Weight Loss During Pregnancy: Ketones and Safe Practices

Question
Some internet sites say that if you lose too much weight during a pregnancy, particularly if you are exercising, you develop ketones which can damage a developing baby?  Other sites say this is not true.  When my wife changes to a healthier eating plan she tends to lose 2-3 kilos per week for a short period (say 3-4 weeks) before  weight loss slows down.  She wants to do this now, when pregnant.  Is this ok, so long as still having three decent meals a day and two snacks?

Answer
Weight loss during pregnancy should only be attempted by obese women.

To optimize both maternal and fetal health, your wife should eat as healthily as possible and take a pregnancy vitamin daily, as well as  get a moderate amount of exercise on most days of the week.

If your wife is currently overweight, then she should consult with a registered nutritionist who can determine her ideal daily caloric consumption and advise her on how to improve her overall nutritional intake. This will help prevent excessive fat gain and reduce the risk of gestational diabetes. Overweight and obese women do not need to increase fat storage during pregnancy.

Ketone in the urine is a sign of very low carbohydrate intake. These types of severe carbohydrate restriction diets should not be attempted during pregnancy.