Morris - fetal growth terms
So, there’s a number of definitions we use to describe babies that are too big or too small. We use, for example, ‘small for gestational age’. For each gestational age we have a normal weight and length of the baby that we should see. We can measure the baby’s bones; so femur length. We can measure the head circumference. We can measure the abdominal circumference and we can calculate whether or not that baby based on those measurements is small for gestational age or appropriate for gestational age or large for gestational age. The small for gestational age baby, we also can describe that with a few different terms and sometimes they’re interchangeable. A baby could be small for gestational age but actually just be on the bell curve for that age and be at the 5th centile or the 10th or the 30th centile as opposed to being an average size baby. So you can have a small healthy, small for gestational age baby. I had four of them because I’m not a big person and my husband isn’t either and they’re all healthy. But if you have a baby that should have been able to grow more than it did but it didn’t, that’s what we would call an intrauterine growth restricted baby. So that baby genetically was predetermined to be bigger than it is. And for example, when we get very poor placental function, the baby can’t grow and that baby would have intrauterine growth restriction. So intrauterine growth retardation actually refers to the baby that is smaller than it should be. And small for gestational age may be an intrauterine growth retarded baby or it may be a completely healthy baby that’s supposed to be six pounds when it’s born.
Large for gestational age babies are babies that are too large and most of the time the large for gestational age baby is due to diabetes. It’s the commonest cause for large for gestational age. There is the baby that’s just big because, you know, dad was a Winnipeg Blue Bomber and they’re just big. Those babies are healthy but large for gestational age and then there’s the baby that is big because it was exposed to too much glucose in utero the whole time. So these babies have; we can actually recognize them on fetal assessment ultrasound; they’ll have a different fat distribution. They’ll have a lot of abdominal fat and fat around the neck and chest. They will be usually over the 95th centile and some of these babies are like 12, 13 pounds if you leave them in till term. They’re, actually families think they’re really cute but they’re really fat. You can’t see their neck, they’re just. And it’s sad because you’re seeing an obese baby that’s two minutes old. Anyway, that’s the large for gestational age baby that we’re trying to prevent.
