Maternal cigarette smoking, breast-feeding, and respiratory tract infections in infancy. A matched-pairs study

Does maternal smoking have a negative physiological effect on breastfeeding? The epidemiological evidence

BACKGROUND

Women who smoke are less likely to breastfeed their children than nonsmokers. It is thought that nicotine has a negative effect on breastmilk supply by suppressing prolactin levels. The aim of this review was to assess the epidemiological evidence that maternal smoking has a negative physiological effect on breastfeeding.

METHODS

The following data sources were searched: The Cochrane Library, Medline, CINAHL, Current Contents, Psychinfo, Sociological Abstracts and the Lactation Resource Centre (Australian Breastfeeding Association) using the key words "smoking" and "breastfeeding" or "infant feeding." The Journal of Human Lactation and Birth were hand searched.

RESULTS

Women who smoke are less likely to intend to breastfeed, less likely to initiate breastfeeding, and likely to breastfeed for a shorter duration than nonsmokers. Several studies have found a dose-response relationship between the number of cigarettes smoked each day and breastfeeding intention, initiation, and duration that persists after adjusting for confounding factors. In some population groups a high proportion of smokers breastfeed successfully.

CONCLUSIONS

The association between maternal smoking and lack of breastfeeding is consistent across different study designs in a range of countries. Given that women who smoke are less likely to intend to breastfeed, however, it cannot be assumed that the relationship between smoking and duration of breastfeeding is a physiological one. If smoking had a consistent negative physiological effect on lactation, one would not expect to see such wide variations in breastfeeding rates among women who smoke. Therefore, it is likely that psychosocial factors are largely responsible for the lower rates of breastfeeding found in women who smoke compared with those who do not.

Breast-feeding in Iceland. Predictive factors and effects of interventive measures

The aim of this study was to analyse how long babies born in Akureyri district in 1990 were breast-fed, compared with babies born in 1985. Possible predictive factors for the length of breast-feeding were studied by univariate and multivariate analyses. From 1985 to 1990, the proportion of infants exclusively breast-fed at the age of 3 months increased from 57% to 70% (p < 0.01) and for those breast-fed exclusively or partially, from 67% to 83% (p < 0.01). By 1990, 64% of all babies were breast-fed at the age of 6 months, compared with 43% in 1985 (p < 0.01). The factor with the strongest correlation with a long breast-feeding period was a well educated father. Other factors correlated with the duration of breast-feeding were the mother's age, number of previous children, attending a maternity course, and being a non-smoker. It is concluded that real beneficial changes regarding the duration of breast-feeding in Iceland have been observed during the last decade, but the objectives of the preventive measures recommended by health authorities have not yet been reached.

Factors adversely associated with breast feeding in New Zealand

Control data from 1529 infants studied in a multicentre case-control study of sudden infant death in New Zealand were analysed to identify factors that might hinder the establishment and duration of breast feeding. Although 1300 infants (85%) were exclusively breast-fed at discharge from the obstetric hospital, this fell to 940 (61%) by 4 weeks. Logistic regression was used to identify factors that might adversely influence breast feeding 'at discharge', 'at 4 weeks' and the overall 'duration' of breast feeding. When adjusted for confounding factors, not exclusive breast feeding 'at discharge' was significantly associated with: twin pregnancy, being a Pacific Islander, mother not bedsharing, subsequent dummy use, birthweight less than 2500 g, heavy maternal smoking, not attending antenatal classes and mother less than 20 years old at first pregnancy. Mothers smoking more than 20 cigarettes a day were nearly twice as likely to not exclusively breast feed on discharge compared to those who did not smoke. A 'dose response' was apparent with the heaviest smokers having the least likelihood of establishing exclusive breast feeding. Being exclusively breast-fed at discharge but not 'at 4 weeks' was associated with: twin pregnancy, admission to a neonatal intensive care unit, subsequent dummy use and not being married. A shorter overall 'duration' of breast feeding was associated with maternal smoking, subsequent dummy use, mother not bedsharing, twin pregnancy, mother less than 20 years old at first pregnancy, low occupational status and not attending antenatal classes. These effects persisted when social and demographic factors, including birthweight, were taken into account.(ABSTRACT TRUNCATED AT 250 WORDS)

Pregnancy--a golden opportunity for promoting the cessation of smoking?

OBJECTIVE

To investigate whether daily-smoking pregnant women are more motivated to reduce their cigarette consumption than daily-smoking non-pregnant women.

DESIGN

Prospective study with self-administered questionnaires at inclusion and 18 months later.

SETTING

116 general practitioners in western Norway.

SUBJECTS

83 pregnant and 107 non-pregnant women.

MAIN OUTCOME MEASURES

Non-anonymous questionnaires focusing on smoking habits and attitudes to smoking cessation.

RESULTS

Pregnant women were more often encouraged to stop smoking by their partners than non-pregnant women (p < 0.01). More pregnant than non-pregnant women totally agreed that their GP should try to motivate their patients to stop smoking (p < 0.001). Pregnant women also predicted that they would be non-smokers in five years more often than non-pregnant women (p < 0.001). Eighteen months later no such difference was found. A reduced cigarette consumption, verified by serum thiocyanate, was found among women early in pregnancy. The reduced consumption found later in pregnancy and the first year after delivery may be explained to some extent by systematic underreporting. At the end of the study eight per cent of both pregnant and non-pregnant women had stopped smoking.

CONCLUSION

We need to develop strategies for utilizing the unique opportunity which pregnancy provides for the motivation of cessation of smoking.

Upper airway infections in preschool children--frequency and risk factors

OBJECTIVE

To estimate the frequency of upper respiratory tract infections (URTI) over a three month period and possible risk factors in the social surroundings, daily routines and health history.

DESIGN

A retrospective epidemiological survey by means of questionnaires.

SETTING

Gardabaer, a small town, ten km south of Reykjavík, Iceland.

PARTICIPANTS

All children in Gardabaer, six months to six years old (n = 555).

MAIN OUTCOME MEASURE

Number of URTI and possible risk factors.

RESULTS

The response rate was 81.8%. The most common infections were common cold (n = 345), acute otitis media (n = 82), sore throat (n = 75), and bronchitis (n = 13). The mean frequency of URTI during the previous three months was 2.2 in boys and 1.7 in girls (p < 0.01). Log-linear regression analysis showed that the predicted number of URTI was 1.9 higher if the child was attending day care, and that the number of URTI increased by 1.015 with each month until the age of 24 months, but decreased after that by 0.985.

CONCLUSIONS

The major factors which affect the frequency of URTI are: age, sex, family history of frequent URTI, asthma, allergy, and the form of day care. Measures to reduce URTI could involve prospective intervention studies on the form of day care.

Maternal cigarette smoking, breast-feeding, and respiratory tract infections in infancy. A population-based cohort study

This population-based study comprised 192 mothers and their infants; 58 mothers were smokers and 134 non-smokers. At the 18-month infant check-up at the child health clinic, mothers were questioned about the length of the breast-feeding period, both exclusively breast-feeding and overall breast-feeding time. The numbers of antibiotic-treated respiratory tract infections (RTIs) during the first year of life were noted during a scrutiny of records at the district physician's surgery and child health clinic of the Health Centre, and at the paediatric and ENT departments of the Central Hospital. We were unable to find any connection between the duration of breast-feeding and the number of antibiotic-treated RTIs in the infants. This applied to both exclusively breast-feeding period and overall breast-feeding period. Further, it was shown that infants of smokers were affected by RTIs more often than those of non-smokers, the incidence figures being 1.16 vs. 0.76 antibiotic courses per infant and year, respectively. Moreover, infants of smokers were breast-fed for a shorter period than those of non-smokers, the mean values being 3.3 vs. 4.3 months, respectively, for the period of exclusively breast-feeding, and 5.0 vs. 7.2 months, respectively, for the overall breast-feeding period.