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Mode of Delivery and Offspring Body Mass Index Z-Score in Childhood: A Systematic Review and Subject Level Meta-Analysis of International Data

Presented at the Neonatal Society 2013 Summer Meeting (programme).

Hyde MJ, Darmasseelane K, Gale C, Santhakumaran S, Modi N on behalf of the Mode of delivery and offspring BMI study group*

Section of Neonatal Medicine, Imperial College London, Chelsea and Westminster Hospital Campus, 369 Fulham Road, London, SW10 9NH, UK

Background: We have previously suggested that mode of delivery is a plausible determinant of life-long health, with exposure to normal labour and/or vaginal microbial initiating key metabolic and immune trajectories (1). Here we present preliminary results of a systematic review and meta-analysis of subject-level data to test the hypothesis that there is a statistically significant and clinically relevant difference in offspring Body Mass Index (BMI) z-score in childhood in relation to mode of delivery.

Methods: A literature search was conducted in Pubmed using pre-defined search terms, following a registered protocol. Inclusion required that the study reported (a) mode of delivery and childhood BMI (b) mode of delivery with long-term offspring follow-up or (c) offspring BMI in childhood with birth characteristics. Reference lists were hand-searched for further potential studies. Authors were contacted to obtain subject level data on outcomes of interest. BMI z-score was calculated using the International Obesity Task Force criteria. A meta-analysis was carried out in RevMan5 using the inverse variance method and random effects models. Subgroup analyses were used to explore differences between Vaginal Delivery (VD) and either emergency/in-labour Caesarean Section (IL-CS) and elective/pre-labour CS (PL-CS). Results are presented as mean difference [95% confidence interval].

Results: Data were obtained from 21 international studies (631,427 subjects; of which 96,740 were CS deliveries). The mean difference in BMI z-score between CS and VD groups was 0.12 [0.09, 0.16] (p<0.0001). Data from 8 studies (167,847 subjects) were suitable for inclusion in the subgroup analysis; mean difference in BMI z-score comparing IL-CS with VD 0.07 [0.04, 0.10] (p<0.0001); 0.03 [-0.01, 0.07] comparing PL-CS and VD.

Conclusion: Using individual data from over half a million children we identify an association between CS and increased offspring BMI z-score in childhood. This is in keeping with our previous report of a significant difference in BMI between adults born by CS or VD (2). The implication of a possible difference between type of CS is uncertain and it is important to note that the association between mode of delivery and offspring outcome is liable to confounding. We aim to explore these aspects, including adjusting for potential confounders to further address the possibility that mode of delivery affects life-long health.

Corresponding author:

1. Hyde MJ, et al (2012) Biological Reviews 87:229-243
2. Darmasseelane K, et al (2012), Summer Meeting of the Neonatal Society

*Members of the Mode of delivery and offspring BMI study group include: Ajslev TA, Barros F, Bhattacharya S, Castro-Rodriguez J, Cohn BA, Crume T, Eriksson J, Friedlander Y, Gissler M, Harlap S, Hartikainen JA-L, Huh S, Inskip H, Jarvelin M-R, Li H, Liu J, Nohr EA, Osmond C, Pouta A, Smith KR, Sorensen TIA, Svensson J, Teyhan A, Wijga A, Yajnik C, Zhou Y.

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