Using Meta-Analysis to Answer Questions That Could Never Be Answered in a Single Trial

An example based on surgical technique for excision of cervical pre-cancer

It is well known that cervical pre-cancer is associated with increased risk of pre-term birth (with all that this entails), and that cervical treatment adds to the risk. A recent extensive meta-analysis of 70 observational studies with a control group of some sort showed that the more radical the procedure (in terms of tissue destroyed or removed), the greater the risk.[1] This is important information for women who must balance the putative benefit of deeper margins against the documented risks to a subsequent pregnancy. Where possible (i.e. milder grade lesions) it may be advisable to delay treatment until after bearing children and, indeed, not to delay having children.

— Richard Lilford, CLAHRC WM Director


  1. Kyrgiou M, et al. Adverse obstetric outcomes after local treatment for cervical preinvasive and early invasive disease according to cone depth: systematic review and meta-analysis. BMJ. 2016; 354: i3633.

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