RESEARCH PAPER
Residential Environmental Tobacco Smoke Exposure During Pregnancy and Low Birth Weight of Neonates: Case Control Study in a Public Hospital in Lucknow, India
DIVYA KHATTAR, SHALLY AWASTHI, AND *VINITA DAS
From the Departments of Pediatrics, and * Obstetrics and Gynecology, CSMMU, Lucknow, Uttar Pradesh, India.
Correspondence to: Prof. Shally Awasthi, Department of Pediatrics, CSMMU (Erstwhile King George’s Medical College), Lucknow, Uttar Pradesh, India.
[email protected]
Received: December 7, 2011; Initial review: December 26, 2011; Accepted: March 30, 2012.
PII: S097475591100998-1
INDIAN PEDIATRICS
JUNE 10, 2012 [E-PUB AHEAD OF PRINT]
KHATTAR, et al.
ENVIRONMENTAL TOBACCO SMOKE AND LBW
ABSTRACT Objective: To determine whether residential environmental tobacco smoke (ETS) exposure during pregnancy is associated with low birth weight (LBW) neonates and establish a dose response relationship. Methodology: Case control study carried out in a tertiary care hospital in Lucknow, India from May to July 2011. Excluded were women smokers and tobacco chewers, high parity (>3), multiple pregnancy and still births. Included were 100 cases and 200 controls, aged 20 to 30 years. Mothers giving birth to LBW neonate (20 cigarettes smoked/day, OR = 17.62, 95% CI= 3.76-82.43). Conclusion: Exposure to ETS during pregnancy is associated with LBW of neonates. Hence, there is an urgent need to increase awareness about health hazards of ETS during pregnancy and bring about behavioural changes accordingly as a one of the strategies to reduce LBW deliveries in India. Key words: Environmental tobacco smoke, Etiology, India, Low birth weight, Neonate, Passive smoking.
Low Birth Weight (LBW) is a major public health issue in developing countries like India, where its prevalence is as high as 30% [1]. This may be the outcome of either preterm birth or retarded intrauterine growth. LBW leads to an impaired growth of the infant resulting in a higher mortality rate, increased morbidity, predisposition for infectious diseases, lowered cognitive abilities and chronic adult diseases [2, 3]. Etiology of LBW is multi factorial and is related to maternal, fetal, placental and environmental risk factors including Antenatal care (ANC) status and socio economic status of the mother [4]. Maternal smoking is an established cause of LBW [5]. Passive smoking containing the same toxic substances can be expected to have a similar effect on the fetus. INDIAN PEDIATRICS
JUNE 10, 2012 [E-PUB AHEAD OF PRINT]
KHATTAR, et al.
ENVIRONMENTAL TOBACCO SMOKE AND LBW
In India, although women smokers are scarce, they are exposed to the ill effects of tobacco smoke due to passive smoking at their home during their pregnancy [6]. Tobacco use in the form of smoking among males in India is around 33.3% [7] and environmental conditions like overcrowding and poor ventilation at home make the health effects of environmental tobacco smoke (ETS) more pronounced in such settings. Residential ETS exposure in India was reported to be 52.5% [8]. Studies investigating the association between maternal ETS exposure during pregnancy and birth outcomes had reported varied findings in developed countries [9, 10]. Such studies are lacking in developing and under developed countries [11]. Considering that residential ETS exposure during pregnancy is an easily preventable factor, the current study was undertaken to examine its association with LBW babies born in a tertiary care hospital in Lucknow, northern India and hence quantify the degree of association. A dose response relationship was also studied to assess the severity of ETS exposure. METHODS This was a hospital based case control study conducted from May 2011 to July 2011 at Queen Mary Hospital, attached to Department of Obstetrics and Gynecology, CSMMU, Lucknow, a tertiary care government hospital in Northern India. Approval was obtained by the Institutional Ethics Committee (IEC). Before enrollment, written informed consent was obtained from all the participants. Cases were mothers, in the age group 20 to 30 years, who had delivered a singleton live neonate with birth weight < 2.5 kg (LBW). Controls were mothers in the age group 20 to 30 years, who had delivered a singleton live neonate with birth weight ≥ 2.5 kg. As teen (30 year) pregnancies are at an increased risk for LBW babies [12], mothers of age group 20 to 30 years have been included in the study. Only mothers delivering singleton neonates have been enrolled as multiple pregnancy is also associated with higher risk for LBW. Excluded from cases and controls were (a) women smokers and tobacco chewers (as they are at an increased risk for delivering LBW neonate); (b) high parity(>3) as such pregnancies have been associated with a decrease in birth weight of the neonate [13]; (c) birthweight not documented; and (d) still births. The sample size was calculated using Open Epi statistical tool. According to Global Adult Tobacco Survey, Fact Sheet India: 2009-2010, residential ETS exposure was found to be 51.3%. So, to assess odd’s ratio of 2.25 for LBW babies with an alpha (α) of 0.05 and power of 0.8, the total sample size calculated is 257. This study was conducted with a sample size of 300. INDIAN PEDIATRICS
JUNE 10, 2012 [E-PUB AHEAD OF PRINT]
KHATTAR, et al.
ENVIRONMENTAL TOBACCO SMOKE AND LBW
During the study period, the birth register maintained at QMH was reviewed every day. For every case (LBW) selected, two consecutive controls (birth weight ≥ 2.5 kg) were enrolled. This ratio of 1:2 for case: control resulted in participation of 100 cases and 200 controls. Higher number of controls were taken to maximize the statistical power of detection. Data collection tool: Data were abstracted from hospital records for maternal hemoglobin levels, birth weight and gestational age of neonate. Preterm birth was defined as gestation age
