Weight gain in pregnancy

A newborn's birth weight and a mother's weight after pregnancy is influenced not just by how much weight she gains during pregnancy, but also by the source of her excess weight. It is known that too little or too much weight gain during pregnancy can harm both the mother and her newborn. As a result, researchers at the Baylor College of Medicine, Texas took up the study to investigate which aspects of pregnancy weight gain are more important to infants' and mothers' health than others. Researchers conducted sophisticated body scans of 63 women before, during and after their pregnancies. They recorded changes in women's weight from water, protein, fat, and potassium - a marker for changes in muscle tissue, a component of lean mass. Weight gain during a pregnancy can be from 4 to 15 kg. Women with normal weight gain an average of about 7 to 8 kg during pregnancy, and underweight women gain even more.

Women who gain weight during pregnancy add on both fat and lean mass, including weight from water and protein. But although women need to gain enough weight during pregnancy to produce a healthy-sized infant, researchers have found that only increases in lean mass, and not fat mass, appeared to influence infant size. And the more fat women gained during pregnancy, the more excess fat they had after delivery. Gains in lean mass, in contrast, had no influence on a woman's post-pregnancy weight. These findings suggest that when it comes to weight gain during pregnancy, the amount of lean mass a woman packs on is a "critical component" of the newborn's health. Women should accept that it is "inevitable" they will gain a certain amount of fat during pregnancy. Excessive gains in fat mass come from gaining an excessive amount of weight during pregnancy. Gaining too much weight during pregnancy can increase the risk of gestational diabetes, pre-eclampsia and difficulties during delivery. Gestational diabetes can lead to the birth of a larger-than-normal baby, while pre-eclampsia, characterised by dangerously high blood pressure, can progress to a more serious, seizure-inducing condition. However, gaining too little weight during pregnancy can result in babies being born with a low birth weight, which is associated with health problems for the infant.

Regardless of how much fat women gained during pregnancy, only lean body mass appeared to influence the size of the infant, with women who gained more lean body mass giving birth to larger infants.

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