Weight in pregnancy best controlled by diet, study shows
Pregnant women, including those who are obese or overweight, should be encouraged to minimise weight gain through diet, according to major new research from Queen Mary, University of London.
Piling on excess weight during pregnancy increases the risk of complications for pregnant women but doctors have been cautious in advising women on ways to manage weight for fear of any adverse effect on mother or baby.
However, the new study published in the BMJ shows that following a healthy diet, overseen by health professionals, stems excess weight gain in pregnancy and reduces the risk of pregnancy complications such as pre-eclampsia, diabetes, high blood pressure and early delivery.
Half the UK population are either overweight or obese and the rates are rising. Around a third of women gain more than the recommended amount during pregnancy.
Previous research has linked obesity during pregnancy with an increase in a variety of risks including high blood pressure, diabetes, miscarriage, birth defects, blood clots, pre-eclampsia, and even maternal and infant deaths.
The new research, which brings together the results of 44 separate studies, is the largest of its kind and includes data on more than 7,000 women. It was commissioned and funded by the NIHR’s Health Technology Assessment programme.
The researchers investigated the effect of diet, exercise, or a combination of the two. They looked at how much weight women gained throughout pregnancy and whether mother or child suffered from any complications.
Pregnancy and Weight Gain
Gaining the right amount of weight during pregnancy by eating a healthy, balanced diet is a good sign that your baby is getting all the nutrients he or she needs and is growing at a healthy rate.
It is not necessary to “eat for two” during pregnancy. It’s true that you need extra calories from nutrient-rich foods to help your baby grow, but you generally need to consume only 100 to 300 more calories than you did before you became pregnant to meet the needs of your growing baby.
Ask your health care provider how much weight you should gain during pregnancy. A woman of average weight before pregnancy should gain 25 to 35 pounds during pregnancy. Underweight women should gain 28-40 pounds during pregnancy. Overweight women may need to gain only 15-25 pounds during pregnancy. You may need to gain more or less weight, depending on what your health care provider recommends.
In general, you should gain about 2 to 4 pounds during your first three months of pregnancy and 1 pound a week for the remainder of your pregnancy. If you are expecting twins you should gain 35 to 45 pounds during your pregnancy. This would be an average of 1 ½ pounds per week after the usual weight gain in the first three months.
Although all three methods reduced the mother’s weight gain, diet had the greatest effect with an average reduction of nearly four kilograms. Exercise only resulted in an average reduction in weight gain of just 0.7kg. A combination of diet and exercise only produced and average reduction of one kilogram.
How much weight should I gain during my pregnancy?
It depends on how much you weighed before you conceived and how appropriate that weight is for your height. The relationship between your height and weight is expressed in a number called a “body mass index,” or BMI. You can calculate your BMI here.
The guidelines for pregnancy weight gain are issued by the Institute of Medicine (IOM), most recently in May 2009. Here are the most current recommendations:
- If your pre-pregnancy weight was in the healthy range for your height (a BMI of 18.5 to 24.9), you should gain between 25 and 35 pounds, gaining 1 to 5 pounds in the first trimester and about 1 pound per week for the rest of your pregnancy for the optimal growth of your baby.
- If you were underweight for your height at conception (a BMI below 18.5), you should gain 28 to 40 pounds.
- If you were overweight for your height (a BMI of 25 to 29.9), you should gain 15 to 25 pounds. If you were obese (a BMI of 30 or higher), you should gain between 11 and 20 pounds.
- If you’re having twins, you should gain 37 to 54 pounds if you started at a healthy weight, 31 to 50 pounds if you were overweight, and 25 to 42 pounds if you were obese.
- Use our pregnancy weight gain estimator to find out how much you should gain (based on your height and pre-pregnancy weight) and to see how the pounds are distributed.
Women who followed a calorie controlled diet were 33 per cent less likely to develop pre-eclampsia, one of the most dangerous pregnancy complications that presents with raised blood pressure and protein in the urine. Their risk of gestational diabetes was 60 per cent lower, their risk of gestational high blood pressure was 70 per cent lower and their risk of early delivery was 32 per cent lower. However, the researchers acknowledge that these findings need to be confirmed by further large studies.
Crucially, babies’ birth weights were not affected by dieting.
The research was led by Dr Shakila Thangaratinam, a Clinical Senior Lecturer and Consultant Obstetrician at Queen Mary, University of London with researchers in UK and Europe. She said: “We are seeing more and more women who gain excess weight when they are pregnant and we know these women and their babies are at increased risk of complications.”
“Weight control is difficult but this study shows that by carefully advising women on weight management methods, especially diet, we can reduce weight gain during pregnancy. It also shows that following a controlled diet has the potential to reduce the risk of a number of pregnancy complications.
“Women may be concerned that dieting during pregnancy could have a negative impact on their babies. This research is reassuring because it showed that dieting is safe and that the baby’s weight isn’t affected.”