The European Journal of Public Health Advance Access originally published online on August 10, 2005
The European Journal of Public Health 2005 15(6):613-614; doi:10.1093/eurpub/cki052
Smoking |
Periconceptional smoking and male : female ratio of newborns
Fabio Parazzini1,2, Liliane Chatenoud1, Cristina Maffioletti2, Francesca Chiaffarino1 and Donatella Caserta3
1 Istituto di Ricerche Farmacologiche ‘Mario Negri’, Milano, Italy
2 Prima Clinica Ostetrico Ginecologica, Università di Milano, Milano, Italy
3 Clinica Ostetrico Ginecologica, Università dell'Aquila, Aquila, Italy
Correspondence: Fabio Parazzini, Istituto di Ricerche Farmacologiche ‘Mario Negri’, Via Eritrea 62, 20157 Milano, Italy, tel: +39 02 390141, fax: +39 02 33200231, e-mail: parazzini{at}marionegri.it
Received March 31, 2004, accepted July 22, 2004
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Abstract |
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We have analysed data collected on 1962 women who gave birth at 37 or more weeks of gestation to health infants (excluding those with a low birth weight and twins). In comparison with non-smoking parents, the odds ratio (OR) of being male was lower than unity for offsprings of both smoking parents, but no clear relationship however emerged between the risk of giving birth to a male, and the number of cigarettes smoked per day.
Keywords: smoking, male : female ratio, preconceptional
Astudy conducted in Japan on 11 815 births has suggested that smoking habits of parents around the time of conception affect the likelihood of the offspring being male or female.1 In particular, the frequency of male offspring was lower when either one or both of the parents smoked more than 20 cigarettes per day, compared with couples in which neither of the parents smoked. This finding may explain the epidemiological observation of a lowering male to female ratio reported in some countries.2,3 In etiopathogenetic terms it has been suggested that exposure to toxic agents may affect sperm motility, which can be more marked for XY spermatozoas.4 Other studies have analysed the relation between smoking and male : female rate, showing controversial results.5,6
In order to offer further information on the issue, we have analysed data collected in the framework of case–control studies conducted in Italy.7,8
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Methods |
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We have analysed data collected on women in the control group of a case–control study on risk factors for several pregnancy related diseases. This group included women who gave birth at 37 or more weeks of gestation to healthy infants (excluding those with a low birth weight and twins).
The present analysis is based on infants delivered by 1962 women (median age 30 years, range 14–45) who gave birth on randomly selected days at the Clinica Luigi Mangiagalli (the largest obstetric hospital in Milan) and a network of obstetric hospitals in Milan and at the Obstetric Clinic of University of Verona.7,8
During their stay in hospital, the women were interviewed by trained interviewers. Information was collected about sociodemographic characteristics and habits including smoking during periconceptional period. Women were also asked about smoking habits of the father of newborn during the periconceptional period; thus father's smoking habits were reported by the women.
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Results |
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Table 1 shows the distribution of male and female newborns, the male : female ratios and the odds ratio of being male, according to periconceptional smoking habits of the parents.
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In comparison with non-smoking parents, the odds ratio of being male was lower than unity for offspring of women smoking more than 20 cigarettes/day and non-smoking fathers and for offsprings of both-smoking parents. No clear relationship emerged, however, between the risk of giving birth to a male and number of cigarettes smoked per day. For example, in comparison with non-smoking parents, the odds ratio of giving birth to a male was 0.79 for the couple in which the mother smoked 1–19 cigarettes and the father more than 20 cigarettes, and 0.92 for the couples in which both the mother and the father smoked more than 20 cigarettes/day. None of the estimated odds ratios, however, were statistically significant.
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Discussion |
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The results of this analysis give little support to the hypothesis that periconceptional smoking of the parents may affect the male : female ratio of the offspring. No clear relationship emerged with regard to number of cigarettes smoked per day and, in general, the limited power of the analysis does not provide the opportunity of better analysing the effect of various levels of exposure to smoking.
Key point
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References |
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1 Fukuda M, Fukuda K, Shimizu T, Andersen CY, Byskov AG. Parental periconceptional smoking and male: female ratio of newborn infants. Lancet 2002;359:1407–8.[CrossRef][ISI][Medline]
2 Parazzini F, La Vecchia C, Levi F, Franceschi S. Trends in male : female ratio among newborn infants in 29 countries from five continents. Hum Reprod 1998;13:1394–6.
3 Parazzini F, Chatenoud L, Belloni G, et al. Selected food intake and risk of multiple pregnancies. Hum Reprod 2001;16:370–3.
4 Sakamoto M, Nakano A, Akagi H. Declining Minamata male birth ratio associated with increased male fetal death due to heavy methylmercury pollution. Environ Res 2001;87:92–7.[Medline]
5 Mills JL, England L, Granath F, Cnattingius S. Cigarette smoking and the male-female sex ratio. Fertil Seril 2003;79:1243–5.
6 Obel C, Henriksen TB, Hedegaard M, Bech BH, Wisborg K, Olsen J. Periconceptional smoking and the male to female ratio in the offspring—re-assessment of a recently proposed hypothesis. Int J Epidemiol 2003;32:470–1.
7 Parazzini F, Chatenoud L, Tozzi L, Benzi G, Dal Pino D, Fedele L. Determinants of risk of spontaneous abortions in the first trimester of pregnancy. Epidemiology 1997;8:681–3.[CrossRef][ISI][Medline]
8 Parazzini F, Chatenoud L, Di Cintio E, La Vecchia C, Benzi G, Fedele L. Alcohol consumption is not related to fertility in Italian women. Br Med J 1999;318:397.
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