For moms-to-be, a new study finds that moderate-intensity exercise three times a week during your second and third trimesters halves the risk of your newborn being overweight.

Researchers said that regular exercise cuts the risk of a having a baby with macroscomia, known as "big baby syndrome," when a newborn weighs more than four kilos, which can boost the risk of needing a caesarean delivery.

These findings come from research led by Rubén Barakat of the Polytechnic University of Madrid, Alejandro Lucía of the European University of Madrid, and Jonatan Ruiz of the University of Granada. Together with their team, they ran a series of programmed training sessions for a sample of 510 sedentary pregnant women, meaning that they exercised for less than 20 minutes or fewer than three days a week.

The intervention group followed a training program that consisted of 55-minute sessions of aerobic, muscle strength and flexibility exercises three days a week from weeks 10-12 to weeks 38-39 of pregnancy.

The results showed that while the training sessions did not reduce the risks of gestational diabetes mellitus, they did reduce the risks of macrosomia (down by 58 per cent) and caesarean delivery (which fell by 34 per cent).

The results of their study, announced Tuesday, have been published in the British Journal of Sports Medicine.

But before you begin an exercise program, be sure to talk to your doctor about any risks with your pregnancy. The Mayo Clinic in the US advises that for most pregnant women at least 30 minutes of moderate exercise is recommended on most days, and walking is a great exercise for beginners. Other good choices: swimming, low-impact aerobics, and cycling on a stationary bike.

A 2011 study found that women who gain too much weight during pregnancy tend to have newborns with a high amount of body fat, regardless of the mother's weight before pregnancy.

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