The participants will be recruited before 25 weeks gestation when they attend NHS hospital clinics for routine antenatal ultrasound scans. Recruitment will take place in around 12 United Kingdom (UK) centres over a 12 month period. Follow-up will be via telephone at 1 month after randomization and again at week 36 gestation. The follow-up is over a 9 month period. If a participant reports they have stopped smoking, this "quit" will be validated with a exhaled Carbon Monoxide (CO) measurement and/or salivary cotinine measurement.