Smoking during pregnancy associated with aerobic fitness of children

1. Maternal smoking during pregnancy was associated with lower aerobic fitness among male military recruits.

2. Maternal body mass index (BMI) and weight gain during pregnancy were associated with aerobic fitness, but this relationship was mediated by recruits’ own BMI.

Evidence Rating Level: 2 (Good)           

Study Rundown: Tobacco use in pregnancy has been associated with numerous adverse neonatal and childhood outcomes including spontaneous abortion, placental abruption, preterm delivery, low birth weight, sudden infant death syndrome, asthma, and childhood obesity. These associations have been well documented, but much less is known about the impact of smoking during pregnancy on longer-term health outcomes. Prior work has shown that maternal BMI and gestational weight gain are associated with offspring anthropometrics. While being overweight has been demonstrated to be associated with lower aerobic fitness, the direct relationship between maternal BMI and offspring fitness has not been previously evaluated. In the present work, the authors explored the relationship between maternal BMI, gestational weight gain, and smoking with aerobic fitness of their offspring. They found that maternal smoking during pregnancy was associated with lower aerobic fitness; maternal BMI and gestational weight gain were associated with lower fitness but this association was mediated by study participants’ BMI.

Strengths of the study included a prospective population-based dataset with outcomes collected over many years. Limitations included convenience sample with limited generalizability to other groups, as male military recruits are likely to have a different fitness level from the general population. Additional prospective studies in a more diverse population are needed to further characterize the effect of maternal smoking during pregnancy on long-term fitness, as well as fitness-related clinical outcomes, of their children.

Click to read the study in BJOG

Relevant Reading: Maternal smoking during pregnancy and child overweight: systematic review and meta-analysis

In-Depth [prospective cohort]: This study evaluated the relationship between maternal smoking during pregnancy and exercise performance in 508 male Finnish military recruits. The primary outcomes of interest were aerobic fitness, measured with the Cooper test, which measures the distance an individual can run in 12 minutes, and strength performance, assessed with a muscle fitness index, which scored participants on repetitions of various exercises.

Maternal smoking during pregnancy (p = 0.038), physical inactivity at age 15-16 years (p = 0.015), participant BMI (p < 0.001) and participant smoking (p = 0.011) were independently associated with lower offspring performance on the Cooper test. Maternal BMI and gestational weight gain were associated with Cooper test score (p < 0.001 for both), but recruit BMI mediated this association. The weight of offspring was associated with their mothers’ pre-pregnancy BMI category (p < 0.001) and whether their weight gain during pregnancy was appropriate or excessive (p = 0.005).

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