(Abstracted from N Engl J Med 2019;380:1815–1824)
The hormone progesterone plays a critical role in preparing the endometrium for implantation of the embryo and continues to be produced throughout pregnancy. Historically, progesterone supplementation has been initiated during early pregnancies to prevent miscarriages in asymptomatic women who have a history of recurrent miscarriages or to rescue a pregnancy in women who have started to bleed during early pregnancy.
Tommy’s National Centre for Miscarriage Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham (A.C., A.J.D., V.C., H.H., L.J.M., I.D.G., H.W., A.K.E., T.R., C.C.O.); Faculty of Medicine and Health Sciences, University of Nottingham (J.P.D.), and Nottingham University Hospitals NHS Trust (S.D.), Nottingham; City Hospitals Sunderland NHS Foundation Trust, Sunderland (A.A., K.H.); Miscarriage Association, Wakefield (R.B.A.); East Lancashire Hospitals NHS Trust, Burnley (K.B.); Tommy’s Charity (J.B.), Guy’s and St. Thomas’ NHS Foundation Trust (T.H.), King’s College Hospital NHS Foundation Trust (J.J., J.R.), University College London Hospitals NHS Foundation Trust (K.K., D.J.), West Middlesex Hospital, Chelsea and Westminster NHS Foundation Trust (N.N., C.B.), and Barts and the London NHS Trust (A.S.), London; Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle (M.C.); Lancashire Teaching Hospitals NHS Foundation Trust, Preston (F.C.); MRC Centre for Reproductive Health, University of Edinburgh, Edinburgh (W.C.D., J.E.N., A.W.H.); Liverpool Women’s NHS Foundation Trust (L.W.) and St. Helens and Knowsley NHS Trust (S.R.), Liverpool; University Hospitals Coventry and Warwickshire NHS Trust, Coventry (F.I.); Department of Medicine, University of Glasgow, Glasgow (M.-A.L.); South Tees Hospitals NHS Foundation Trust, Middlesbrough (P.M.); University Hospitals Bristol NHS Foundation Trust, Bristol (C.E.O.); Biomedical Research Unit in Reproductive Health, University of Warwick, Warwick (S.Q.); Shrewsbury and Telford NHS Trust, Telford (M.U.); Portsmouth Hospitals NHS Trust, Portsmouth (N.V.); Surrey and Sussex Healthcare NHS Trust, Redhill (C.W.), United Kingdom; Melbourne School of Population and Global Health, University of Melbourne, Melbourne, VIC, Australia (I.G.); and Carver College of Medicine, University of Iowa Health Care, Iowa City, IA (A.E.)