Vitamin C Supplements as a Strategy to Improve Infant Lung Function
Smoking before and during pregnancy is a bad idea. Not only does smoking, or heavy smoking in the past, reduce fertility rates and increase risk of miscarriage, there can be effects on the embryo or fetus that continue into infancy, childhood and can be lifelong. For example, cigarette smoke directly reduces the amount of oxygen that travels across the placenta to the fetus and causes intra-uterine growth retardation. Newborns born to women who smoke during pregnancy are smaller on average and are more likely to have a low birth weight. Infants of smokers are more likely to have birth defects. The nicotine from cigarettes crosses the placenta, where it alters lung development of the fetus. This increases risk of respiratory complaints including wheezing, coughing, and risk of lower respiratory tract infections.
Despite smoking being a well-known risk factor for pregnancy and birth complications, many women continue to smoke while pregnant. For example, 11% of pregnant women in Germany reported cigarette smoking, 11% of pregnant women in the USA reported smoking in the third trimester, and 19% of UK women reported smoking while pregnant. It seems that some women are unwilling or unable to stop smoking while pregnant.
Recently, based on some studies based on an animal model of maternal smoking (see Proskocil, and recent studies by Sekhorn), a randomized clinical study was performed by McEvoy and co-workers to see whether maternal supplementation with vitamin C could improve measures of respiratory health in infants born to women who smoked. Pregnant female smokers were recruited into the study before 22 weeks’ gestation, and took 500 mg vitamin C daily until the end of pregnancy, or a control supplement. Although the researchers provided smoking cessation counseling at consent, randomization, and all study visits, only 10% of women quit smoking during the study.
Newborns’ pulmonary function test results were better when their mothers had taken vitamin C supplements during pregnancy. This improvement was clinically relevant. Incidence of wheezing and the use of medication for wheezing was also reduced in the vitamin C group compared to placebo.
These results show that some of the damage cigarette smoking causes to the respiratory system of developing fetuses can be reduced if pregnant smokers take a reasonably high dose of vitamin C. Why is this helpful? Vitamin C recommendations for smokers are higher than for smokers by around 50%, as the cigarette smoke breaks down vitamin C in the body, therefore the additional vitamin C may help pregnant smokers meet minimum recommendations. Nicotine also affects the amount of collagen that forms in the airways during prenatal development, and alters the internal structure of the lung; vitamin C partially blocks these effects. In addition, cigarette smoke increases oxidative stress on cells, which may be counteracted by higher levels of vitamin C.
These results are encouraging, especially given that compliance to the vitamin C treatment was around 80% even though 90% of the women did not stop smoking after receiving counseling. Even so, the authors did not have a large enough sample, or start supplementing early enough, to see whether vitamin C reduced rates of miscarriage, birth defects, low birth weight or other negative effects of smoking. Women who are planning a pregnancy or are pregnant should avoid cigarette smoking as a first line strategy, and vitamin C could be used to mitigate some of the effects on the respiratory system if women are unable to stop smoking.
McEvoy CT, Schilling D, Clay N, Jackson K, Go MD, Spitale P, Bunten C, Leiva M, Gonzales D, Hollister-Smith J, Durand M6, Frei B, Buist AS, Peters D, Morris CD, Spindel ER. Vitamin C Supplementation for Pregnant Smoking Women and Pulmonary Function in Their Newborn Infants: A Randomized Clinical Trial. JAMA. 2014 May 18. doi: 10.1001/jama.2014.5217. [Epub ahead of print]. http://www.ncbi.nlm.nih.gov/pubmed/24838476
Caspers KM, Romitti PA, Lin S, Olney RS, Holmes LB, Werler MM; National Birth Defects Prevention Study. Maternal periconceptional exposure to cigarette smoking and congenital limb deficiencies. Paediatr Perinat Epidemiol. 2013 Nov;27(6):509-20. doi: 10.1111/ppe.12075. Epub 2013 Jul 31. http://www.ncbi.nlm.nih.gov/pubmed/24134526
Horta BL, Victora CG, Menezes AM, Halpern R, Barros FC. Low birthweight, preterm births and intrauterine growth retardation in relation to maternal smoking. Paediatr Perinat Epidemiol. 1997 Apr;11(2):140-51. http://www.ncbi.nlm.nih.gov/pubmed/9131707
Hyland A, Piazza KM, Hovey KM, Ockene JK, Andrews CA, Rivard C, Wactawski-Wende J. Associations of lifetime active and passive smoking with spontaneous abortion, stillbirth and tubal ectopic pregnancy: a cross-sectional analysis of historical data from the Women's Health Initiative. Tob Control. 2014 Feb 26. doi: 10.1136/tobaccocontrol-2013-051458. [Epub ahead of print] http://www.ncbi.nlm.nih.gov/pubmed/24572626
Jones LL, Hashim A, McKeever T, Cook DG, Britton J, Leonardi-Bee J. Parental and household smoking and the increased risk of bronchitis, bronchiolitis and other lower respiratory infections in infancy: systematic review and meta-analysis. Respir Res. 2011 Jan 10;12:5. doi: 10.1186/1465-9921-12-5. http://www.ncbi.nlm.nih.gov/pubmed/21219618
Orton S, Bowker K, Cooper S, Naughton F, Ussher M, Pickett KE, Leonardi-Bee J, Sutton S, Dhalwani NN, Coleman T. Longitudinal cohort survey of women's smoking behaviour and attitudes in pregnancy: study methods and baseline data. BMJ Open. 2014 May 14;4(5):e004915. doi: 10.1136/bmjopen-2014-004915. http://www.ncbi.nlm.nih.gov/pubmed/24833689
Proskocil BJ, Sekhon HS, Clark JA, Lupo SL, Jia Y, Hull WM, Whitsett JA, Starcher BC, Spindel ER. Vitamin C prevents the effects of prenatal nicotine on pulmonary function in newborn monkeys. Am J Respir Crit Care Med. 2005 May 1;171(9):1032-9. Epub 2005 Feb 11. http://www.ncbi.nlm.nih.gov/pubmed/15709053
Radin RG, Hatch EE, Rothman KJ, Mikkelsen EM, Sørensen HT, Riis AH, Wise LA. Active and passive smoking and fecundability in Danish pregnancy planners. Fertil Steril. 2014 Apr 17. pii: S0015-0282(14)00259-3. doi: 10.1016/j.fertnstert.2014.03.018. [Epub ahead of print] http://www.ncbi.nlm.nih.gov/pubmed/24746741
Scholz R, Voigt M, Schneider KT, Rochow N, Hagenah HP, Hesse V, Straube S. Analysis of the German Perinatal Survey of the Years 2007-2011 and Comparison with Data From 1995-1997: Maternal Characteristics. Geburtshilfe Frauenheilkd. 2013 Dec;73(12):1247-1251. http://www.ncbi.nlm.nih.gov/pubmed/24771906