|Year : 2018 | Volume
| Issue : 4 | Page : 728-733
Tobacco use, exposure to second-hand smoke among pregnant women and their association with birth weight: A retrospective cohort study
Amrutha Varshani Krishnamurthy1, Palanivel Chinnakali1, Gowri Dorairajan2, Shanthosh Priyan Sundaram1, Gokul Sarveswaran1, Midhune Sivakumar1, Kishore Krishnamoorthy1, Hemalatha Dayalane1, Vijay Sinouvassan1
1 Department of Preventive and Social Medicine, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
2 Department of Obstetrics and Gynecology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
|Date of Web Publication||4-Sep-2018|
Ms. Amrutha Varshani Krishnamurthy
Omkar, 91 and 92, Second Cross, Vasan Nagar, Lawspet, Puducherry - 605 008
Source of Support: None, Conflict of Interest: None
Background: There is paucity of studies on prevalence of SHS among pregnant women and its association with low birth weight (LBW). Objectives: The study was designed to determine the proportion of tobacco use, exposure to second hand smoke among pregnant women and their association with LBW. Materials and Methods: A Retrospective cohort study was conducted from March–June 2017 among 1043 pregnant women admitted for delivery in the Department of Obstetrics and Gynecology, JIPMER. Socio-demographic and obstetric characteristics, tobacco use and exposure to SHS during pregnancy were assessed by interviews. Birth weight of the baby was also extracted. Data was analysed using STATA v12. Univariate analysis was used to assess the association of socio-demographic, obstetric characteristics and exposure to SHS with LBW. Results: Out of 1043 pregnant women, the mean age was 25 (±3.9) years. More than half (57.4%) of women were primigravida. The proportion of women exposed to SHS during pregnancy was 69.9% (95% CI: 67.0-72.6) among which 24% of the women belonged to family, where family members were smokers. Only four had ever used tobacco in the past. However, none used any form of tobacco during pregnancy. LBW was present in 21.4% of the babies. There was no association between exposure to SHS and LBW [PR:0.98 (95% CI:0.71-1.35)]. Conclusion: The study shows that there was no significant association between the SHS exposure of pregnant women and low birth weight.
Keywords: Low birth weight, retrospective cohort, second-hand smoke
|How to cite this article:|
Krishnamurthy AV, Chinnakali P, Dorairajan G, Sundaram SP, Sarveswaran G, Sivakumar M, Krishnamoorthy K, Dayalane H, Sinouvassan V. Tobacco use, exposure to second-hand smoke among pregnant women and their association with birth weight: A retrospective cohort study. J Family Med Prim Care 2018;7:728-33
|How to cite this URL:|
Krishnamurthy AV, Chinnakali P, Dorairajan G, Sundaram SP, Sarveswaran G, Sivakumar M, Krishnamoorthy K, Dayalane H, Sinouvassan V. Tobacco use, exposure to second-hand smoke among pregnant women and their association with birth weight: A retrospective cohort study. J Family Med Prim Care [serial online] 2018 [cited 2019 Sep 17];7:728-33. Available from: http://www.jfmpc.com/text.asp?2018/7/4/728/240405
| Introduction|| |
The World Health Organization (WHO) estimates that tobacco use is responsible for almost six million deaths each year – one death every 6 s and is projected to rise to eight million deaths per year by 2030. Tobacco comes in smoked and smokeless forms, both of which have been shown to cause adverse outcomes in pregnant women and their fetuses. The harms of tobacco use in pregnancy are not limited to smoked tobacco products only. Evidence suggests that infants born to women who use smokeless tobacco in pregnancy have a higher risk of several adverse outcomes such as stillbirth, preterm birth, and low birth weight.,, In addition, maternal exposure to second-hand smoke (SHS) in pregnancy has also been associated with a modest reduction in birth weight and can increase the risk of low birth weight (<2500 g) by 22%.
The WHO in its “Recommendations for the prevention and management of tobacco use and SHS exposure in pregnancy” emphasizes the need for effective screening by health-care providers for tobacco use among pregnant women during routine antenatal visits. The WHO recommendations released in the year 2013 also highlighted the paucity of studies on the prevalence (burden) and interventions for tobacco and second and smoke in low- and middle-income countries. The third round of the National Family Health Survey 3 conducted during 2005–2006 reported 8.5% of pregnant women use any form of tobacco (smoke or smokeless) during pregnancy, as high as 13% in Jharkhand., These estimates are community-based and a decade old; current assessment of burden among pregnant women attending hospitals is required to plan for interventions during their hospital visits. Hence, this study was conducted among pregnant women with period of gestation (POG) more than 28 weeks to determine the burden of tobacco use and exposure to SHS at home or workplace and to assess whether tobacco use and exposure to SHS are associated with low birth weight in a tertiary care setting.
| Materials and Methods|| |
A retrospective cohort study was conducted among women who attended for Postnatal visit in the Department of Obstetrics and Gynecology, JIPMER, in the months of May and June 2017. Women who delivered with POG more than 28 weeks and admitted for delivery were included. Pregnant women with multiple pregnancies were included in the study for determining the proportion reporting tobacco use anytime during the antenatal period and to determine the proportion exposed to SHS at home or workplace but was excluded from the association with low birth weight.
Sample size and sampling technique
Based on the proportion of pregnant women exposed to SHS as 10.5%, assuming alpha error of 5%, absolute precision of 2%, a total of 900 pregnant women were required for the study. Since the study included follow-up after delivery, a sample size of about 1000 was decided considering 10% loss to follow-up/nonresponse. All the eligible pregnant women were included in the study.
After approval by scientific and ethics committees, women attending the Postnatal visit in the Department of Obstetrics and Gynecology were interviewed by the trained interviewer. The senior professor supervised the sanctity of the data collection. Sociodemographic and obstetric characteristics such as age, education of the pregnant women, education of husband, and employment status of pregnant women during antenatal period, parity, previous abortions, and family income were obtained using pretested, structured pro forma, which was prepared by the researcher. Information on tobacco use and exposure to SHS and their frequency was also obtained. Information on medical disorders during pregnancy, hemoglobin levels, and birth weight was obtained from the individual patient case records after delivery. Apart from birth weight, information on preterm birth and stillbirth was also extracted.
Tobacco use was defined as reporting of any tobacco use (smoke or smokeless form) anytime during antenatal period. Exposure to SHS was defined as positive response to the question “Were you ever exposed to passive smoking during your pregnancy?”
Low birth weight was defined by the WHO as weight at birth of <2500 g.
Sociodemographic and obstetric characteristics
The sociodemographic and obstetric characteristics were age, education of the pregnant women, education of husband, and employment status of pregnant women during antenatal period, parity, previous abortions (yes/no), high-risk pregnancy/comorbidity (yes/no), and per capita income.
The outcome variables were tobacco use (yes/no), exposure to SHS (yes/no), place of exposure to SHS (home/workplace), frequency of tobacco use/exposure to SHS, duration of exposure, and low birth weight (defined as birth weight <2.5 kg).
The cofounding variables were age, parity, education of pregnant women and husband, hemoglobin levels, and weight of the pregnant women in the third trimester (crude proxy measures for dietary intake).
Data were single entered in EpiData Manager Software version 18.104.22.168 (EpiData Association, Odense, Denmark). Sociodemographic and demographic characteristics are expressed as percentages. Exposure to SHS is expressed as proportions with 95% confidence intervals (CIs). Birth weight is expressed as mean (standard deviation), and it is categorized as low birth weight (<2500 g) and normal birth weight (≥2500 g) for univariate analysis. To assess the association of tobacco use and exposure to SHS with low birth weight, unadjusted prevalence ratio (PR) was calculated along with 95% CI and P value. P < 0.05 was considered as statistically significant. Analysis was done using Stata software version 12.0 (StataCorp. 2011. Stata Statistical Software: Release 12. College Station, TX: StataCorp LP) by a professional trained in the corresponding software.
Institute Ethical committee approval was obtained before the starting the study. Informed consent was obtained from the study participants. After the interviews, the adverse health effects of tobacco and SHS were explained to the study participants.
| Results|| |
Sociodemographic characteristics of the participants
A total of 1043 pregnant women who were more than 28 weeks of gestation and admitted for delivery were included in the study. Mean age of the study participants was 25 ± 3.9 years with a minimum of 18 years and maximum of 46 years. About two-third of the participants had completed higher secondary and above and 4% of the mothers were illiterate. However, only 8% of the mothers were employed and the rest (92%) of the mothers were homemakers. Among the spouse, about half (46%) of them were higher secondary and above and 5% of the spouses were illiterate. Nearly four-fifth (78%) of the participants were from rural area. The women who were illiterate had significantly higher chance of having babies with low birth weight when compared to those who are graduate or more (PR: 2.78 [95% CI: 1.40–5.54]). There was no significant association between other sociodemographic characteristics and low birth weight of the infants of women who were admitted for delivery [Table 1].
|Table 1: Association of sociodemographic characteristics with low birth weight infants among pregnant women attending a tertiary care center, Puducherry, 2017 (n=1043)|
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Obstetric characteristics of the pregnant women
[Table 2] shows that 57.4% of the mothers who were admitted for delivery were primi and 0.9% of them were grandmultiparous women. About 4% of women had two or more abortions. Mean hemoglobin was found to be 9.9 (±1.8) g% with a minimum of 4.6 g% and a maximum of 14.7 g%. More than half of the participants (54%) were moderately anemic and five women had severe anemia. High-risk pregnancy was present in 34% of the participants. Women who are multigravida were having lesser chance of having low birth weight babies when compared to primi women (PR: 0.86 [95% CI: 0.76–0.97]).
|Table 2: Association of obstetric characteristics with low birth weight infants among pregnant women attending a tertiary care center, Puducherry, 2017 (n=1043)|
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Characteristics of newborn
The mean birth weight was 2.8 (±0.5) kg with 21.4% of the babies being low birth weight. More than half (52%) of the babies were of male gender [Table 3].
|Table 3: Association of infant characteristics with low birth weight infants among pregnant women attending a tertiary care center, Puducherry, 2017 (n=1043)|
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Second-hand smoke exposure and their characteristics among pregnant women during pregnancy
The proportion of women exposed to SHS during pregnancy was 69.9% (95% CI: 67.0–72.6) among which one-fourth (23.68% [95% CI: 21.1–26.4]) of the women belonged to family, where family members were smokers. Only four  had ever used tobacco in the past (3 smoke for and 1 smokeless form). However, no woman used any form of tobacco during pregnancy. Among women exposed to SHS during pregnancy, 78% of them were exposed at public place and 14% of women were exposed to SHS at their home. Duration of exposure was ≤10 days in more than half (54%) of the participants, and 19% of the participants were exposed to SHS for more than 6 months during the pregnancy. Majority (74%) of the participants were exposed during the third trimester. Newborns of female sex had higher odds of being low birth weight when compared to males (PR: 1.39 [95% CI: 1.04–1.88]). There was a mean difference of 51 g in birth weight between the babies born to mothers who were exposed to SHS during pregnancy as compared to those who were not exposed it, and it was not statistically significant (PR: 0.98 [95% CI: 0.71–1.35]). Similarly, there was no significant difference in birth weight among the mothers who were exposed to family members who were smokers either inside or outside the house. There was no dose–response relationship in birth weight of the babies born to mothers who were exposed to SHS, and there was no relationship with the trimester at which the mother was exposed to SHS [Table 3].
| Discussion|| |
A number of studies have been conducted across the world, mostly in developed countries to determine the association of exposure to SHS with birth weight of the newborn and the results were also inconsistent. This study is a preliminary step toward understanding the extent the problem in this part of the country.
The proportion of women exposed to SHS at home or workplace was 69.9%, which was very high when compared to studies by Goel et al. in Northwestern India and Gupta et al. in Uttar pradesh which were about 24.4% and 26.0%, respectively. Similarly, lower prevalence was reported in other parts of the world ,,, which contradicts our study findings. The higher prevalence may be attributed to the fact that the smoking is highly prevalent in public places and in workplace in this part of the country and there are no strict laws prohibiting the use of smoke products at the public places. These marked International variations regarding the prevalence rates may also be attributed to the fact that exposure to SHS was measured subjectively by self-reported exposure, and there is no validated instrument for measuring the exposure to SHS objectively, which might underestimate or overestimate the study findings. Moreover, 23.68% of the women belonged to family, where family members were smokers. This further shows the higher risk of exposure to SHS.
A review by Wickström  showed that 15%–25% of women use tobacco during their pregnancy across the globe which is contrasting to our study findings which shows that only four  had ever used tobacco in the past (3 smoke form and 1 smokeless form). However, no woman used any form of tobacco during pregnancy. This might be due to cultural difference in our country when compared to other parts of the world.
Our study findings failed to show any association between exposure to SHS during pregnancy and low birth weight of the infants. Similarly, there was no significant difference in birth weight among the mothers who were exposed to family members who were smokers either inside or outside the house. The results of previous studies were also inconsistent. A study by Gupta et al. showed that women who are exposed to SHS during pregnancy had higher chance of delivering babies of low birth weight, whereas a study by Goel et al. reported that there was no significant reduction in birth weight although there was higher chance of preterm deliveries among exposed women. Internationally, studies by Norsa'adah and Salinah et al. in Malaysia and Mojibyan et al. failed to show any association between maternal exposure to SHS and low birth weight, whereas studies by Khader et al. in Jordan and Wahabi et al. in KSA showed significant association between the two.
The strength of the present study is that it is one among the few studies conducted to determine the association of maternal exposure to SHS and low birth weight. Since the study was conducted among larger representative sample, it is upheld that the potential introduction of a selection bias was deterred. Since the study measures the self-reported exposure to SHS, the results could be underestimation or overestimation. Furthermore, estimation of the length of exposure was also difficult which was major limitations of our study.
| Conclusion and Recommendations|| |
Maternal exposure to SHS was found to be high in this part of the country with more than two-thirds of the pregnant women exposed to SHS during their pregnancy. However, there was no association with the low birth of the newborns. Since there are no strict laws prohibiting tobacco smoking in public places and at homes in our country, the SHS exposure is high as expected. With the scarcity of literature about the maternal second-hand exposure and low birth weight in our country, this study could be a preliminary step in understanding the extent of the problem. However, further studies using biomarkers are recommended to quantify SHS exposure objectively.
Financial support and sponsorship
Intramural funding for undergraduate short term research project.
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]