1. Height and weight development The height and weight of a five-month-old baby is one of the issues that parents are most concerned about. Under normal circumstances, the height of a five-month-old baby for boys and girls is 64.4 cm and 62.9 cm respectively, and the weight is 7.3 kg and 6.8 kg respectively. However, it should be noted that each baby’s growth and development is different.