Study	Reason for exclusion
Alhamdan 2007	Participants: couples planning to marry and applying for marriage licence Intervention: premartial screening programme for sickle cell and beta‐thalassemia Comparator: none Outcome: number confirmed sickle cell and beta thalassemia carriers, decision for marriage Design: observational, cross‐sectional study Excluded due to non‐RCT design
Bekker 1993	Participants: adults 18 ‐ 45 years Intervention: genetic carrier testing for cystic fibrosis Comparator: none Outcome: anxiety Design: observational, before and after intervention study Excluded due to non‐RCT study design
Castellani 2011	Participants: infertile couples undergoing cystic fibrosis screening as part of assisted reproduction process Intervention: genetic counselling via computer program Comparator: standard care genetic counselling session Outcome: knowledge Design: RCT Excluded because intervention was method of delivering genetic counselling and not preconception genetic carrier testing or screening compared to standard care
Cheuvront 1998	Participants: relatives of people with cystic fibrosis Intervention: home‐based pretest education from pamphlet with genetic test Comparator: clinic based pretest education via genetic counselling with genetic test Outcome: anxiety, knowledge, satisfaction, reproductive intent Design: RCT Excluded because intervention was method of delivering genetic counselling and not preconception genetic carrier testing or screening compared to standard care
Childs 1976	Participants: carriers of Tay‐Sachs disease identified prospectively or retrospectively during population screening Intervention: genetic carrier population screening Comparator: none Outcomes: knowledge, attitudes, anxiety, concerns, satisfaction Design: observational, cross‐sectional Excluded due to non‐RCT study design
Clayton 1996	Participants: non‐pregnant adults visiting clinical and non‐clinical sites Intervention: genetic carrier testing for cystic fibrosis Comparator: none Outcome: attitudes, beliefs Design: observational, before and after intervention design Excluded due to non‐RCT study design
Fisher 1981	Participants: adults carriers of beta‐thalassaemia 18 ‐ 65 years in a HMO Intervention: genetic counselling through video Comparator: conventional counselling by trained physician Outcome: knowledge, sexual activity, mood change, behaviour, anxiety Design: RCT Excluded because intervention is not preconception genetic carrier testing or screening
Hegwer 2006	Participants: adults of Ashkenazi Jewish background in prenatal and preconception settings Intervention: genetic carrier screening and education programme for Tay‐Sachs disease Comparator: none Outcome: knowledge, concern, attitudes, perceptions of genetic risk Design: observational, before and after intervention Excluded due to non‐RCT study design
Henneman 2001	Participants: adults aged 20 ‐ 35 years invited through Municipal Health Service or General Practitioner Intervention: genetic carrier screening for cystic fibrosis Comparator: none Outcome: knowledge, attitudes, understanding, satisfaction, psychological well‐being, uptake, worry, reproductive intentions, sharing of information Design: observational, before and after intervention Excluded due to non‐RCT study design
Honnor 2000	Participants: adults 18 ‐ 50 years in a primary care setting Intervention: genetic carrier testing and counselling for cystic fibrosis Comparator: none Outcome: anxiety, knowledge Design: observational, before and after intervention Excluded due to non‐RCT study design
Payne 1997	Participants: adults 16 ‐ 45 years in one primary care practice in South Wales Intervention: genetic carrier testing for cystic fibrosis Comparator: none Outcome: knowledge, anxiety Design: observational, before and after intervention Excluded due to non‐RCT study design
Tambor 1994	Participants: adults 18 ‐ 44 years in a HMO Intervention: invitation offering cystic fibrosis carrier screening and information giving either by personal education on‐site or by mailed brochure Comparator: none Outcome: attitudes, tolerance, utilization Design: observational, before and after intervention Excluded due to non‐RCT study design
Watson 1991	Participants: adults 16 ‐ 44 years from primary care practices and family planning clinics Intervention: genetic carrier testing for cystic fibrosis Comparator: none Outcome: anxiety, response to positive results, knowledge, reproductive intentions, behaviour Design: observational, before and after intervention Excluded due to non‐RCT study design
Wilkie 2013	Participants: adults 18 ‐ 35 years with sickle cell disease or sickle cell trait from clinics and community settings Intervention: web‐based multimedia educational intervention Comparator: usual care information e‐book Outcome: knowledge, reproductive intent and behaviour Design: randomised controlled trial Excluded because intervention was the delivery of education and not preconception genetic carrier testing or screening

HMO: health maintenance organisation RCT: randomised controlled trial