Do babies with small head have immature brain development?

Q: My four months old baby was born at 34 weeks and one day. Her birth weight was 2.394 kg and her head circumference was 31cm and length was 41 cm. Now she weighs 4.9 kg and her head circumference is 37 cm and length is 59 cm. Is it normal? Do babies with small head have immature brain development? She still looks very tiny.

A:She seems to be growing fine in all parameters. I don't think we can infer that she has a small and immature brain. We need to monitor her growth and development over a period of time. By 2 years of age if her head size and development is fine, it is normal even though she may look tiny.