New research suggests that women who stop smoking before their 15th week of pregnancy reduce their risk of giving birth prematurely and delivering small babies -- providing a window for doctors to counsel women in early pregnancy to quit before any damage is done to their unborn children.

HealthDay News reported March 26 that researchers led by Lesley McCowan from the University of Auckland analyzed data on 2,504 pregnant women, 80 percent of whom were nonsmokers; 10 percent who had quit smoking; and 10 percent who were current smokers).

The study concluded that women who stopped smoking early on in their pregnancy lowered their risk of delivering undersized or premature babies. Women who did not quit smoking by 15 weeks were at three times greater risk of giving birth prematurely, and twice as likely to deliver smaller babies.

The findings were published online March 26, 2009 in the British Medical Journal.