Smoking Cessation Through Optimisation of Clinical Care in Pregnancy: The STOP Randomised Controlled Trial

Maternal smoking in pregnancy is a leading cause of maternal and fetal morbidity and mortality. Smoking rates are declining in the western world; however, this decline is uneven, modulated by social class and deprivation. Despite being an important reversible risk factor, there is a lack of focus on smoking cessation within obstetrics.

Our early work identified smokers as a group that engaged with healthcare less readily than their non-smoking counterparts, despite their significantly heightened clinical risk. This group of pregnant smokers were younger (29yrs vs 33yrs p<0.001) and of higher parity (1.4 vs. 1.0 p<0.001) than non-smokers. They were less likely to have a planned pregnancy (44.4% vs 79.6%, p<0.001) and less likely to have taken pre-conceptual folic acid (22.2% vs 58.3%, p<0.001). They also had a higher rate of history of illicit drug use, particularly cannabis (19.1% vs 0.9%, p<0.001) and opiates (16.1% vs 0.9%, p<0.001). Mental health issues were commoner in smokers with 36.3% describing depression, postnatal depression or bipolar disorder and 34.3% experiencing anxiety disorder or panic attacks. Our institution was provided little support to smokers, with only 36.5% of women documented to have received smoking cessation advice. No smokers were referred for smoking cessation interventions. In terms of additional clinical needs, two thirds of smokers were referred back to the Obstetric team from Midwifery Led Care for management. This was primarily due to either concerns over fetal size, or recurrent non-attendance at antenatal clinics. Two thirds of smokers were referred for an additional ultrasound, largely due to suspected fetal growth restriction.

With these issues in mind, we designed a holistic, comprehensive clinic that would deliver care to these women in pregnancy, called the STOP clinic. This clinic provided a smoking cessation intervention in tandem with obstetric-led care. We tested this by a pragmatic randomised controlled trial. Women attending the STOP antenatal clinic were more likely to quit smoking than those in routine care (Odds Ratio 3.62 (95%CI 1.43 to 9.17). Additionally, women who continued to smoke in the STOP clinic smoked fewer cigarettes daily at the time of delivery than controls: 5 ± 4 in STOP clinic participants and 7 ± 5 in control group, OR 0.28 (0.13 to 0.59). However, this intervention did not alter postpartum relapse rates, (4.3% intervention arm vs 1.5% control arm, not significant) at 4-6months following delivery. Pregnant smokers, as a cohort, have a relatively high rate of poor obstetric outcomes and often encounter barriers to accessing healthcare. The STOP clinic therefore offers a novel antenatal solution to their care.

This thesis also presents work on other topics related to smoking in pregnancy. Electronic cigarettes (EC) are a relatively new phenomenon, but one with an increasing prevalence of use among expectant mothers. We published obstetric outcomes of electronic cigarette users in one of the first publications of its type internationally. Infants born to EC users had a mean birth weight of 3470g (+/-555g), which was similar to that of non-smokers (3471g +/-504g, p=0.97) and significantly greater than smokers (3166g +/-502g,p<0.001). As an observational study only, further research is needed on the impact of EC use on clinical outcomes in pregnancy.

We analysed the use of illicit tobacco in pregnant smokers who face a significant financial burden from smoking. The use of illicit tobacco was low among pregnant smokers and only a minority of women engaged in tobacco tax avoidance. As the average price of tobacco in Ireland increases, weekly expenditure on tobacco products is a significant financial impact on low-income women. Smoking cessation would therefore deliver significant financial gains in addition to health benefits.