Contrary to current recommendations, a new study suggests that very obese women should lose weight during pregnancy.
Researchers examined data on consecutive singleton term live births delivered at the maternity unit of the University South Reunion Island over a 16.5-year period from 2001 to 2017. They recorded pre-pregnancy body mass index (BMI), weight gain, and weight of the baby, for 52,092 women who gave birth at full term.
They found that only women with a normal BMI had a balanced risk of having a small or large for gestational age infant (both 10% risk); a crossing point they called the maternal foetal corpulence symbiosis (MFCS). They then examined how this MFCS shifted with BMI and weight gained during pregnancy and pinpointed the optimal weight gain/loss for each BMI category.
The researchers said that while widely used 2009 recommendations from the Institute of Medicine are adequate for normal and over-weighted women, a woman with a BMI of 17 should gain about 22kg instead of the recommended 12.5-18kg. An obese woman with a BMI of 32 should gain 3.6kg instead of the recommended 5-9kg, while women with a BMI of 40 should lose 6kg.