Pre-pregnancy overweight and obesity, combined with excessive gestational weight gain, increase the risk of adverse pregnancy outcomes in women with polyendocrine metabolic ovarian syndrome.

When a woman has excess body fat before pregnancy, her body becomes more resistant to insulin, which causes her pancreas to pump out more insulin. High insulin levels trigger the ovaries to make too many male hormones, which disrupts normal egg development. During pregnancy, the placenta releases hormones that naturally make the body more insulin resistant, but the pre-existing insulin resistance cannot keep up. This leads to high blood sugar, inflammation, and damaged blood vessels in the placenta. The placenta cannot deliver enough nutrients or oxygen to the baby, which causes preterm birth, low birth weight, or preeclampsia.