birth weight.

Conclusions for practice: In an effort to prevent LBW associated mortality and diseases, interventions should be focused first of all on women from population groups who are disadvantaged.

Keywords: Income; Low Birth Weight; Population group; Socio-Economic Position.