Study	Reason for exclusion
Baber 1988	The participants in this study had achieved their pregnancies by in‐vitro fertilisation, which does not meet the selection criteria for this review.
Blumenfeld 1992	In this study, each patient was given information about the possibility of an increased rate of miscarriage in infertile patients and was able to choose whether to join the control or treatment arms. In cases where the patient was indifferent, they were prospectively randomised. The study therefore has to be excluded due to selection bias.
Nagpal 2001	This study also included patients with congenital malformations of the uterus as well as a those with a history of recurrent miscarriage. Progesterone and tocolytic agents were given to the control group and alongside human chorionic gonadotrophin in the treatment group. As such, there are confounding variables preventing this study from being comparable to the other trials.
Qureshi 2005	This study deals with threatened rather than recurrent miscarriage.
Shu 2002	This study observed the effects of Chinese herbal medicine plus human chorionic gonadotropin and progesterone in treating anticardiolipin antibody‐positive recurrent miscarriage.