A baby's cry is all it has to communicate with her mother. Babies sekletal system can be out of place from the pregnancy or birth. Osteopaths and Chiropractors are an excellent resource for checking and realigning your baby if the baby is particularly unsetteld, crying or has reflux or colic. Babies like and need to be picked up, cuddled and attended to immediately.
For information on settling your baby and controleld crying (also known as comfort crying, sleep training or self settling) see Why controlled crying/comforting is harmful and its alternatives in Sleep
For crying out loud - pick up your baby by Queensland University of Technology
"It is also important for parents to have the confidence to trust their instincts when it comes to caring for their baby". However "a joint study with Queensland University of Technology and the Riverton Early Parenting Centre has found many parents of infants up to 12 weeks, were uncertain about how best to settle their crying baby and whether or not it was 'right' to pick them up"(Source).