Macrocephaly (Big Head), Head Lag and slight delay in developmental milestone

Doctor says that my 5 months plus baby head circumference has grown too fast and is on the bigger side (more than 97th percentile). There is also head lag and baby is unable to turn over yet (soon I think, already trying very hard). My 5 months plus baby is born 37th week (not considered premature). Doctor is proposing MRI (detailed scan) compared to Ultrasound to check on baby's head. However MRI will require baby to be under GA (General Anaesthesia). Anyone who are in a similar situation or have any other suggestions and if we should go ahead with the doctor's advice for peace of mind? If baby is just slower and able to hit milestones in the next couple of months, should I just ignore the MRI check as I do not wish to let my baby undergo unnecessary procedures. #advicepls #pleasehelp #othersuggestions #babyhead #delayedmilestones