Effects of the COVID-19 pandemic on maternal and perinatal outcomes: a systematic review and meta-analysis oleh Barbara Chmielewska, MBBChir, Imogen Barratt, BSc, Rosemary Townsend, MRCOG, Erkan Kalafat, MD, Jan van der Meulen, ProfPhD, Ipek Gurol-Urganci, PhD, Pat O'Brien, FRCOG, Edward Morris, FRCOG, Tim Draycott, ProfFRCOG, Shakila Thangaratinam, ProfMRCOG, Kirsty Le Doare, ProfPhD, Shamez Ladhani, ProfPhD, Peter von Dadelszen, ProfFRCOG, Laura Magee, ProfFRCOG, Asma Khalil, ProfMRCOG