Trend associations of smoking with maternal, fetal, and neonatal morbidity.

Smoking habits, prenatal health, and pregnancy outcome were surveyed among 1700 nulliparous women. During pregnancy, increases in levels of hemoglobin and hematocrit and the frequency of women reporting bleeding and decreases in diastolic pressure and frequency of toxemia were observed with increased maternal smoking. A higher frequency of fetal bradycardia was detected among women smoking greater than or equal to one-half pack per day. With increased smoking there was an increased frequency of abnormal placentas. Mean birth weight and crown-heel length decreased with increased smoking, and neonates born to women smoking greater than or equal to one-half pack per day had a higher frequency of jaundice. The association between smoking and reduced birth weight and crown-heel length persisted after controlling for gestational age, maternal weight gain, prenatal visits, and other confounding variables.