Many babies fail to gain weight as expected during the first few days of life. Newborns are expected to loose up-to 10% of their birthweight by Day 5-7 after birth. If they are exclusively breastfed, the breast milk starts to come from Day 2-3 onwards. They then start to gain weight from Day 5-7 and usually regain their birth weight by Day 10.
Most common cause of excessive weight loss is inadequate milk supply in mother, for various reasons. The mother should drink plenty of fluids, eat a healthy diet, try to get adequate rest and put the baby to breast at regular intervals. The technique is also very important and midwives are a great help with that. All these factors help increase breast milk production.
A small percentage of babies may need some top up formula milk or Expressed breast milk if the milk supply does not improve despite the above measures. A health professional should be involved and monitor the weight carefully at regular intervals and ensure that the baby is otherwise well and there is no other factor influencing the feeding and weight.