Table 3.

Recommendations for Future Research on Prenatal Physical Activity and Birth Defects

1.	Differentiate between birth defect phenotypes.
2.	Treat different physical activity domains (occupational, leisure time, household, and transportation) as separate exposures.
3.	Ascertain physical activity exposure using biologic measures or questionnaires validated against better measurements (e.g., physical activity records or accelerometers).
4.	Choose potential confounders based on the results of previous studies that are specific to each birth defect examined.
5.	Assess the potential influence of pre-pregnancy body mass index and diabetes on the associations between physical activity and birth defects.