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NEONATAL SOCIETY ABSTRACTS

Mode of delivery and offspring Body Mass Index, overweight and obesity in adult life: a systematic review and meta-analysis

Presented at the Neonatal Society 2012 Summer Meeting (programme).

Darmasseelane K, Hyde MJ, Gale C, Santhakumaran S, Modi N

Neonatal Medicine, Imperial College London, 369 Fulham Road, London, SW10 9NH, UK

Background: The last two decades have seen a significant rise in prevalence of obesity in England from 16.4% to 24% between 1995 and 2007, and a parallel increase in incidence of Caesarean section (CS) (1). CS has been associated with many negative long-term health outcomes, including increased offspring Body Mass Index (BMI) in childhood (2), possibly due to alterations to neonatal metabolism and gut flora. To date studies looking at the association between mode of delivery and adult BMI have been relatively small and contradictory. We conducted a systematic review and meta-analysis to evaluate the effect of mode of delivery on offspring body mass index (BMI) in adulthood. Secondary outcomes were (a) were incidence of overweight (BMI >25) and (b) incidence of obesity (BMI > 30).

Methods: A literature search was conducted in Pubmed, Google Scholar and Web of Science using pre-defined search terms, following an established protocol. For inclusion a study must have reported (a) both mode of delivery and adult BMI (b) mode of delivery with long-term offspring follow-up or (c) adult offspring BMI with birth characteristics. Reference lists were hand-searched for further potential studies. Efforts were made to contact the author to obtain further information if required. A meta-analysis of all studies with relevant data was carried out in RevMan5 using the inverse variance method. Random effects models were used throughout as the homogeneity assumption was considered untenable for unadjusted observational data. Forest plots were used to illustrate results and funnel plots were used to investigate publication bias. All data is presented as mean differences or Odds Ratios (OR) at the 95% confidence interval.

Results: 33 studies were suitable for inclusion in the review; of which 10 studies provided data in a form that could be used in a meta-analysis. Comparing the CS group with the vaginal delivery (VD) group, the meta-analysis found an unadjusted mean BMI difference of 0.45 kgm-2 [0.17, 0.74] (p < 0.002; 9 studies; 36091 subjects: CS = 2932, VD = 33169). Gender specific subgroup analyses revealed a mean BMI difference of 0.39 kgm-2 [0.06, 0.73] (p = 0.02) in males and 0.40 kgm-2 [0.12, 0.68] (p = 0.005) in females. Furthermore, when comparing CS to VD (all subjects) the pooled unadjusted OR for incidence of overweight was 1.26 [1.15, 1.37] (p < 0.00001), and the OR for incidence of obesity was 1.23 [1.06, 1.42] (p < 0.006); similar results were found in gender specific subgroup analyses. Data from 3 studies were suitable for inclusion in a subgroup analysis comparing type of CS (emergency/in-labour CS (IL-CS) and elective/pre-labour CS (PL-CS)). Populations of these groups were very small (IL-CS: n = 270, PL-CS n = 252), and subsequent metaanalyses showed no significant difference in BMI, overweight and obesity when compared to VD group.

Conclusion: This meta-analysis shows an association between CS and increased offspring BMI, overweight and obesity in adulthood. We were not able to adjust the analyses for maternal BMI, breastfeeding and socioeconomic status, key confounders that may influence offspring outcome. The results from this study call for either a randomised controlled trail of CS versus VD, or the initiation of a large-scale rigorously designed prospective observational cohort, to identify the true impact of CS on offspring health.

Corresponding author: matthew.hyde02@imperial.ac.uk

References
1. Hyde MJ, et al. (2012) Biol Rev Camb Philos Soc. 87, 229-243.
2. Utz R, et al. (1998) Policy Perspectives 4(4) (online: www.cppa.utah.edu [accessed 01/05/12])

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