A great headline but how can one tease apart the mechanics of this study. Nutrition and physical activity was increased. The headline leads you to believe just like popular belief that exercise is the answer to metabolic problems. Yet we know that nutrition is 90% of any changes.

Physiologically, just like in diabetics, exercise (muscular activity) utilizes and lowers blood sugar. This effect would lower the fetus’ exposure to glucose and hence lower insulin in the fetus resulting in less fat generation. This would be a mild effect at best and nutritional changes would be dramatic. Remember that aerobic exercise at any time is going dramatically increase cortisol, a stress hormone that causes metabolic dysfunction and fat deposition. We don’t know the effect of cortisol on the fetus but I’m betting that it can’t be good.

A recent article points to fetal exposure to maternal cortisol: Fetuses experience stress earlier than thought. Remember it is entirely possible that without the exercise, the effect could have been better. It is very difficult to tease out effects when two variables are changed in the same study without multiple study groups.

The “medical headlines” are often misleading. Walking in pregnancy is likely to be very beneficial given what we know in adult females. Beyond that, my best guess is it will be negative. Just food for thought.

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Michael D. Fox, MD
Jacksonville Center Reproductive Medicine
Advanced Reproductive Specialists