Various effects of smoking in pregnancy are described:

• increased risk of premature delivery
• associated with intrauterine growth retardation - infants born to mothers who smoke are, on average, 170 g lighter; there is x2 risk of having an infant with a birthweight of under 2500g compared with non-smoking mothers
• perinatal deaths are more common in infants born to mothers who smoke
• spontaneous abortions are more common in mothers who smoke (1)

The risk of pre-eclampsia is LOWER for women who smoke than for non-smoking mothers.

NICE state that (2):

• women who smoke or who have recently stopped should be offered smoking cessation interventions. Interventions that appear to be effective in reducing smoking include advice by physician, group sessions, and behavioural therapy (based on self-help manuals)
• women who are unable to quit smoking during pregnancy should be encouraged to reduce smoking

Reference:

1. Roberta B (1999). NEJM, 340, 333.
2. NICE (2003). Antenatal care.