title: Relevance of individual participant data meta-analysis for studies in obstetrics: delivery versus expectant monitoring for hypertensive disorders of pregnancy.
abstract: Like many other research subjects in obstetrics, research on immediate delivery versus expectant monitoring for women with hypertensive disorders of pregnancy faces certain challenges when it comes to interpretation and generalisation of the results; relatively rare outcomes are studied, in a clinically heterogeneous population, while the clinical practice in some countries has dictated that studies in term pregnancy were completed before earlier gestational ages could be studied. This has resulted in multiple smaller studies, some studying surrogate outcome measures, with different in- and exclusion criteria, and without enough power for reliable subgroup analyses. All this complicates the generation of definitive answers and implementation of the results into clinical practice. Performing multiple studies and subsequently pooling their results in a meta-analysis can be a way to overcome the difficulties of studying relatively rare outcomes and subgroups with enough power, as well as a solution to reach a final answer on questions involving an uncertain and possibly harmful intervention. However, in the case of the current studies on delivery versus expectant monitoring in women with hypertensive disorders of pregnancy, differences regarding eligibility criteria, outcome measures and subgroup definitions make it difficult to pool their results in an aggregate meta-analysis. Individual patient data meta-analysis (IPDMA) has the potential to overcome these challenges, because it allows for flexibility regarding the choice of endpoints and standardisation of inclusion and exclusion criteria across studies. In addition, it has more statistical power for informative subgroup analyses. We therefore propose an IPDMA on immediate delivery versus expectant monitoring for hypertensive disorders of pregnancy, and advocate the use of IPDMA for research questions in obstetrics that face similar challenges.
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Obstetrics and Gynaecology, The Netherlands. Electronic address: k.broekhuijsen@gmail.com.
authors.forename: Kim
authors.initials: K
authors.lastname: Broekhuijsen
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Epidemiology, The Netherlands.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bernardes
authors.affiliation: Department of Obstetrics and Gynaecology, Academic Medical Center, University of Amsterdam, The Netherlands.
authors.forename: Gert-Jan
authors.initials: GJ
authors.lastname: van Baaren
authors.affiliation: Department of Clinical Epidemiology, Biostatistics & Bioinformatics, Academic Medical Centre, University of Amsterdam, The Netherlands.
authors.forename: Parvin
authors.initials: P
authors.lastname: Tajik
authors.affiliation: Department of Obstetrics and Gynaecology, Frere Hospital, Walter Sisulu University, South Africa.
authors.forename: Natalia
authors.initials: N
authors.lastname: Novikova
authors.affiliation: Women's Health Research Unit, Centre for Primary Care and Public Health, Queen Mary University of London, United Kingdom.
authors.forename: Shakila
authors.initials: S
authors.lastname: Thangaratinam
authors.affiliation: Department of Obstetrics and Gynaecology, Bronovo Ziekenhuis, The Netherlands.
authors.forename: Kim
authors.initials: K
authors.lastname: Boers
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Obstetrics and Gynaecology, The Netherlands.
authors.forename: Corine M
authors.initials: CM
authors.lastname: Koopmans
authors.affiliation: Department of Obstetrics and Gynaecology, University of Mississippi Medical Center, United States.
authors.forename: Kedra
authors.initials: K
authors.lastname: Wallace
authors.affiliation: Division of Women's Health, King's College London Women's Health Academic Centre Kings Health Partners, United Kingdom.
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Shennan
authors.affiliation: Department of Obstetrics and Gynaecology, Atrium Medical Centre Parkstad, The Netherlands.
authors.forename: Josje
authors.initials: J
authors.lastname: Langenveld
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Epidemiology, The Netherlands.
authors.forename: Henk
authors.initials: H
authors.lastname: Groen
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Obstetrics and Gynaecology, The Netherlands.
authors.forename: Paul P
authors.initials: PP
authors.lastname: van den Berg
authors.affiliation: Department of Obstetrics and Gynaecology, The Robinson Research Institute, School of Paediatrics and Reproductive Health, University of Adelaide, Australia.
authors.forename: Ben Willem J
authors.initials: BW
authors.lastname: Mol
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Obstetrics and Gynaecology, The Netherlands.
authors.forename: Maureen T M
authors.initials: MT
authors.lastname: Franssen
mesh_terms: D000328:Adult; D002585:Cesarean Section / Q000009:adverse effects; D018450:Disease Progression; D005260:Female; D006801:Humans; D046110:Hypertension, Pregnancy-Induced / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D007231:Infant, Newborn; D007751:Labor, Induced / Q000009:adverse effects; D008297:Male; D057285:Precision Medicine; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D047928:Premature Birth / Q000453:epidemiology / Q000401:mortality / Q000517:prevention & control; D012306:Risk; D012720:Severity of Illness Index; D057832:Watchful Waiting
keywords: Hypertensive disorders of pregnancy; Individual patient data meta-analysis; Maternal morbidity/mortality; Perinatal morbidity/mortality; Preterm birth