Exercise immediately prior to and during pregnancy restores key tissues in the body, making them better able to manage blood sugar levels and lowering the risk of long term health problems, suggests new research carried out in mice by researchers at the University of Cambridge.
Why it is important
According to the National Health and Nutrition Examination Survey, 33.4% of women 20 to 34 years of age are obese (body mass index [BMI] exceeding 30), and 58.4% are overweight (BMI exceeding 25).
Being overweight or obese during pregnancy increases the risk of complications in the mother, including gestational diabetes, and higher risks of developing metabolic diseases such as type 2 diabetes in the years after pregnancy, both for the mother and the infant.

People have known that exercise can help manage blood sugar levels, reduce the risk of type 2 diabetes and metabolic syndrome in non-pregnant women. Exercise prior to and during pregnancy are also beneficial for mothers and their children in reducing the risk of gestational diabetes.
To know how exercise can influence the tissues of obese pregnant mother, researchers did an experiment in mice.
Why mice?
Mice are a useful model for studying human disease due to the characteristics they have in common with humans biologically and physiologically. The metabolic changes with obesity/obesity-causing diets in the female body during pregnancy are also similar in humans and mice.

Researchers fed mice a sugary, high fat diet to create obesity in the mice. The obese mice were then exercised on a treadmill for 20 minutes a day for at least a week before their pregnancy, and for 12.5 minutes a day until day 17 of the pregnancy, which was about 85% of the whole pregnancy period in mice).
The result
"A moderate level of exercise immediately before and then during pregnancy leads to important changes in different tissues of the obese mother, effectively making the tissues more like those seen in non-obese mothers," says Dr. Amanda Sferruzzi-Perri, who co-led the study.

The key organs of the mother that were affected by exercise were:
1. White adipose tissue – the fatty tissue that stores lipids and can be found in different parts around the body, including beneath the skin and around internal organs;
2. Skeletal muscle – muscle tissue that uses glucose and fats for contraction and movement;
3. The liver – the organ that stores, as well as syntheses lipids and glucose.
White adipose tissue showed the greatest number of changes in response to exercise in the obese pregnant mouse, being restored to a state similar to that seen in the tissue of non-obese mothers.

"Our findings reinforce the importance of having an active lifestyle and eating a healthy balanced diet when planning pregnancy and throughout for both the mother and her developing child," says co-lead Professor Susan Ozanne.
What exercise the mothers should do
The American College of Obstetricians and Gynecologists (ACOG) suggests that expecting moms get at least 30 minutes or more of moderate exercise per day, most (if not all) days of the week.
Not only gym workout is counted in the 30-minute exercise. Three 10-minute walks, 30-minute bike riding, 15-minute vacuuming and 15-minute light yard work can just do the same. Exercise moms can do includes:

General moderate sports:
Swimming
Walking
Jogging
Ellipticals and stair climbers
Group dance or aerobics classes
Indoor cycling
Some intense exercises you can try, if you are already a gym rat:
Kickboxing
High-intensity interval training workouts (HIIT)

Some outdoor sports (better keep these activities up early in pregnancy):
Hiking
Biking
Ice skating, horse back riding and in-line skating
Cross-country skiing and snowshoeing
Best strength and flexibility exercises during the pregnancy:
Weight lifting
Pilates
Barre (a mix of Pilates, yoga and ballet-inspired moves
Yoga
Tai Chi