BACKGROUND
Smoking cessation improves pregnancy outcomes, yet there is uncertainty around the efficacy of models of antenatal interventions for smoking cessation in pregnancy.

OBJECTIVE
To test the Smoking cessation Through Optimization of clinical care in Pregnancy (STOP) clinic as a novel antenatal care pathway for smoking cessation in pregnancy. The STOP intervention is a smoking cessation clinic staffed by a dedicated multidisciplinary team of obstetricians, midwives and smoking cessation practitioners, who provide motivational and psychological support and intensive clinical monitoring of pregnancy.

STUDY DESIGN
A pragmatic randomized controlled trial of the STOP clinic compared to routine antenatal care at a tertiary urban maternity hospital delivering over 8000 infants per year. The primary outcome measured was continuous abstinence from smoking prior to 28+0 weeks gestation and sustained throughout the duration of the pregnancy, validated using biological measures. The secondary outcomes included maternal and fetal morbidity; delivery and neonatal outcomes; smoking outcomes and qualitative measures.

RESULTS
Four hundred and thirty-six women were randomized with 430 women included in the primary outcome analysis. 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 4-6 months following delivery. The mean birthweight was similar in both intervention and control arms, however quitters in both groups had significantly higher birthweights than continued smokers.

CONCLUSIONS
The STOP antenatal model of care leads to higher smoking cessation rates among pregnant smokers and lower daily cigarette consumption at time of delivery. Currently there is no defined or dedicated antenatal pathway for pregnant smokers, despite the high-risk nature of their pregnancies. Our findings suggest that improved smoking cessation rates in pregnancy may be achieved using the holistic approach of the STOP model of care.