BACKGROUND Stopping cigarette smoking in pregnancy positively impacts on the incidence of preterm birth, intrauterine growth restriction, and stillbirth. Electronic cigarettes (E-cigarettes) are viewed by some women as a lower risk alternative to tobacco smoking during pregnancy and are cautiously endorsed in some parts of the UK to support smoking cessation(1), however, robust, high-quality data on the impact of E-cigarettes on pregnancy and childhood health outcomes are lacking.

OBJECTIVE The objective of the ECHO study is to investigate the impact of maternal E-cigarette use during pregnancy on obstetric, neonatal, and infant outcomes.

METHODS Pregnant women attending three, large, standalone, urban, university, maternity units in Dublin, Ireland, will be invited to take part in this prospective, multicentre, observational cohort. Smoking and vaping patterns will be assessed using digital patient questionnaires. Objective assessment of breath carbon monoxide and urine cotinine levels will accurately determine exposure status at pre-specified timepoints. A third trimester ultrasound will assess growth and fetal dopplers across all groups. Postnatally, infants will undergo anthropometric measurements and developmental checks. A subgroup of 150 randomly selected infants will be assessed with the Bayley's Scales of Infant and Toddler Development.

DISCUSSION Nicotine-containing E-cigarettes are addictive and their long-term impact on pulmonary, cardiovascular, and neurological function on developing humans is undetermined. This study is ambitious as it aims to longitudinally assess the outcomes of the mother/baby dyad, examining the impact of vaping on pregnancy, neonatal and infant health, growth and neurocognitive outcomes.

TRIAL REGISTRATION ClincialTrials.gov NCT06297005.