| Study | Reason for exclusion |
|---|---|
| Al‐Shawaf 1993 | Retrospective study Comparing natural cycle FET versus GnRHa plus E2 plus progesterone No difference between the 2 interventions |
| Awonuga 1996 | Allocation to each intervention was not random but based on woman's choice. Comparing FET results following elective embryo cryopreservation in OHSS. FET done in natural cycle or in GnRHa plus oestrogen plus progesterone cycles. |
| Bals‐Pratsch 1999 | Uncontrolled study Case series of FET following E2 plus progesterone cycles |
| Belaisch‐Allart 1994 | Retrospective study Comparison of natural cycle FET, HMG ovulation induction FET and E2 plus progesterone FET |
| Benfer 1994 | Allocation to each intervention was not random Comparing results of natural cycle FET with GnRHa plus E2 plus progesterone FET No difference in outcomes between the 2 interventions |
| Chen 2007 | Retrospective study Comparison of natural cycle FET, GnRHa plus oestrogen plus progesterone FET, HMG FET and natural cycle plus HCG FET No difference in outcomes between the 4 interventions |
| Davar 2015 | Interventions not relevant: luteal phase support |
| de Ziegler 1990 | Allocation to each intervention was not random Comparing FET results in women who had IVF with women having FET using donated oocytes. IVF women with regular cycles were randomly assigned to natural cycle FET or GnRHa plus E2 plus progesterone FET cycles. IVF women with oligo‐ovulation were arbitrarily attributed to GnRHa plus E2 plus progesterone FET cycles. Women using embryos originating from donated oocytes had E2 plus progesterone FET cycles. |
| Dolan 1991 | Retrospective study Comparing natural cycle FET versus oestrogen plus progesterone FET No difference in outcomes between the 2 interventions |
| Dor 1991 | Allocation to each intervention was not random Comparing natural cycle FET (in the first 6 months of the study) versus HMG FET (in the second 6 months) versus oestrogen plus progesterone FET (in the last 7 months) No difference in outcomes between the 3 interventions |
| Elhelw 2008 | Interventions not relevant |
| Garrisi 1991 | Interventions did not meet inclusion criteria: compared success rate of fresh IVF cycle with success rate of thawed‐frozen embryos both in a natural cycle regimen |
| Gelbaya 2006 | Retrospective study Assessing natural cycle FET versus GnRHa plus oestrogen plus progesterone FET No difference in outcomes between the 2 interventions |
| Givens 2007 | A retrospective study Comparison of natural cycle FET versus oestrogen plus progesterone FET No difference in outcomes between the 2 interventions |
| Gonzalez 1992 | Retrospective study. Comparison of natural cycle FET versus oestrogen plus progesterone FET A trend of higher pregnancy rate in natural cycle FET was observed |
| Groenewoud 2015 | Interventions not reported |
| Imthurn 1996 | A quasi‐randomised study: allocation of intervention was based on presence or absence of spontaneous ovulation Natural cycle FET was allocated to women with a history of regular cycles while ovulation induction FET was allocated to women with anovulation history. Ovulation induction method was GnRHa followed by HMG. A trend towards fewer cancelled cycles was seen in the HMG FET group. |
| Jaroudi 1991 | Uncontrolled study Case series of FET following E2 plus progesterone cycles |
| Kawamura 2007 | Retrospective study Comparison of oestrogen plus progesterone FET versus natural cycle FET No difference in outcomes between the 2 interventions |
| Lee 2008 | Number of women randomized at baseline to each treatment group or number of women analyzed in each treatment group not reported |
| Lelaidier 1992 | Uncontrolled study Case series of FET following E2 plus progesterone cycles |
| Lelaidier 1995 | Uncontrolled study Case series of FET following E2 plus progesterone cycles |
| Loh 1999 | Non‐randomised study as allocation of intervention was based on presence or absence of spontaneous ovulation Ovulatory women had natural cycle FET while anovulatory women had oestrogen plus progesterone FET A significant higher live birth rate and a trend for higher clinical pregnancy rate in the natural cycle FET |
| Lornage 1990 | Retrospective study Comparison of natural cycle FET versus HCG‐induced ovulation cycle FET No difference in outcomes between the 2 interventions |
| Mausher 1991 | Uncontrolled study Case series of FET following GnRHa plus E2 plus progesterone cycles |
| Morozov 2007 | Retrospective study Comparison of natural cycle FET with oestrogen plus progesterone FET Significantly higher pregnancy rates in natural cycle FET |
| Oehninger 2000 | Non‐randomised study as allocation of intervention was based on presence or absence of spontaneous ovulation Ovulatory women had natural cycle FET while anovulatory women had E2 plus progesterone FET No difference in outcomes between the 2 interventions |
| Page 2005 | Interventions not relevant. Natural cycle versus FSH/HCG/progesterone |
| Pattinson 1992 | Non‐randomised study as women were given the choice of which type of FET cycle regimen to have Comparison of natural cycles FET with E2 plus progesterone FET No difference in outcomes between the 2 interventions |
| Queenan 1994 | Retrospective study Comparing natural cycle FET versus GnRHa plus E2 plus progesterone FET No difference in outcomes between the 2 interventions |
| Queenan 1997 | Uncontrolled retrospective study Analysing results of E2 plus progesterone FET |
| Sathanandan 1991 | Semi‐randomised study (quasi‐randomised) as women with irregular cycles, who had inadequate luteal function, women with amenorrhoea or oligo‐menorrhoea and women who were not pregnant in previous natural cycle FET were allocated to the GnRHa plus E2 plus progesterone intervention without randomization. Women having FET for first time and who had regular cycles were alternately allocated to either of the 2 interventions. Comparing GnRHa plus E2 plus progesterone FET with natural cycle FET No difference in outcomes between the 2 interventions except in women with oligomenorrhoea |
| Schmidt 1989 | Non‐randomised study as allocation of intervention was based on past history of ovulation disorder. Prospective comparison of oestrogen plus progesterone FET versus natural cycle FET A trend towards higher pregnancy rate was noted in oestrogen plus progesterone FET. |
| Shiotani 2006 | Not an RCT |
| Simon 1999 | Case series FET following E2 plus progesterone preparation |
| Spandorfer 2004 | Not an RCT |
| Tanos 1996 | Non‐randomised study as allocation of each type of intervention was based on presence or absence of regular ovulation. Women experiencing oligo‐ovulation were alternately offered ovulation induction or E2 plus progesterone endometrial preparation cycle. Prospectively comparing natural cycle FET versus GnRHa plus E2 plus progesterone FET versus GnRHa plus HMG FET No difference in outcomes among the 3 interventions |
| Taskin 2002 | Interventions not relevant |
| Wada 1992 | Non‐randomised controlled study as intervention allocation was based on couple's choice Comparison of natural cycle FET with GnRHa plus oestrogen plus progesterone FET No difference in outcomes between the 2 interventions |
| Yee 1995 | Retrospective study Comparing of GnRHa plus transdermal oestrogen plus progesterone FET versus GnRHa plus oral oestrogen plus progesterone FET versus oral oestrogen plus progesterone FET |
| Yishai 2001 | Retrospective controlled study Comparison of natural cycle FET with E2 plus progesterone FET No difference in outcomes between the 2 interventions |
| Yu 2015 | Interventions not relevant: administered different interventions within each treatment groups |
E2: 17 β‐estradiol; FET: frozen‐thawed embryo transfer; GnRHa: gonadotrophin releasing hormone agonist; HCH: human chorionic gonadotrophin; HMG: human menopausal gonadotrophin; IVF: in vitro fertilisation; OHSS: ovarian hyperstimulation syndrome; RCT: randomized controlled trial