In the US, the Case of Baby Doe, Bloomington, 1982, which ultimately led to the Baby Doe Law, illustrates this. Here parents refused a simple surgical procedure which was common practice on their baby, who was born in with Down's syndrome, a tracheoesophageal fistula and esophageal atresia, because of the emotional advise they received from obstetrician, himself a parent of a child with Down's syndrome.
Doctors are human and, as such, may have personal views which could lead them to surreptitiously lean the parents or patients towards or against a certain type of treatment.