Intergenerational effects of preterm birth and reduced intrauterine growth: a population-based study of Swedish mother-offspring pairs.

OBJECTIVE: To estimate the intergenerational effects of preterm birth and reduced intrauterine growth.

DESIGN: Population-based cohort study.

SETTINGS: Mother-first-born offspring pairs recorded in the Swedish Medical Birth Registry.

POPULATION: Children born before 2001 to 38 720 women born in 1973-75.

METHODS: The relationships between the mother's and the child's birth characteristics were estimated using logistic regression analysis. Adjustments were made for smoking habits, body mass index (BMI), and current and childhood socio-economic conditions. Analyses were performed on all mother-offspring pairs and on the pairs for which information on neither of the included background variables was missing (n= 24 520).

MAIN OUTCOME MEASURES: Preterm birth (<37 weeks of gestation) and small for gestational age (SGA) (<-2 SD of the Swedish standard).

RESULTS: Mothers who themselves had been born preterm were not significantly more likely to deliver their own children preterm, compared with those who had been born at term (adjusted OR 1.24, 95% CI 0.95-1.62). Also, preterm birth in the mothers did not influence the occurrence of SGA in the children. However, the odds ratio for giving birth to SGA and preterm children, respectively, was higher among SGA mothers (OR 2.68, 95% CI 2.11-3.41 and OR 1.30, 95% CI 1.05-1.61). Mothers whose intrauterine growth was moderately reduced but who did not meet the criterion of being born SGA were also at higher risk of giving birth to both preterm and SGA children, respectively.

CONCLUSIONS: The present study showed evidence of intergenerational effects of reduced intrauterine growth even when socio-economic factors as well as BMI and smoking were adjusted for. There was, however, no consistent intergenerational effect of preterm birth.