"Smoking during pregnancy increases the risk of stillbirth," the researchers write in the British Journal of Obstetrics and Gynaecology. "The use of NRT (nicotine replacement therapy) in pregnancy is a possible harm reduction strategy," they add.
Using national data, Dr. K. Strandberg-Larsen, at the University of Southern Denmark in Copenhagen, and colleagues gathered information on NRT use and smoking for 87 032 singleton pregnancies.
Two percent of women reported using nicotine replacement during pregnancy. Of these women, 14 percent had not smoked during pregnancy, 30 percent had quit smoking during pregnancy, and 56 percent continued to smoke.
There were 495 stillbirths, 8 of them among the NRT users.
Compared to women who did not use NRT, those who did had a 43 percent lower risk of stillbirth after accounting for other risk factors. Even for women who continued to smoke while using NRT, the risk was reduced by 17 percent compared to nonsmokers.
By comparison, smokers who did not use NRT during pregnancy had a 46 percent higher risk of having a stillbirth.
Whether gum or patch, the type of NRT did not affect the risk of stillbirth.
There are several possible explanations for the low risk of stillbirth among NRT users, according to the researchers.
It could be that NRT users comprise a group of healthier smokers who are more likely to follow preventive advice during pregnancy. It's also possible that "medical risk factors may have been less prevalent among NRT users than among non-users," the investigators explain.