Combined adverse effects of maternal smoking and high body mass index on heart development in offspring: evidence for interaction?

OBJECTIVE

To study the influence of a possible interaction between maternal smoking and high body mass index (BMI) on the occurrence of specific congenital heart anomalies (CHA) in offspring.

DESIGN

Case-control study.

SETTING

Data from a population-based birth defects registry in the Netherlands.

PATIENTS: Cases were 797 children and fetuses born between 1997 and 2008 with isolated non-syndromic CHA. They were classified into five cardiac subgroups: septal defects (n=349), right ventricular outflow tract obstructive anomalies (n=126), left ventricular outflow tract obstructive anomalies (n=139), conotruncal defects (n=115) and other CHA (n=68). Controls were 322 children and fetuses with chromosomal anomalies without cardiac anomalies.

MAIN OUTCOME MEASURES: Investigation of whether an interaction between maternal smoking and high BMI influences the occurrence of CHA in offspring by calculation of the synergy factors and 95% CIs.

RESULTS

As opposed to smoking or high BMI alone, the risk for CHA in the offspring of women with high BMI (≥25 kg/m(2)) who also smoked was significantly increased. The adjusted OR was 2.65 (95% CI 1.20 to 5.87) for all CHA, 2.60 (95% CI 1.05 to 6.47) for septal defects and 3.58 (95% CI 1.46 to 8.79) for outflow tract anomalies. The interaction between maternal high BMI and smoking contributed significantly to the occurrence of all offspring-CHA combined, and to the occurrence of all cardiac subgroup anomalies except right ventricular outflow tract obstructive anomalies.

CONCLUSIONS

Maternal overweight and smoking may have a synergistic adverse effect on the development of the fetal heart. Overweight women who wish to become pregnant should be strongly encouraged to stop smoking and to lose weight.