Your OB doctor will refer you to see Perinatal specialist. The ultrasound imaging watch more than size and weight of the fetus. The specialist can see the development of the lung, heart and if there is any major birth defects. Situation is a lot more complicated if the Mom has any underlying medical condition prior to getting pregnant (heart or kidney disease, prior C-section, cancer or HIV+, hepatitis...), the OB doctor will transfer the case to Perinatal doctor. Pregnancy is a lot more complicated than most people think. My daughter used to say 90% of the women don't need any medical help, they can just go into the bush, squat down and get down with business.
