The study, which was completed by Norwegian doctors, found that the chance of delivering a larger than gestational age baby reduced by 28% if mom exercised regularly throughout the pregnancy. The mothers in the study did not just exercise during the first trimester, but kept up their regular fitness activities through the second and third trimesters as well.
Doctors believe that adding regular exercise to the other common changes women make during pregnancy, like reducing caffeine intake, is the proverbial "icing on the cake", as stated by Dr. Robert Welch of Southfield Michigan's Providence Hospital.
Babies that are born weighing more than 8.8 pounds have what doctors call fetal macrosomia. Giving birth to babies that weigh more than normal increases the chance of birth related injury to mom and baby. Mothers are also at an increased chance of having a C-Section with higher weight babies. Researchers have also linked the birth weight of a baby with fetal macrosomia to obesity later in life.
The number of babies born with birth weights higher than average seems to be rising in a parallel fashion to fewer mothers choosing to exercise while pregnant.
The women in the study all carried their babies to 37 weeks gestation or longer. About 80% of the mothers were of normal weight while just 20% were overweight. The overweight mothers did not fall into the obese category.
According to researchers, the exercise habits of the mothers before they were pregnant did not have an effect on the outcome which means mothers who choose to begin exercising as a healthy choice for baby could see the same birth weight effects as those who exercised regularly before they were pregnant.
Source: Obstetrics & Gynecology 2009