Birth Weight of Offspring, Maternal Pre-pregnancy Characteristics, and Mortality of Mothers: The Jerusalem Perinatal Study Cohort
Received 17 June 2008; accepted 17 November 2008.
Purpose
To explore the association between birth weight in offspring, a marker of the intrauterine environment, and mortality in their mothers, taking into account maternal pre-pregnancy characteristics, including maternal body mass index (BMI), smoking, and socioeconomic status. Distinguishing the effects of offspring's birth weight and pre-pregnancy characteristics on maternal outcome may provide clues regarding mechanisms underlying the association between birth weight and maternal mortality.
Methods
We studied long-term total mortality (average follow-up period, 29.1 years) in a population-based cohort of 13,185 mothers, aged 15 to 48 years at their offspring's birth, who delivered in West Jerusalem during 1974 through 1976.
Results
Univariate and multivariate Cox-proportional hazard models used to estimate the hazard of overall mortality among mothers indicated a nonlinear relationship with birth weight of offspring when introduced into the models as a continuous variable, and a linear positive association with maternal pre-pregnancy BMI. Inclusion of maternal BMI and other pre-pregnancy characteristics in the model did not alter the association between offspring's birth weight and mothers’ all-cause mortality. When birth weight was introduced as a categorical variable, higher mortality was observed among mothers who gave birth to babies with birth weight less than 2500 g (hazard ratio [HR] = 1.90; 95% confidence interval [95%CI], 1.23–2.94) as compared to mothers whose offspring had birth weight between 3000 and 3499 g. The HR for mothers who gave birth to babies with birth weight 4000 g or more was 1.30 (95%CI, 0.88–1.91).
Conclusions
Independent of pre-pregnancy maternal BMI and other characteristics, birth weight of offspring was associated with mortality in their mothers, suggesting that intrauterine metabolic events reflected by birth weight and not explained by maternal obesity, smoking, and socioeconomic status have remote consequences for maternal health. These findings underline the need to explore specific genetic and/or environmental mechanisms that account for these associations.
aUnit of Epidemiology, Hebrew University School of Public Health, Jerusalem, Israel
bThe Department of Hematology, Hadassah-Hebrew University, Jerusalem, Israel
cThe Department of Human Genetics, Hadassah-University Hospital, Jerusalem, Israel
dThe Department of Psychiatry, New York University School of Medicine, New York City
eThe Cardiovascular Health Research Unit, Departments of Medicine and Epidemiology, University of Washington, Seattle, WA
Address correspondence to: Yechiel Friedlander, PhD, Unit of Epidemiology, Hebrew University-Hadassah Braun School of Public Health, POB 12272, Jerusalem 91120, Israel. Tel.: +972-2-6777805; fax: +972-2-6449145.
ABSTRACT