Effects of secondhand smoke on the birth weight of term infants and the demographic profile of Saudi exposed women
© Wahabi et al.; licensee BioMed Central Ltd. 2013
Received: 7 January 2013
Accepted: 11 April 2013
Published: 15 April 2013
Maternal exposure to tobacco smoke during pregnancy is associated with detrimental effects on the mother and the fetus including; impaired fetal growth, low birth weight and preterm delivery. In utero exposure to tobacco is implicated in the etiology of many adults’ diseases including obesity, diabetes and hypertension.
The objectives of this study were to evaluate the effects of Secondhand Tobacco Smoke (SHS) exposure on newborns’ anthropometric measurements and to compare the demographic profile of the women exposed to SHS to those who were not.
This is a retrospective cohort study investigating the effects of SHS during pregnancy on newborns’ anthropometry. Women who self-reported SHS exposure were compared with those not exposed. The primary outcomes were birth weight, newborn length and head circumference. Univariate analysis and multivariate regression analysis were performed. Adjusted differences with 95% confidence intervals were calculated.
Mothers exposed to SHS constituted 31% of the cohort. The mean birth weight of infants of exposed mothers was significantly lower by 35 g, 95% CI: 2–68 g, (P = 0.037) and the mean length was shorter by 0.261 cm, 95% CI 0.058-0.464 cm, (P = 0.012) compared to the infants of unexposed mothers. Women exposed to SHS, were younger, of lower parity and more likely to be illiterate than those who were not exposed in addition, exposed women were less likely to be primiparous.
The prevalence of exposure of Saudi pregnant women to SHS is high at 31% and it is associated with reduced birth weight, and shorter length of the newborn.
KeywordsSecond hand smoke Newborn anthropometry Saudi Arabia
Maternal smoking during pregnancy is associated with detrimental effects on the mother and the fetus including; impaired fetal growth, low birth weight, preterm delivery and increased neonatal and infant mortality rate [1–4]. Similar effects were reported for pregnancies exposed to secondhand smoke (SHS) . Moreover in-utero exposure to tobacco is rooted in the etiology of many adults’ diseases including obesity, diabetes and hypertension .
Similar to other reproductive health problems, there is paucity of information about the magnitude of tobacco smoking (both active and SHS) during pregnancy in Arab countries including the Kingdom of Saudi Arabia (KSA). The few published reports about tobacco smoking and SHS exposure during pregnancy are limited by either the small number of participants  or the difference in culture and social norms between geographical areas in the same country or between one country and another which limit generalization of results . Moreover some of these studies are outdated considering the major socioeconomic and life style changes in some counties such as the KSA, during last few decades .
The latest country survey in KSA showed that the prevalence of tobacco use among males is estimated at 24% and at 1% among females . Data about tobacco use in pregnancy was reported in one study . The study confirmed the adverse effect of SHS exposure on birth weight; however it was not designed to estimate the prevalence of SHS exposure in pregnancy or the maternal knowledge or attitude towards SHS .
KSA is one of the wealthiest countries in the Middle East; the Gross National per Capita Income is $22,750 in 2009 . Due to increased expenditure on healthcare there is rapid development in health services provision associated with improved socio-economic conditions. The Saudi Ministry of Health has implemented a national tobacco control program which is based on the WHO framework Convention for Tobacco Control and WHO-recommendation of the MPOWER strategies .
The implementation of any program aiming to reduce in-utero exposure to tobacco is dependent on the demographic profile of the pregnant women in the population and the nature of exposure to smoke, as being active smokers themselves or exposed to SHS.
Investigate the prevalence of tobacco use and SHS exposure among pregnant women in King Khalid University Hospital (KKUH)
Evaluate the effects of SHS exposure on the newborn biometric measurements (birth weight, length and head circumference)
Compare the demographic profile of the women exposed to SHS to those who were not exposed.
This is a retrospective cohort study, conducted at postnatal ward of KKUH in KSA. KKUH is a tertiary referral center; which includes a neonatal intensive care unit (NICU) and in vitro fertilization unit. The obstetrics department provides services for 3500–4000 deliveries per year.
The study was designed to investigate the effects of maternal exposure during pregnancy to SHS on the newborns’ anthropometric measurements (birth weight, length, head circumference) as primary outcomes, in addition we investigated the association of SHS with the following secondary outcomes; APGAR scores at 1 and 5 minutes, low birth weight (LBW) < 2.5 kg and admission to NICU.
Women with singleton pregnancy.
Term delivery (≥ 37 gestation week counted from the last menstrual period and/or early ultra-sound scan).
Women who did not smoke during the index pregnancy and were exposed to SHS (study group).
Women who did not smoke during the index pregnancy and were not exposed to SHS (control group).
We excluded from this study women with unknown smoking status.
Data were collected using a predesigned data collection sheet from women in the postnatal ward following delivery and before discharge from the hospital, by nurses who were trained to collect the data. Women who met the inclusion criteria and consented to the study were asked about their exposure to SHS which was defined as occurring when a woman, who did not smoke at all whilst pregnant, lived with a household member (husband, son, daughter or other relatives) who reported smoking during the index pregnancy. We did not assess occupational exposures. In addition participants were asked about their level of education (illiterate, schooling, university or above) and if they work for pay.
Data collected from the delivery records included gestational age at delivery, APGAR scores at 1 and 5 minutes, weight, length and head circumference of newborn and admission to NICU. Researchers who collected the data from the records were blinded to the smoking status of the mother. We compared the birth weight, length and head circumference, of infants of mothers who were exposed to SHS to those of mothers who were not exposed. In addition we compared the frequency of occurrence of LBW (< 2.5 kg) and APGAR scores at 1 and 5 minutes between the two groups.
The data collected from the antenatal records included; maternal age, gravidity, parity, maternal height and weight recorded during the first antenatal visit, from which, body mass index (BMI) was calculated according to the following equation; BMI = weight (kg)/height (m)2, in addition to antenatal events including the occurrence of preeclampsia defined as blood pressure ≥140/90 mm Hg after 20 weeks gestation and ≥ 0.3 g proteinuria/day, pregnancy induced hypertension defined as blood pressure ≥140/90 mm Hg after 20 weeks gestation without proteinuria and gestational diabetes (GDM) as per antenatal record diagnosis. These variables were extracted and analyzed as confounders due to their known influence on newborn anthropometry.
The ethical approval for the study was granted by the college of medicine, King Saud University Institutional Review Board, before the commencement of the study.
Statistical analyses were performed using SPSS, version 18.0 (SPSS Inc., Chicago, IL, USA). Descriptive statistics were computed for non-smoking pregnant women exposed and unexposed to SHS. Univariate analyses were performed to compare the birth weight, infant’s length and head circumference between the two groups as well as to evaluate the baseline characteristics between the groups which we considered as confounding factors. Chi-squared was used to compare dichotomous outcomes and Student’s t- test was used to compare continuous outcomes. Stepwise logistic regression models were used to adjust for potential confounders including maternal age, parity, BMI, GDM and gestational age (37–42 weeks). P value of < 0.05 was considered statistically significant.
During the study period there were 3766 deliveries of them 3 women self-reported active smoking and 3426 met the inclusion criteria and consented to the study. 1085 (31.7%) women self-reported exposure to SHS while 2341 (68.3%) did not report such exposure. The demographic characteristics of the women exposed and not exposed to SHS are shown in Table 1. Of the study population 3241 (94.6%) were Saudi. Women exposed to SHS, were younger, of lower parity and more likely to be illiterate than those who were not exposed. However exposed women were less likely to be primiparous.
The results of the pregnancy outcomes of the exposed and non-exposed women are shown in Table 2. Infants of women who were exposed to SHS had significantly less birth weight, and were significantly shorter than infants of non-exposed women. The mean head circumference of the infants of exposed mothers was smaller than that of infants of unexposed mother; however the difference did not reach statistical significance. Similarly, the frequency of low birth weight infants (<2.5 kg) was higher among infants of exposed mothers but the difference did not reach statistical significance.
Table 3 summarizes the results of the stepwise multivariate regression analysis for birth weight. After adjustment for confounding factors, the mean birth weight of infants of mothers exposed to SHS remained significantly lower by 35 g, 95% confidence interval (CI) 2-68 g, (p = 0.037), compared to the birth weight of infants of unexposed mothers (Table 3). Similarly, the mean length of infants of mothers exposed to SHS was significantly shorter compared to those of mothers who were not exposed, by 0.261cm, 95% CI, 0.058-0.464 cm, (p = 0.012) (Table 4).
We found that SHS constitutes a public health problem as more than 31% of women included in this study reported exposure to domestic SHS, with documented adverse effects on the birth weight and the newborn length.
Similar to maternal smoking during pregnancy, many studies confirmed that, exposure to SHS has adverse effects on the mother and the fetus [16, 17]. The suggested mechanisms for the reduced birth weight are the negative effects of nicotine and cotinine on the placental development and on its function of oxygen transfer to the fetus [18, 19]. Like other studies we did not find significant difference in the rate of LBW between infants of mothers exposed to SHS and those who were not [16, 17]. Nevertheless this finding does not disprove the adverse effects of smoking on the infants of normal birth weight as demonstrated by an earlier study, which showed that the mortality curve of infant exposed to smoking at any measure of birth weight is higher than for unexposed ones . We believe that the results of the effects of SHS exposure on the newborn anthropometric measurements, in this study, are reliable because we adjusted for multiple confounding factors which are known to influence the birth weight (Table 3). Unlike previous reports [21, 22] we consider GDM a confounding factor due to the reported high prevalence of the condition among Saudi pregnant women  which was further confirmed by the high prevalence of 15%, found in this study (Table 1).
The demographic profile of the pregnant women exposed to SHS in this study provides valuable information for future interventions to reduce SHS exposure in the household. It confirmed that most of the respondents to the survey were Saudis; hence any intervention based on the information from this study would be primarily directed towards the stable population of the country. Of paramount importance is the high level of literacy among the participants, which would facilitate the use of written and electronic information to increase the awareness and the knowledge about the hazards of SHS exposure in the household. However the high literacy level among the respondents of this study may not reflect the situation in rural areas of the country as differences in literacy levels were reported between urban and rural areas by other investigators .
Demographic characteristics of non-smoking women by exposure to SHS
Exposure to SHS
Total number 1085 Yes
Total number 2341 No
Maternal age (years)
28.83 ± 6.11
29.60 ± 6.20
2.78 ± 2.08
3.02 ± 2.20
3.31 ± 2.62
3.53 ± 2.67
29.69 ± 6.14
29.48 ± 5.98
Gestational diabetes mellitus
Pregnancy induced hypertension
Level of education
University and above
In this study only three women reported active smoking during pregnancy while more than 31% reported SHS and more than 80% of the participants reported their husbands as the main source of SHS in the household. These results are consistent with the findings from 31 developing countries . The implications of these results are that any intervention for reducing SHS exposure in the household should be directed to both parents, rather than to the mother only, and that interventions implemented for smoking cessation may indirectly reduce the exposure to SHS by decreasing the number of smoking males.
The results of the perinatal outcomes in non-smoking women by exposure to SHS
Exposure to SHS
Total number (1085) Yes
Total number (2341) No
3.15 ± 0.46
3.21 ± 0.46
49.62 ± 3.09
49.87 ± 2.48
34.05 ± 1.59
34.14 ± 1.73
Apgar at 5 min
8.92 ± 0.64
8.91 ± 0.66
Apgar at 1 min
7.73 ± 0.86
7.75 ± 0.82
Low birth weight (<2500 gms)
Regression model for birth weight at term (37 weeks or more)
0.086 to 0.113
0.007 to 0.012
0.002 to 0.009
Level of education
0.028 to 0.88
0.022 to 0.11
-0.068 to -0.002
Although public health interventions such as mass media campaigns, legislative banning of smoking in public places and increasing tobacco prices and taxes were proven to be effective in reducing the prevalence of tobacco smoking and SHS exposure in public places, such interventions were not only ineffective in reducing exposure to SHS in the household  but might even increase the risk of exposure to SHS at home . Similarly the use of an air cleaner was proven to be effective in reducing the concentration of particulate matter with improvement in clinical symptoms of asthmatic children; however this intervention did not reduce exposure to SHS .
Regression model for baby’s length at term (37 weeks or more)
Recently, the use of personalized data of the house air quality has been investigated and proven effective in motivating smoking mothers, with small children, to change their smoking behavior with positive impact on the air quality of the house [33, 34].
Our study has confirmed the high prevalence of exposure of pregnant women to SHS and it documented a biological harmful effect of SHS on the newborn in a Saudi community; in addition it has outlined the demographic profile of the pregnant Saudi women who were exposed to SHS. The results of this study would help in planning an effective program for reducing exposure to SHS for pregnant women in KSA.
We are aware of the limitations of this study including that the exposure to SHS was based on women’s self-report without the use of biomarker to verify exposure. Another limitation is that we did not quantify the exposure to SHS by the number of hours the mother exposed; or the number of smokers in the in the family, both factors were proven to increase the health risks of SHS  hence we did not report a dose response relationship between exposure to SHS and pregnancy outcomes; however due to the self-reported design of the study and the possibility of recall bias, a dose response might not have been verified.
The prevalence of exposure of Saudi pregnant women to SHS is high at 31% and it is associated with reduced birth weight, and shorter length of the newborn.
We thank the Deanship of Scientific Research; King Saud University for funding this study and we acknowledged the assistance of Mrs. Margaret Taiwo and the nurses of the postnatal ward of KKUH for their participation in the data collection.
This study was funded by grant No. RGP-VPP-149 from the Deanship of Scientific Research, King Saud University, Riyadh, KSA.
- Hackshaw A, Rodeck C, Boniface S: Maternal smoking in pregnancy and birth defects: a systematic review based on 173 687 malformed cases and 11.7 million controls. Hum Reprod Update. 2011, 17: 589-604. 10.1093/humupd/dmr022.View ArticlePubMedPubMed CentralGoogle Scholar
- Hayashi K, Matsuda Y, Kawamichi Y, Shiozaki A, Saito S: Smoking during pregnancy increases risks of various obstetric complications: a case-cohort study of the Japan Perinatal Registry Network database. J Epidemiol. 2011, 21: 61-66. 10.2188/jea.JE20100092.View ArticlePubMedPubMed CentralGoogle Scholar
- Chiolero A, Bovet P, Paccaud F: Association between maternal smoking and low birth weight in Switzerland: the EDEN study. Swiss Med Wkly. 2005, 135: 525-530.PubMedGoogle Scholar
- Basso O, Wilcox AJ, Weinberg CR: Birth weight and mortality: causality or confounding?. Am J Epidemiol. 2006, 164: 303-311. 10.1093/aje/kwj237.View ArticlePubMedGoogle Scholar
- Crane JM, Keough M, Murphy P, Burrage L, Hutchens D: Effects of environmental tobacco smoke on perinatal outcomes: a retrospective cohort study. BJOG. 2011, 118: 865-871. 10.1111/j.1471-0528.2011.02941.x.View ArticlePubMedGoogle Scholar
- Bergen HT: Exposure to smoke during development: fetal programming of adult disease. Tob Induc Dis. 2006, 3: 5-16. 10.1186/1617-9625-3-2-5.View ArticlePubMedPubMed CentralGoogle Scholar
- Wadi MA, Al-Sharbatti SS: Relationship between birth weight and domestic maternal passive smoking exposure. East Mediterr Health J. 2011, 17: 290-296.PubMedGoogle Scholar
- Chaaya M, Awwad J, Campbell OM, Sibai A, Kaddour A: Demographic and psychosocial profile of smoking among pregnant women in Lebanon: public health implications. Matern Child Health J. 2003, 7: 179-186. 10.1023/A:1025136421230.View ArticlePubMedPubMed CentralGoogle Scholar
- Rashid M, Rashid H: Passive maternal smoking and pregnancy outcome in a Saudi population. Saudi Med J. 2003, 24: 248-253.PubMedGoogle Scholar
- World Health Organization Report on the Global Tobacco Epidemic: 2011, Country Profile Saudi Arabia: , http://www.who.int/tobacco/surveillance/policy/country_profile/sau.pdf Date of access Nov 2012
- World Health Organization: 2009, Country profile Saudi Arabia: , http://www.who.int/countries/sau/en/index.html Date of access Nov 2012
- The World Health Organization: MPOWER. 2012, A policy Package to Reverse The Tobacco Epidemic: , http://www.who.int/tobacco/mpower/mpower_english.pdf Date of access Nov 2012Google Scholar
- Windham GC, Eaton A, Hopkins B: Evidence for an association between environmental tobacco smoke exposure and birthweight: a meta-analysis and new data. Paediatr Perinat Epidemiol. 1999, 13: 35-57. 10.1046/j.1365-3016.1999.00150.x.View ArticlePubMedGoogle Scholar
- Wahabi HA, Esmaeil SA, Fayed AA, Al-Shaikh G, Alzeidan RA: Pre-existing diabetes mellitus and adverse pregnancy outcomes. BMC Res Notes. 2012, 5: 496-10.1186/1756-0500-5-496.View ArticlePubMedPubMed CentralGoogle Scholar
- WHO Obesity: World Health Organization. 2000, Geneva Switzerland World Health Oganization; 2000 WHO technical eport series 894: Obesity: preventing and managing the golbal epidemic, http://www.who.int/nutrition/publications/obesity/WHO_TRS_894/en/ Date of access Nov 2012 2000Google Scholar
- Ward C, Lewis S, Coleman T: Prevalence of maternal smoking and environmental tobacco smoke exposure during pregnancy and impact on birth weight: retrospective study using Millennium Cohort. BMC Public Health. 2007, 7: 81-10.1186/1471-2458-7-81.View ArticlePubMedPubMed CentralGoogle Scholar
- Salmasi G, Grady R, Jones J, McDonald SD: Environmental tobacco smoke exposure and perinatal outcomes: a systematic review and meta-analyses. Acta Obstet Gynecol Scand. 2010, 89: 423-441. 10.3109/00016340903505748.View ArticlePubMedGoogle Scholar
- Romani F, Lanzone A, Tropea A, Tiberi F, Catino S, Apa R: Nicotine and cotinine affect the release of vasoactive factors by trophoblast cells and human umbilical vein endothelial cells. Placenta. 2011, 32: 153-160. 10.1016/j.placenta.2010.11.010.View ArticlePubMedGoogle Scholar
- Zdravkovic T, Genbacev O, McMaster MT, Fisher SJ: The adverse effects of maternal smoking on the human placenta: a review. Placenta. 2005, 26 (Suppl A): 81-86.View ArticleGoogle Scholar
- Wilcox AJ: On the importance–and the unimportance–of birthweight. Int J Epidemiol. 2001, 30: 1233-1241. 10.1093/ije/30.6.1233.View ArticlePubMedGoogle Scholar
- Hanke W, Sobala W, Kalinka J: Environmental tobacco smoke exposure among pregnant women: impact on fetal biometry at 20–24 weeks of gestation and newborn child's birth weight. Int Arch Occup Environ Health. 2004, 77: 47-52. 10.1007/s00420-003-0475-0.View ArticlePubMedGoogle Scholar
- Hegaard HK, Kjaergaard H, Moller LF, Wachmann H, Ottesen B: The effect of environmental tobacco smoke during pregnancy on birth weight. Acta Obstet Gynecol Scand. 2006, 85: 675-681. 10.1080/00016340600607032.View ArticlePubMedGoogle Scholar
- Bhanji S, Andrades M, Taj F, Khuwaja AK: Factors related to knowledge and perception of women about smoking: a cross sectional study from a developing country. BMC Womens Health. 2011, 11: 16-10.1186/1472-6874-11-16.View ArticlePubMedPubMed CentralGoogle Scholar
- Wipfli H, Avila-Tang E, Navas-Acien A, Kim S, Onicescu G, Yuan J: Secondhand smoke exposure among women and children: evidence from 31 countries. Am J Public Health. 2008, 98: 672-679. 10.2105/AJPH.2007.126631.View ArticlePubMedPubMed CentralGoogle Scholar
- Barbour B, Salameh P, Ziadeh F: [Smoking among Lebanese mothers: knowledge, attitudes and practices]. East Mediterr Health J. 2006, 12: 405-416.PubMedGoogle Scholar
- Helgason AR, Lund KE: Environmental tobacco smoke exposure of young children–attitudes and health-risk awareness in the Nordic countries. Nicotine Tob Res. 2001, 3: 341-345. 10.1080/14622200110050420.View ArticlePubMedGoogle Scholar
- Mills LM, Semple SE, Wilson IS, Maccalman L, Amos A, Ritchie D: Factors influencing exposure to secondhand smoke in preschool children living with smoking mothers. Nicotine Tob Res. 2012Google Scholar
- Callinan JE, Clarke A, Doherty K, Kelleher C: Legislative smoking bans for reducing secondhand smoke exposure, smoking prevalence and tobacco consumption. Cochrane Database Syst Rev. 2010, CD005992:Google Scholar
- Yao T, Lee AH, Mao Z: Potential unintended consequences of smoke-free policies in public places on pregnant women in China. Am J Prev Med. 2009, 37: S159-S164. 10.1016/j.amepre.2009.05.014.View ArticlePubMedPubMed CentralGoogle Scholar
- Butz AM, Matsui EC, Breysse P, Curtin-Brosnan J, Eggleston P, Diette G: A randomized trial of air cleaners and a health coach to improve indoor air quality for inner-city children with asthma and secondhand smoke exposure. Arch Pediatr Adolesc Med. 2011, 165: 741-748. 10.1001/archpediatrics.2011.111.View ArticlePubMedGoogle Scholar
- Loke AY, Lam TH: A randomized controlled trial of the simple advice given by obstetricians in Guangzhou, China, to non-smoking pregnant women to help their husbands quit smoking. Patient Educ Couns. 2005, 59: 31-37. 10.1016/j.pec.2004.08.018.View ArticlePubMedGoogle Scholar
- Priest N, Roseby R, Waters E, Polnay A, Campbell R, Spencer N: Family and carer smoking control programmes for reducing children's exposure to environmental tobacco smoke. Cochrane Database Syst Rev. 2008, CD001746:Google Scholar
- Wilson I, Semple S, Mills LM, Ritchie D, Shaw A, O'Donnell R: REFRESH--reducing families' exposure to secondhand smoke in the home: a feasibility study. Tob Control. 2012Google Scholar
- Wilson IS, Ritchie D, Amos A, Shaw A, O'Donnell R, Mills LM: 'I'm not doing this for me': mothers' accounts of creating smoke-free homes. Health Educ Res. 2012Google Scholar
- The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2458/13/341/prepub