To help with constipation in babies, it is important to first consider their weight in order to calculate the correct dosage of laxatives. You can typically give a dose of 0.2 to 1 gram per kilogram of body weight per day, without exceeding 17 grams per day. If your baby is struggling to pass stool, you can try gently moving their legs towards their stomach to create some pressure and help them. It is important to monitor the effectiveness of the treatment and adjust the dose if needed. It may take a few days to a few weeks for the new formula to have an effect on the constipation.