Fetal development in pregnancy week 16:fetus in fourth month Over the past three weeks your astounding growing baby has managed to stretch yet another 2 full inches (totaling about 4.5 inches) and weighs around 3.5 ounces. Yessireee, that’s some pretty serious growth... and with it comes several physical developments! For starters, their head to body ratio is finally starting to even out a bit as the rest of the body is actually growing faster than the head at this point. Yes, your little light bulb is not so top-heavy. Their adorable little limbs have lengthened, almost reaching their normal proportions which they will have at birth. Their eyes are still closed but moving and if you had an ultrasound, which many doctors recommend you have at about this time, you may even see your little one sucking on a thumb, not to mention the necessary signifiers to let you know whether you’ve got a wee lad or lassie.