Study	Reason for exclusion
Abdelmassih 2002	Pooled oocytes and then randomised; no per woman data provided
Antinori 1996a	Not a randomised controlled trial Mentions randomly selected not randomly allocated
Antinori 1996b	No randomised comparison between control and assisted hatching groups
Balaban 2002	Not randomised No appropriate controls
Bider 1997	Not randomised
Blake 2001	Not randomised No embryo transfer occurred, so no review outcomes could be measured
Carter 2003a	No per woman data
Chao 1997	Assessment of pregnancy was by HCG only, 14 days after embryo transfer
Check 1996	Not randomised Benefits of AH confounded by concurrent assessment of 2 different culture media
Chen 1999	Not randomised Benefits of assisted hatching confounded by concurrent assessment of two different culture media
Cieslak 1999	Comparison of two types of assisted hatching; no 'no assisted hatching' control group was used More than one cycle per woman
Cohen 1990	Not randomised
Debrock 2011	Primary outcome was implantation, results per embryo transfer and not per woman
Demirol 2003	No pregnancy data provided
Dirnfeld 2003	No hatching
Dokras 1994	No appropriate outcome measure
Domitrz 2000	Benefits of assisted hatching confounded by concurrent assessment of two different culture media
Ebner 2002	No per woman data
Edirisinghe 1999	Not randomised
Feng 2009	Not a prospective study. A retrospective study
Figueira 2012	eggs were from egg donors, not the womens' own eggs
Frydman 2006	No per woman data
Gabrielsen 2004	Pseudo‐randomised (alternate days)
Grace 2007	No control. Comparing assisted hatching in good embryos with assisted hatching in poor embryos.
Hershlag 1999	Not randomised The control group were from the period 1990 to 1993, while the assisted hatching group were from 1994 to 1996 (historical controls)
Hiraoka 2009	No control. Comparing a half thinning versus a quarter thinning.
Hur 2011	Not clear if randomised, results appear to be per embryo transfer rather than per woman
Huttelova 1999	Not randomised Benefits of AH confounded by concurrent assessment of 2 different culture media
Komarovsky 2002	No per women data
Komarovsky 2003	No per women data
Lee 1999	Not randomised
Levron 2003	No per women data
Ma 2007	No per women data
Magli 1998	No per women data
Mahadevan 1998	Not randomised No concurrent controls
Mansour 2000	Randomisation by alternate days
Meldrum 1998	Not randomised No concurrent controls
Montag 1999	Not randomised No concurrent controls
Nagy 2003	No per woman data
Nakayama 1998	No appropriate outcome measure
Nakayama 1999	No per woman data
Ng 2008	No control. Compared 2 methods of laser
Obruca 1994	Not randomised No concurrent controls
Olivennes 1997	No per woman data
Peterson 2006	results per embryo transfer only no per woman data
Rienzi 2002	Assisted hatching was part of the ICSI method
Ringler 1999	It was not clear how many women were included in the study, or for how many cycles (only cycles were mentioned), and a mixture of participants and donated eggs were used for the study
Schoolcraft 1994	Not randomised Control and intervention groups recruited at different times
Shahin 2003	No per women data
Sifer 2005	Per cycle data only No per woman data
Szell 1998	Not randomised Benefits of assisted hatching confounded by concurrent assessment of two different culture media
Tao 1997	Not randomised Some of the women in the assisted hatching group were randomised, but most were allocated assisted hatching routinely, with no control option
Tucker 1991	Not randomised
Urman 2002	Alternate randomisation
Valojerdi 2008	Inadequate method of randomisation
Yano 2007	No per woman data, only per cycle data
Zech 1998	Numbers in tables do not add up correctly and the text and tables are contradictory on the age groups used in the prospective part of the study
Zhang 2009	Not a prospective study. A retrospective study.

HCG = human chorionic gonadotropin