The difference was equivalent to the average variation in cognitive scores between children born at a normal gestational weight and those weighing less than 3.5 pounds, the researchers said.

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The overweight women in the study who lost weight post-birth substantially lowered their risk of gestational diabetes compared with those who maintained their weight.

CNN: STORY HIGHLIGHTS

Diabetes diagnosed during pregnancy, known as gestational diabetes, is influenced by hormonal changes and normal weight gain and usually goes away after the baby is born.

CNN: STORY HIGHLIGHTS

While adequate weight gain during pregnancy is important for proper development of your baby, we now know that gaining too much weight is not good, as it can cause problems such as gestational diabetes, preeclampsia, increased risk of Caesarean section and infection, and more difficulty during labor.

CNN: How can I safely control my pregnancy weight gain?