The Impact of E-cigarettes During Pregnancy on Childhood Health Outcomes Study

Background Much is already known about the negative health effects of tobacco smoking during pregnancy. There is no national data on smoking in pregnancy but research indicates that up to 10% of Irish women continue to smoke tobacco in pregnancy. Tobacco smoking is associated with significant obstetric and perinatal complications including preterm birth, premature rupture of membranes, placental abruption, placenta previa and intrauterine growth restriction and stillbirth. Tobacco smoking is associated with a higher incidence of congenital abnormalities. Infants born to smoking mothers are at increased risk of necrotizing enterocolitis in the neonatal period, and of sudden infant death syndrome (SIDS). Children of smokers have an increased prevalence of wheeze and asthma. There is emerging evidence of cognitive impairment with higher rates of abnormal behavioural and neurodevelopmental outcomes such as attention deficit hyperactivity disorder (ADHD) and poor academic performance in the off-spring of mothers who smoke in pregnancy.

The popularity of electronic nicotine delivery systems (ENDS) has risen significantly over the past 10 years particularly among young adults and adolescents. ENDS (also called e-cigarettes or vaping devices) are battery powered devices that heat a solution (e-liquid) to create an aerosol that contains nicotine. In addition to nicotine, the e-liquid often contains different flavourings as well as the compounds Propylene Glycol and Glycerin. The vapour created by heating e-liquid at high temperatures alters the chemical profile of the original liquid by producing hazardous compounds such as aldehydes. More than 15,000 different flavours have been reported to date. ENDS aerosols contain fewer harmful substances when compared with tobacco smoking. As a result, they have been proposed as a safer alternative to tobacco smoking. Much research on these devices currently focuses on their role as a tobacco cessation tool. Currently there is insufficient evidence to determine if ENDS are a safe and effective long-term tobacco cessation method. However, there is emerging evidence that are not harmless products and that they contain toxic compounds which have hazardous effects on different organs in the body to users.

Research on the long-term health effects of ENDS, particularly from animal studies, suggests that there are negative growth, cardiopulmonary and neurological physiological changes caused by ENDS. Animal models have demonstrated that chronic exposure to ENDS results in increased arterial stiffness, vascular endothelial changes, increased angiogenesis and atherosclerotic plaque formation. Pulmonary changes including increased airway hyperreactivity, airway obstruction, inflammation and emphysematous changes have all been documented in animal studies on ENDS. Neurotoxic effects reported in mice studies include calcium dyshomeostasis, epigentic changes, impaired autophagy and neurotransmission, oxidate stress, mitochondrial dysfunction and neuroinflammation. As nicotine, the primary ingredient in ENDS, easily crosses the placental barrier; these harmful effects have the potential to impact the unborn foetus of pregnant women who use ENDS.

There is a paucity of real world data on the fetal and neonatal effects of ENDS use during pregnancy. A few studies which have examined obstetric and birth outcomes in women using e-cigarettes during pregnancy with mixed results. An Irish study of over 400 pregnant women reported that birth weight and neonatal outcomes were similar in women who were sole users of e-cigarettes when compared with non-smokers. However, two other studies did demonstrate an association between exclusive e-cigarette use during pregnancy and low birth weight and preterm delivery. These are important predictors of adverse outcomes in the neonatal period. The proposed study will help to clarify any association between ENDS use, preterm birth and fetal growth restriction.

The SNAP trial was a randomised control trial examining the effectiveness of nicotine replacement therapy (NRT) versus placebo on smoking cessation in pregnant women who smoked. The study also examined clinical outcomes at two years of age and found that children born to women on the NRT arm of the study had no adverse outcomes at two years of age. While NRT is generally considered a much safer option for pregnant women looking to quit smoking, ENDS are not currently recommended as a smoking cessation tool in Ireland or in most countries in the world. The use of ENDS among pregnant women has risen over the past decade. The exact prevalence of ENDS use is unknown but a number of studies across the world report this figure to be between 1-15%. A more recent systematic review from the US reported a prevalence of 1.2-7%, whereas the prevalence rate was 2.8% in a survey of over 4000 pregnant women in the UK.

According to the Healthy Ireland survey 2019, the current rate of ENDS use in Ireland is 5% and a further 12% have tried them at some point. Of those smokers who have made a quit attempt, 38% used ENDS. From an Irish perspective, we have very little data on the use of ENDS during pregnancy. A recent study from the Coombe Women & Infants University Hospital identified 449 pregnant ENDS over a period of 13 months (8500 deliveries per year). We expect that a similar number of ENDS users could be recruited at the other two Dublin maternity hospitals.

Knowledge gap At present, there is insufficient evidence on the clinical impact of prenatal exposure to ENDS on children. The hypotheses reported in animal studies need to be tested in longitudinal studies in humans. Real world studies are clearly needed to examine the impact of prenatal exposure of ENDS in childhood and beyond.

Research questions What are the nutritional, pulmonary, and neuro-behavioural consequences for young children born to mothers using ENDS during pregnancy?

The specific research questions are -

• Do infants exposed to ENDS in utero have a lower birthweight compared with infants of non-smokers?
• Are children exposed to ENDS in utero at a higher risk of wheeze/asthma at two years of age compared with children of non-smokers?
• Do children exposed to ENDS in utero have impaired neurocognitive functioning at the age of two years compared with children of non-smokers?
• Are these outcomes measures different between children exposed to ENDS in utero compared with children exposed to tobacco smoke in utero

Aims and objectives The aim of the ECHO study is to examine obstetric, growth, pulmonary, and neuro-behavioural outcomes over the first two years of life in children exposed to ENDS in utero and compare them with children born to pregnant women who are either tobacco smokers or non-smokers.

The objectives of the study are -

• To establish whether infants born to mothers who are ENDS users are at a higher risk of preterm birth compared with non-smokers but lower risk compared with smokers
• To establish whether there are significant differences in growth between children of women who use tobacco or ENDS and children of non-smokers
• To establish whether parent reported and doctor confirmed wheeze and/or asthma occurs more frequently in children exposed to ENDS in utero compared with children of non-smokers and less frequently compared with children of tobacco smokers
• To establish whether there are differences in healthcare utilisation between children exposed to tobacco smoking or ENDS in utero and children of non-smokers
• To establish whether there are significant differences in neurocognitive outcomes between children of women who use ENDS, women who smoke tobacco and children of non-smokers

Inclusion criteria

• Women aged 18 or greater and less than 46 years of age at booking
• Pregnant with a singleton fetus
• Smokers (exhaled CO reading of greater than or equal to 4) or
• Self-reported vaper or
• Dual user (smoker/vaper)
• Non-smokers
• Able to understand and read English.
• Willing to agree to follow-up for the two-year duration of the study in the postnatal period (ie. unlikely to move out of the catchment area).

Exclusion criteria

• Women pregnant with twins or higher order multiples
• Late bookers - defined as booking after 24+0 weeks' gestational age
• Fetus or infant diagnosed with a major congenital abnormality (major structural abnormality, ie congenital diaphragmatic hernia (CDH), omphalocele, major cardiac defects ie. which require immediate admission to NICU +/- transfer to cardiology for surgery, chromosomal abnormalities, syndromes - Turner's/Noonan's) or a lethal fetal anomaly
• Any inherited disorder of metabolism or Cystic Fibrosis on Guthrie Card/ neonatal blood spot screening
• History of significant medical disorder in pregnancy e.g. cardiac, haematological, or endocrine disease (including gestational diabetes requiring insulin)
• Significant maternal psychiatric disorder, e.g. delusional or psychotic disorders, severe depression requiring hospitalisation, use of >1 psychotropic drugs for treatment
• Serious co-morbid addiction issues e.g. opiate abuse, methadone maintenance program
• Severe intellectual disability or lack of capacity