Around 30 weeks, the growth of the brain markedly increases. Most systems are well developed, and the fetus can see and hear. A baby may survive if born this early, although the lungs may still be immature.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.