Effects of smoking cessation with voucher-based contingency management on birth outcomes

Abstract

Aims: This study examined whether smoking cessation using voucher-based contingency management (CM) improves birth outcomes.

Design: Data were combined from three controlled trials.

Setting: Each of the trials was conducted in the same research clinic devoted to smoking and pregnancy.

Participants: Participants (n=166) were pregnant women who participated in trials examining the efficacy of voucher-based CM for smoking cessation. Women were assigned to either a contingent condition, wherein they earned vouchers exchangeable for retail items by abstaining from smoking, or to a non-contingent condition where they received vouchers independent of smoking status.

Measurement: Birth outcomes were determined by review of hospital delivery records.

Findings: Antepartum abstinence was greater in the contingent than non-contingent condition, with late-pregnancy abstinence being 34.1% versus 7.4% (P<0.001). Mean birth weight of infants born to mothers treated in the contingent condition was greater than infants born to mothers treated in the non-contingent condition (3295.6 ± 63.8 g versus 3093.6 ± 67.0 g, P = 0.03) and the percentage of low birth weight (<2500 g) deliveries was less (5.9% versus 18.5%, P = 0.02). No significant treatment effects were observed across three other outcomes investigated, although each was in the direction of improved outcomes in the contingent versus the non-contingent condition: mean gestational age (39.1 ± 0.2 weeks versus 38.5 ± 0.3 weeks, P = 0.06), percentage of preterm deliveries (5.9 versus 13.6, P = 0.09), and percentage of admissions to the neonatal intensive care unit (4.7% versus 13.8%, P = 0.06).

Conclusions: These results provide evidence that smoking-cessation treatment with voucher-based CM may improve important birth outcomes.

Figure 1

Upper panel shows 7-day point-prevalence smoking abstinence in the contingent (open bar) and noncontingent (closed bar) treatment conditions at end-of-pregnancy assessment (upper panel). Treatment conditions differed significantly (P = .001). Bottom panel shows mean percent of all antepartum smoking-status tests that were negative for recent smoking in each treatment condition. Brackets represent 1 ± SEM. Treatment conditions differed significantly (P < .0001).

Figure 2

Birth weights of infants born to mothers treated in the contingent (left column) and noncontingent (right column) treatment conditions. Each symbol represents an individual infant’s birth weight and the solid line in each column represents the least square mean weight for that condition. The dashed line demarcates the 2500 g cutoff for low birth weight. Mean birth weight differed significantly between treatment conditions (P = .03) as did the percent of low birth weight deliveries (P = .02).