Preconception lifestyle interventions for women-a systematic review and meta-analysis of intervention characteristics and behaviour change techniques.

Background: The time before conception is an important opportunity to improve maternal lifestyle, and hence improve fertility and health. However, the components of effective preconception lifestyle interventions are unclear.

Objective And Rationale: This review aimed to assess the association of intervention characteristics and behaviour change techniques with the effect of lifestyle interventions on fertility, obstetric, foetal, anthropometric, and metabolic outcomes in women planning a pregnancy. Understanding the optimal components of preconception lifestyle interventions is essential to improve success of future interventions.

Search Methods: We searched Ovid MEDLINE, PsycINFO, Embase, Emcare, Scopus, Cochrane Central Register of Controlled Trials, and CINAHL (6 December 2024). We included randomized controlled trials on women planning a pregnancy which assessed the effect of lifestyle intervention compared to standard minimal care or no intervention on fertility, obstetric, foetal, anthropometric, and metabolic outcomes. We performed random-effects meta-analysis with subgroup analysis based on participant characteristics, intervention characteristics (using the Template for Intervention Description and Replication (TIDieR) framework), and behaviour change techniques (using the Behaviour Change Taxonomy v1). We assessed trustworthiness (using the Trustworthiness in Randomised Controlled Trials (TRACT) checklist), risk of bias (using the Cochrane Risk of Bias 2.0 tool), and certainty of the evidence (using the GRADE approach).

Outcomes: Following eligibility screening and trustworthiness assessments, we included 24 studies (n = 7795 women), of which the majority were conducted in high-income countries (79%) and studied women with infertility (67%). Risk of bias was low for seven studies, some concerns for 15 studies and high for two studies. Overall, there was no difference in clinical pregnancy (odds ratio [95% CI]: 1.06 [0.84, 1.35], I2 = 24.22%) or live birth (odds ratio [95% CI]: 1.17 [0.82, 1.67], I2 = 48.73%) with lifestyle intervention. Odds of clinical pregnancy were higher for interventions delivered over ≥10 sessions (2.17 [1.21, 3.86] vs 0.88 [0.72, 1.07], P = 0.004 for subgroup differences) and with the behaviour change technique Adding objects to the environment (e.g. provision of intervention-compliant food and/or exercise equipment) (3.51 [1.70, 7.23] vs 0.90 [0.75, 1.08], P < 0.001 for subgroup differences). Lifestyle interventions reduced weight (mean difference [95% CI]: -3.87 kg [-5.76, -1.97], I2 = 95.03%) and fasting blood glucose (mean difference [95% CI]: -0.15 mM [-0.25, -0.04], I2 = 0%). Greater weight loss was observed for interventions with a weight loss aim (-4.19 kg [-6.30, -1.92] vs -0.81 kg [-1.48, -0.14], P = 0.003 for subgroup differences). Greater weight loss was observed for interventions delivered solely via face-to-face (-6.02 kg [-8.96, -3.07]) compared to those delivered via a combination of face-to-face and technology (-2.21 kg [-3.62, -0.81], P = 0.02 for subgroup differences).

Wider Implications: Effectiveness of preconception lifestyle interventions aiming to enhance fertility may be improved by a structured, intensive approach. Preconception lifestyle interventions reduce weight, particularly face-to-face interventions with a weight loss aim. However, these findings based on subgroup analyses should be interpreted with caution and warrant further investigation due to the exploratory nature of the analysis, limited number of studies included, and potential aggregation bias of study-level subgroup effects. Selection of intervention characteristics for future preconception lifestyle interventions should consider patient preferences and practical considerations.

Registration: This review was prospectively registered in the Prospective Register of Systematic Reviews (PROSPERO) (CRD42022333066).