Norwich researchers say online adverts encouraging pregnant smokers to get support to quit could be more effective than clinical advice.

A new study - led by the University of Cambridge with the University of East Anglia (UEA) and University of Nottingham - is the first to investigate online uptake of support to help pregnant women stop smoking.

They said it could reach larger numbers of women earlier in their pregnancies, at a lower cost.

Dr Joanne Emery, from UEA's school of heatlh sciences, said: 'This study shows that online advertising appears to be a valuable means of promoting health interventions to hard-to-reach groups.

'We found that a significant minority of pregnant smokers were willing to initiate an automated text messaging intervention when offered this online. Given the high reach of the internet this could translate into substantial numbers of pregnant smokers supported to quit.'

Researchers explored the uptake of stop smoking service MiQuit - an NHS-supported text messaging scheme - and looked at strategies to increase its reach.

They advertised links to a website providing MiQuit information on Google and Facebook - as well as the National Childbirth Trust and NHS Choices websites - and recorded the number of times adverts were shown and clicked on, and characteristics of those using the service. They found at overall uptake rate of 3.4pc among people who clicked on the adverts.

More than half of online initiators texted a quit date to the system, while roughly two thirds continued using the service until the end of the 12-week programme.

Roughly half of those starting MiQuit via Google were within their first five weeks of pregnancy. Generally, the earliest interventions to help pregnant women stop smoking take place at their antenatal booking appointment, roughly eight to 12 weeks.

The research team also found that the average cost of Google and Facebook adverts was £24.73 for MiQuit initiation and an estimated £736 per confirmed quitter, cheaper than current intervention methods.

Reducing smoking prevalence in pregnancy is a key public health priority in the UK, where it is a leading preventable cause of adverse prenatal outcomes including miscarriage, stillbirth and prematurity.

It is also linked with a wide range of infant health problems. Around 11pc of UK women smoke throughout pregnancy and rates rise considerably with increasing social deprivation, exacerbating health inequalities.