June 06.

Health effects of smoking tobacco, smokeless tobacco, and nicotine:

Risks in pregnancy

Summary:

· Cigarette smoking: There is strong epidemiological and biochemical evidence that cigarette smoking during pregnancy significantly increases the risk of low infant birth weight, premature labour and perinatal mortality, also sudden infant death syndrome.¹

· Smokeless tobacco:

Sweden: birthweight is lowered by smoking, and to a lesser extent by smokeless.¹

India Use of Indian smokeless tobacco in Indian women is associated with increased risk of stillbirth and decreased birth weight.^{2 4}

Africa Use of African snuff in Black African women does not decrease birthweight significantly.³

• Nicotine: All organs except the brain complete their development in the first 3 months of pregnancy, but the brain continues to grow, and while growing is susceptible to nicotine.⁴

Conclusion:

• There is no safe dose of nicotine in pregnancy. Nicotine replacement therapy is justified if smoking cessation is otherwise unlikely. Patches that are used for 16 rather than 24 hours are preferred.
• Smoking greatly, and smokeless to a lesser extent, puts the fetus and infant at risk.
• Smoking in pregnancy reduces birthweight, increases risk of preterm delivery, and perinatal mortality. Smokeless tobacco has similar but generally less severe effects. In Mumbai women, presumably often with marginal nutrition, income, or health services, all cause mortality was increased. The content of smokeless tobacco does not plausibly account for these results, as the smokeless effects in pregnancy may be due to its nicotine.
• During pregnancy smoking and smokeless tobacco should be avoided, and nicotine only considered as a temporary stop smoking aid.

Birth weight

Compared with no use of tobacco or nicotine	Cigarette smoking	Smokeless tobacco as used	Nicotine only	Second hand smoke (not from mother)
Western countries	Accounts for 2.7% to 5.2% of the variance in birthweight.^1	Few women use smokeless. No data
India (Mumbai)^2	Few women smoke.	Reduced by 105g. on average.	No data	No data
South Africa^3	Reduced by 165 g	Reduced by 17g Not significant.	No data	Birthweight not affected.

Pre-term delivery

Compared with no use of tobacco or nicotine	Cigarette smoking	Smokeless tobacco as used	Nicotine only	Second hand smoke (not from mother)
Western countries	Preterm delivery risk increased; OR 1.98.^1	Preterm delivery risk increased OR 1.57^1	No data
India (Mumbai)	Few women smoke	Risk of pre-term birth before 37 weeks was increased 40%, and five fold before 32 weeks.^3
South Africa	No data	Shorter gestational age.^5	No data

Mortality risks

Compared with no use of tobacco or nicotine	Cigarette smoking	Smokeless tobacco as used	Nicotine only	Second hand smoke (not from mother)
Western countries	Main risk factor for sudden infant death syndrome in NZ.	No data	No data.
India (Mumbai)	Risk increased.	Stillbirth risk increased 2.6 times^6	No data
South Africa	No data	No data	No data

1 England LJ, Levine RJ, Mills JL, Klebanoff MA, Yu KF, Cnattingius S. Adverse pregnancy outcomes in snuff users. Am J Obstet Gynecol 2003;189:939-43. (Sweden)

2 Secker-Walker RH, Vacek PM. Relationships between cigarette smoking during pregnancy, gestational age, maternal weight gain, and infant birthweight. Addict Behav 2003; 28: 55-66. (USA)

3. Gupta PC Sreevidya S. Smokeless tobacco use, birth weight, and gestational age: population based prospective cohort study of 1217 women in Mumbai, India. BMJ 2004; 328: 1538.  

4 Oncken CA, Hardardottir, H, Smeltzer JS. Human studies of nicotine replacement during pregnancy. Ch. 11 in Ncotine Safety and Toxicity ed. NL Benowitz. Oxford OUP 1998.

5. Steyn K, de Wet T, Salloojee Y, Nel H, Yach D. The influence of maternal cigarette smoking, snuff use and passive smoking on pregnancy outcomes: the Birth to Ten Study. Paediatric and Perinatal Epidemiology 2006; 20: 90-99. (South Africa)

6. Gupta PC, Subramoney S. Smokeless tobacco use and risk of stillbirth: a cohort study in Mumbai, India. Epidemiology 2006 Jan;17(1):47-51.

Dr Murray Laugesen QSO chair; Prof Ross McCormick, Sir John Scott KBE, Trish Fraser MPH, Dr Marewa Glover, Trustees

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