Abstract

Objective: to study the association between exposure to Environmental Tobacco Smoke (ETS)  during pregnancy and the adverse birth outcomes in Egypt. Materials and Methods: Target population were mothers admitted in the postnatal ward of the obstetrics department of an educational hospital, giving birth to viable single neonates with or without adverse birth outcomes. The total sample size was 345, and a pre-designed pre-coded structured interviewing questionnaire in Arabic language was used to collect data from the study population within 24 hours after delivery. Results: The study revealed that mothers who reported regular exposure to ETS had two times more risk to experience adverse birth outcomes than mothers who reported no exposure (OR=2.0, 95% CI= 1.13-3.58).  Mothers who were regularly exposed to ETS during pregnancy had 1.36 times more risk to have preterm babies, two times more risk to have small for gestational age (SGA) babies and 3 times more likely to have low birth weight (LBW) babies than mothers who were not exposed to ETS (OR=1.36, 95% CI= 0.59-3.09), (OR=1.97, 95% CI= 0.73-5.3) and (OR=2.74, 95% CI= 1.38-5.46) respectively. There was no significant association between exposure to ETS during pregnancy and the risk of congenital anomalies or Neonatal Intensive Care Unit (NICU) admission. Conclusion: Mothers regularly exposed to ETS had two times more risk for adverse birth outcomes compared to non-exposed. Birth weight was the only birth outcome significantly associated with gestational exposure to ETS and low birth weight was the adverse birth outcome most affected by ETS exposure.

Introduction

"Adverse birth outcome" implies diagnosis of at least one or more of the following conditions in current pregnancies: newborns with preterm birth (PTB (, postdate, low birth weight (LBW), macrosomia, small for gestational age (SGA), large for gestational age (LGA), birth defects and abortion or stillbirth [1]. Adverse birth outcomes are significant public health issues and common health problems in developing countries having negative consequences on infants’ health with emotional and economic costs on families and communities [2]. The economic cost of adverse birth outcomes includes medical care (immediate and long term), early intervention, and loss of productivity in disabling conditions. This economic cost was estimated to be more than 26 billion dollars annually [3].

Environmental Tobacco Smoke (ETS) exposure is defined as being in the presence of passive smoke at least 15 minutes per day on more than one day per week [4]. Regular exposure to ETS is defined as being exposed most days and/or nights to ETS [5]. ETS includes materials in the air originating from burned or heated tobacco. Exposure continues after smoking stops and includes second and third-hand smoke [6]. Globally, 40% of children, 35% of female non-smokers, and 33% of male non-smokers are exposed to ETS. ETS contributes to 1% of worldwide mortality, with the majority of the deaths in women (47%) and children (28%) [6]. Being female is a major risk factor for ETS exposure [7]. According to the US department of health and human services, 37% of pregnant women are exposed to ETS [8]. In China, less than 2% of women smoke, but approximately 44% are exposed to ETS for at least 15 min per day on at least one day per week [9].  In Egypt, it is estimated that approximately 75% of females are exposed to passive smoking at their homes [10]. The prevalence of (ETS) exposure during pregnancy seems to be high. The Department of Health Services (DHS) data analysis reported that ETS exposure in pregnancy was 82.9% in south-east Asia, 17.1% in the Democratic Republic of the Congo and 91.6% in Pakistan [11].

Exposure to tobacco smoke affects all stages of human reproduction. Maternal cigarette smoking is associated with increased risks for ectopic pregnancy, premature rupture of membranes, abruption placentae, placenta previa, miscarriage, stillbirth, PTB, LBW, SGA, and congenital anomalies such as cleft lip and palate [12].  Smoke exposure during pregnancy also has adverse effects on neurological health and behavior of infants and children [13,14].

The negative impact of tobacco smoking on birth outcomes is not limited to its direct use by the mother. Maternal exposure to ETS in pregnancy has also been associated with reduction in birth weight, length, and head circumference in Taiwan [15]. ETS exposure during pregnancy was also associated with higher risk of miscarriage and still birth [16]. Some studies reported association between gestational exposure to ETS and birth defects [17,18].

According to a study in England, the introduction of the smoke-free legislation particularly for pregnant women in the third trimester had positive effects on birth outcomes [19,20].

Egypt has one of the highest rates of tobacco use in the Eastern Mediterranean region. Nearly half of Egyptian men currently smoke cigarettes or other tobacco products – most of them smoke daily – compared with 0.2% of women. Data obtained from the Global Adult Tobacco Survey (GATS) conducted during 2008–2010 on individuals 15 years of age or older indicated that 53% of women in Egypt are exposed to ETS at work [21-24].

As the data about exposure to ETS during pregnancy in Egypt is deficient, the present research was carried out to determine the prevalence of environmental tobacco smoke exposure among pregnant women aiming at assessing the association between environmental tobacco smoke exposure during pregnancy and adverse birth outcomes. The current study followed the National Strategy of Science, Technology and Innovation (STI-EGY 2030), more particularly the theme of “Health and Population”.

Materials and Methods

This is a Cross-sectional study that was conducted in Damanhur National Medical Institute (DNMI) in Damanhur, El Beheira Governorate, Egypt. The researcher got the approval of Ethics Committee of the High Institute of Public Health for conducting this study and complied with the international research ethics guidelines. A written consent was obtained from the participants after explanation of the purpose of the study.

Based on a previous study [25], the prevalence of ETS exposure among pregnant women was 31.7%. Using margin of error 5% and alpha error of 0.05 the minimum required sample size was 340 pregnant women. Target population were mothers admitted in the postnatal ward of the obstetrics department at DNMI, giving birth to a viable single neonate with or without adverse birth outcomes (e.g., preterm birth, low birth weight, or congenital anomaly).

Exclusion criteria were; smoking mothers, parents with history of consanguinity, mothers with chronic medical conditions before and during pregnancy (such as hypertension, diabetes mellitus, heart disease and renal disease) and or family history of genetic diseases.

Data collection was carried out through interviewing questionnaire, clinical examination of all participants and record reviewing.

I- Interviewing technique

A pre-designed pre-coded structured interviewing questionnaire in Arabic language was used to collect data from the study population. The questions were taken and modified from similar previous researches [26-28].

The questionnaire included seven parts:

Part 1: Personal and Socio-demographic data

Part 2: Data about maternal health, obstetric history and current pregnancy

Part 3: Data on maternal occupation and occupational exposures

Part 4: Data on maternal exposure to some indoor and outdoor environmental risk factors

Part 5: Data about exposure to environmental tobacco smoke: ETS exposure is defined as being in the presence of passive smoke at least 15 minutes per day on more than one day per week [4].   Regular exposure to ETS is defined as being exposed most days and/or nights to ETS [5].

All participants were asked about exposure to environmental tobacco smoke (ETS) at home, in the workplace, in transportation, and in many public places (governmental institutes, hospitals or clinics, pharmacies, banks, cinemas, malls, restaurants, cafés, markets, bus or train stations, others). Specific questions included: number of persons smoking cigarettes (or other tobacco products), number of cigarettes (or other products) smoked per day, frequency and duration of exposure to ETS, presence of tobacco odor, size and ventilation at the designated place, exposure to ETS from nearby cafés, etc.

II- Clinical examination of mother and newborn

A pre-designed and pre-coded structured sheet was used to collect the data

III- Data collected from records:

 

Results

Our results reveal that mothers who reported regular exposure to ETS had two times more risk to experience adverse birth outcomes than mothers who reported no exposure (95% CI= 1.13-3.58).

Home exposure to ETS was significantly associated with adverse birth outcomes (X2 =5.13, P= 0.02). Mothers who were exposed to ETS at home had 1.92 times risk to have baby with adverse birth outcomes than those who weren`t exposed at home (95% CI= 1.09-3.38).

Results showed that the source of ETS at home was either cigarettes, shisha or both. Mothers exposed to both cigarettes and shisha had the highest risk to have adverse birth outcomes (OR=2.57, 95% CI= 1.08-6.07), followed by those who were exposed to cigarettes alone (OR=1.89, 95% CI= 1.06-3.41) and the lowest risk was for mothers who reported exposure to shisha alone but this risk was not significant (OR=1.32, 95%)

There was no significant difference between exposure in window ventilated rooms and non-ventilated rooms regarding the risk of adverse outcomes (OR=0.47, 95% CI= 0.13-1.67).

Our data reveal that there was a dose dependent effect; with increase in the number of people smoking cigarettes at home, the risk for having adverse birth outcomes increased with statistically significant trend value (X2= 8.18, P=0.004). With the highest risk for mothers who reported exposure to cigarette smoke from 3 or more smokers at home (OR=5.92, 95% CI= 1.52-23.1). A dose dependent effect was also observed between the number of cigarettes smoked per day and the risk of adverse birth outcomes (X2 for trend for OR =9.54, P=0.002) and the highest risk was for mothers who were exposed to ETS from 15 or more cigarettes per day (OR=2.77, 95% CI= 1.36-5.65).

Mothers who were exposed to ETS from shisha at home had 1.26 times more risk to have adverse birth outcomes than those not exposed (95% CI= 0.68-2.31). There was no significant association between the reported number of shisha stones burnt per day at home and the risk of developing adverse birth outcomes in the newborn (X2 for trend =1.83, P=0.18).

Exposure to ETS in the workplace was not significantly associated with the development of adverse birth outcomes (OR=1.2, 95% CI=0.15-9.77) and this can be explained by the small number of working mothers in the sample (only 19 mothers were employed during this pregnancy) and only five of those nineteen mothers reported exposure to ETS at work.

Regarding the frequency of exposure to ETS in transportation means (in hours), mothers who reported exposure for more than 20 hours in the whole current pregnancy had 5.35 times more risk for having adverse birth outcomes than mothers who reported exposure for less than 20 hours in the current pregnancy (95% CI= 1.19-24.03).

In spite of this significant association, the relation between exposure to ETS in transportation means in terms of (yes/no) and the risk of development of adverse birth outcomes was not significant (X2=0.55, P=0.46) and this can be explained by the observation that the previous significant frequency (>20 hours/ pregnancy) was reported in only 8 women (about 7 % of the total exposed in transportation means) and the main bulk of exposed women were in the category of (<20 hours/ pregnancy) which is the least significant frequency.

Exposure to ETS in public places was significantly associated with adverse birth outcomes (X2=4.93, P=0.02). Mothers who reported exposure to ETS in public places had 2.15 times more risk to have adverse birth outcomes than mothers who reported no exposure (95% CI= 1.08-4.27).

There was a dose dependent effect between the number of sources from which mothers exposed to ETS (home, workplace, transportation means, or public places) and the risk for adverse birth outcomes (X2 for trend for OR =3.99, P=0.04).

As regards the individual adverse birth outcomes, data revealed that mothers who were regularly exposed to ETS during pregnancy had 1.36 times more risk to have preterm babies than mothers who were not exposed to ETS (95% CI= 0.59-3.09). The risk was highest in the (34-<36 weeks) group (OR=1.88, 95%CI:0.4-1.78).

Regarding weight for age, mothers regularly exposed to ETS during pregnancy had 1.97 times more risk to have SGA babies than non-exposed mothers (95% CI= 0.73-5.3). The risk was higher for full term SGA babies than preterm SGA babies (OR=2.18, 95% CI= 0.73-6.49) and (OR=1.13, 95% CI= 0.12-11.1) respectively.

low birth weight was significantly associated with exposure to ETS during pregnancy (t =3.23, P=0.001). Mothers regularly exposed to ETS during pregnancy were about 3 times more likely to have LBW babies than those not exposed to ETS (OR=2.74, 95% CI= 1.38-5.46).

there was no significant difference between newborns of ETS exposed and non-exposed mothers regarding birth length and head circumference. It reveals that there was no significant association between exposure to ETS during pregnancy and the risk of congenital anomalies or neonatal NICU admission (X2=0.069, p=1 ) and (X2=0.116, p=0.75) respectively. The small number of congenital anomaly cases or NICU admitted cases in this study can explain this low risk.

the final multiple logistic regression model in which four factors had significant risk of having a newborn with adverse birth outcomes (regular ETS exposure, income, pregnancy related medical problems and standing for long time). The dependent factor is adverse birth outcomes. The independent factors are regular ETS exposure, income, pregnancy related medical problems and standing for long time during current pregnancy.

Mothers who reported standing for long time during pregnancy had the highest risk with Adjusted Odds Ratio (AOR) of 7.56 (95% CI=1.29-43.99), followed by mothers with pregnancy related medical problems like threatened abortion, accidental hemorrhage or poor weight gain with AOR of 3.36 (95% CI=1.76-6.43) and then regular ETS exposure during pregnancy with AOR of 2.43 (95% CI=1.31-4.51) and the least risk was for mothers who reported having just enough income (AOR=2.07, 95% CI= 1.26-3.39).

Discussion

The theory of fetal origins of adult diseases states that some intrauterine exposures can affect the programming of fetal cells and this is presented by health consequences either at birth or later in life. Environmental tobacco smoke has been proved to be one of these exposures that can influence the fetal development and also the post-natal life. In Egypt, half of women and half of children are exposed regularly to environmental tobacco smoke from a household member within the dwelling and 53% of women in Egypt exposed to ETS at work. The present study aimed at studying the association between exposure to ETS during pregnancy and adverse birth outcomes in Damanhur, El Behera governorate. In order to fulfill this aim, this cross-sectional study was conducted in an educational hospital in Damanhur, El Behera Governorate.

Regarding maternal exposure to environmental tobacco smoke during pregnancy, the majority of the study sample (81%) reported exposure to ETS either at home, in the workplace, in transportation means or in public places. Regular exposure was reported in home and workplace exposed mothers constituting about 73% of the total sample. Mothers who reported regular exposure to ETS had two times more risk to experience adverse birth outcomes than mothers who reported no exposure (95% CI= 1.13-3.58).

These results are consistent with a retrospective cohort study in 2011 in which ETS exposed women during pregnancy had higher risk of adverse birth outcomes than non-exposed women [29].  A more confirming result was shown in an American study in which ETS exposed mothers during pregnancy had the same risk of having adverse birth outcomes as active smoking mothers; both were nearly 2.5 times more likely to have preterm birth babies compared to non-smoking women. Birth weight and birth length were reduced in ETS exposed women by 306 grams and 1.4 cm respectively compared to non-exposed women [30].

In a study in Jordan, mothers who reported higher average number of ETS exposure hours per week from occupational exposure, home, or outside were at significantly greater risk for having a LBW neonate than women who reported lower average number of ETS exposure hours [31].

Many studies concentrated on the effect of household exposure to ETS on the risk of adverse birth outcomes; a study in Africa revealed that exposure to ETS at home during pregnancy was associated with increased LBW risk mainly in male newborns. There was a positive trend regarding the level of exposure as mothers exposed daily to ETS had more risk for having LBW infants than those exposed weekly [32]. In a recent study in India, household ETS exposure during pregnancy was associated with higher risk of LBW in newborns compared to no ETS exposure (OR=3.78, 95% CI: 2.39-5.98) [33]. In a retrospective cohort study, self-reported exposure to ETS at home was associated with earlier delivery (-0.19 weeks; 95% CI: -0.32 to -0.05) and reduced birth weight (-56 g, 95% CI: -97 to -16 g) [34].

A study in Indonesia reported that the association between gestational ETS exposure from a spouse and adverse birth outcomes was only significant in the group of fathers who smoked more than 20 cigarettes per day. They had higher risk of LBW infants (OR = 2.09, 95% CI: 1.38-3.17) with a 151 g decrease in birth weight and a higher risk of preterm birth (OR = 2.11, 95% CI: 1.38- 3.23) than non-smoking parents [35].

On the other hand, two studies reported no significant association between maternal ETS exposure at home or at work and any adverse birth outcomes [36,37], returning to the methodology of these two studies they differed from the current study in the timing of data collection; in the first one the questionnaire collecting the data about ETS exposure during pregnancy was administered any time between the 5th to the 39th weeks of gestation and in the second study they collected the maternal data in the 1st antenatal visit (usually within the 1st trimester) which does not indicate subsequent exposures during the rest of the pregnancy.

Being consistent with the current results, Qiu et al. 2014 [38], reported that ETS exposure during pregnancy was slightly and insignificantly associated with an increased risk of overall preterm birth (OR = 1.12, 95% CI: 0.95-1.32). Maternal exposure to ETS during pregnancy was associated with higher risk of preterm birth in some previous studies [39,40]. However, other studies found no effect of gestational ETS exposure on the gestational age or the risk of preterm birth [41, 42].

The risk of SGA was significantly higher in the ETS exposed cohorts in many previous studies [40, 41, 43]. However, according to Hoyt et al. 2018 [44], the risk of SGA babies was not statistically significant among ETS exposed women (OR=0.63 (CI: 0.27–1.46).

Our results were also consistent with many previous studies in which birth weight was the most affected birth outcome by ETS exposure during pregnancy and low birth weight was the most frequent adverse birth outcome in the ETS exposed group [45-47].

In a Korean study, there was a dose response relationship between environmental tobacco smoke exposure during pregnancy and the risk of decreased neonatal birth weight [48]. Self-reported exposure to ETS in pregnancy was associated with 35 g decrease in birth weight in newborns [25].

Contrary to our results, a cross-sectional study on 263 pregnant women based on serum cotinine levels, 50 of them were exposed to ETS during pregnancy also revealed that there was no significant association between ETS exposure and birth weight [49].The serum cotinine concentration in those fifty women ranged from 0.2 to 14.9 ng/mL and only four of them had concentration above 1.0 ng/mL. There is no approved precise cotinine cutoff value in the literature to distinguish non-smokers, ETS exposed, and active smokers. However, some studies suggest that < 3.0 ng/mL indicates low exposure to ETS and >12 ng/mL indicates high exposure to ETS [50].  From these data we can conclude that the majority of those 50 ETS exposed women in the study were exposed to very limited levels of ETS which can explain the limited effect on birth weight.

Gestational exposure to ETS was significantly associated with smaller head circumference and shorter neonatal length in some previous studies [29,41,51]. In a study on 147 neonates, the newborns of ETS exposed mothers had lower anthropometric indices, but the differences were not statistically significant [52]. An odd result was documented in a meta-analysis in which neonates of ETS exposed pregnant women were longer at birth by 1.75 cm (95% CI:1.37–2.12 cm) in 9 studies. However, the authors explained this unusual increased length to be incidental [42].

Conclusion 

Regarding maternal exposure to environmental tobacco smoke during pregnancy, the majority of the study sample (81%) reported exposure to ETS either at home, in the workplace, in transportation means, or in public places. Mothers regularly exposed to ETS had two times more risk for adverse birth outcomes compared to non-exposed. Birth weight was the only birth outcome significantly associated with gestational exposure to ETS and low birth weight was the adverse birth outcome most affected by ETS exposure. It was also associated with high risk of preterm birth and small for gestational age, but these risks were not significant.

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