Not being able to play with both hands together at four months is not necessarily a developmental delay. It may be normal, or it may be caused by not creating the appropriate environment, developmental delays, etc. 1. Normal: babies usually play with both hands at around three months, but due to the different developmental conditions of each baby, some babies may play with both hands a little earlier or a little later, but not accompanied by other abnormalities, most of them are normal. 2. not create the appropriate environment: if the baby’s attention is attracted by other things around, the baby does not have the opportunity to try to play with two hands, may also appear four months will not be able to play with two hands together. 3. developmental delay: if the baby will not play with two hands at four months, accompanied by other large motor, physical, language and other aspects of developmental problems, this situation is more suggestive of the existence of the child’s developmental delay. The baby four months will not play with two hands together, there may be other reasons, it is recommended to consult a doctor, under the guidance of the doctor, improve the relevant examination, clear the cause of the disease, symptomatic treatment.