Intrauterine Growth Restriction (IUGR)
Q & A: Fetal Growth Restriction
I am 32wks pregnant and had a sono yesterday. We discovered the baby is breech. The femur measured 32 wks but the head measured 35 wks! Is this cause for concern?
No. The head measurement becomes the most unreliable one the later into the pregnancy you get. The femur length pretty much stays accurate, though. The head can easily be off by as much as three weeks in late pregnancy.
Intrauterine Growth Restriction (IUGR) is a condition in which nutritional or vascular compromise affects the rate of growth of the baby. It is a concern, because babies that are "Small for Gestational Age" (SGA) have a higher incidence of fetal distress, still birth, and childhood problems. But the human body, in its wisdom, usually keeps most emphasis on the head, letting the rest of the baby fall behind. We call this "Head-sparing IUGR." So if the head is normal size (or bigger, with error) than the dates, things are usually O.K. If the femur length is far behind the gestational age, there may be head-sparing IUGR. The worse scenario is "Symmetrical IUGR," in which all of the baby is symmetrically SGA. In this case, even the head isn't spared the deficit, and is much more serious. What you described is not worrisome, because it's the opposite of head-sparing.