There are many reasons why one and a half year old babies cry in the middle of the night, and the common reasons are intestinal dysfunction, lack of calcium or baby insecurity. 1. Intestinal dysfunction: when the baby’s intestinal dysfunction, intestinal peristalsis will be abnormal, easy to colic, often manifested in the middle of the night crying. 2. Calcium deficiency: due to the lack of calcium and vitamin D, the baby’s nerve sensitivity will increase, easy to be affected by the environment at night and cry, and in severe cases can also develop into rickets. 3. Insecurity: If the baby is insecure and not appeased accordingly, the nerves will also be in a sensitive state, and the baby will cry in the middle of the night. If the baby often cries at night, you need to go to the hospital in a timely manner for relevant examinations, to clarify the cause of crying and take appropriate measures for treatment.