Baby's head growth is 2 weeks behind the rest of the body (week 32 of pregnancy). what's the number of weeks threshold for a risk of microcephaly? is it 6 to 10 weeks behind or should we consider two weeks behind as a an indication to microcephaly ?

Microcephaly: What percentile? Has growth relatively slowed? Can large body -90% of average and relatively small head -20% of average, but still be normal( my child-engineer) . Microcephaly is usually defined at birth, though with ultrasound you may see in 3rd trimester(imperfect) . It is head circumference 2 standard deviations below the mean, i.e <3% of newborn have a head that small. f/u/ w neonatologist