The arrival of a sibling.
D001722:Birth Order; D001942:Breast Feeding; D002653:Child Behavior Disorders / Q000523:psychology*; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009034:Mother-Child Relations; D011247:Pregnancy; D012801:Sibling Relations