An infant's birth weight is affected by many factors, including the mother's pre pregnancy weight-for-height value and weight gain during pregnancy. A woman’s weight prior to conception influences fetal growth. Optimal weight gain is about 11 to 13 kg. About 900 to 1800g is an average gain during the first trimester. Thereafter 450 g /week during the remaining period of pregnancy. Sharp or sudden increase in weight after the 20th week of pregnancy, may indicate excessive, abnormal water retention which should be carefully watched. There should not be any weight reduction during pregnancy.
A woman who is under weight needs to gain weight prior to conception by taking 700-1000 kcal above normal intake and also exercise to build strong muscles. Overweight also creates problems related to pregnancy and child birth. Such women have more medical complications such as hypertension and gestational diabetes. Infants born to such overweight mothers are likely to weigh more than 4 kgs. More than overweight, such infants are often poorly developed. Since weight loss during pregnancy is not advisable, it is important to lose weight prior to conception and to avoid excessive weight gain during pregnancy.