apart from the olfactory bulb , in which there appears to be no initial delay , the estimated initial delays range from 21.7 days ( after fertilization ) for the cerebellum to 29.9 days for the cerebrum , which suggests that the weight of most regions of the brain , as well as body weight , start increasing rapidly only toward the end of pregnancy ( 30 days on the average ) .
C0015914
fertilization
C0032961
pregnancy