I had my 4th ultrasound today. They did one at 9 weeks to confirm, 13 weeks (she never said why), 21 weeks (anatomy scan) and today at 25 weeks (follow up because wiggle worm wouldn't sit still for spine measurement at anatomy scan). Today she said baby looks great and is measuring a week ahead but that I'll have ANOTHER ultrasound next appointment at 29 weeks to make sure baby's head isn't getting too big for vaginal birth?? I'm a little confused as this will still be hopefully way before birth and she says his growth is perfect. Any ideas as to why she needs another ultrasound?? Pregnancy has been textbook so far.