Table 1.
Description of identified trials examining effectiveness of single embryo transfer (SET) versus double embryo transfer (DET)
| Authors | Details | Interventions | Clinical outcomes |
|---|---|---|---|
| Included published trials | |||
| Gerris et al, 199929 | First IVF/ICSI cycle. Female age <34. At least one top quality embryo should be available | SET fresh v DET fresh | Clinical ongoing pregnancy (at least one gestational sac with heartbeat), multiple pregnancy, biochemical pregnancy (positive test), implantation, clinical miscarriage (loss of at least one amniotic sac identified at sonography), clinical ectopic pregnancy (required surgical intervention) |
| Lukassen et al, 200527 | First IVF/ICSI cycle. Female age <35. FSH <10I U/L. At least one good quality embryo should be available | SET fresh + SET fresh v DET fresh | Cumulative live birth, singleton live birth, multiple live birth, clinical ongoing pregnancy (at least one gestational sac with heartbeat), abortion, ectopic pregnancy, preterm birth (<37 weeks’ gestation), low birth weight (<2500 g), perinatal death rates and live birth rate after only one treatment cycle |
| Martikainen et al, 200130 | Fresh IVF/ICSI treatment in four centres. No more than one previous failed treatment. Age was not taken into account and first two cycles eligible in two centres. In other two centres, age <36 in first cycle only. At least four good quality embryos should be available | SET fresh v DET fresh | Live birth, singleton live birth, twin live birth, clinical pregnancy (confirmed by ultrasonography), implantation, miscarriage, ectopic pregnancy, preterm birth (<37 weeks’ gestation), low birth weight (<2500 g) rates |
| Thurin et al, 200426 | First or second IVF cycle. At least two good quality embryos available for transfer or freezing. Female age <36 | SET fresh + SET frozen v DET fresh | Cumulative live birth, biochemical pregnancy (positive test), implantation (number of gestational sacs/number of embryos transferred), multiple live birth, spontaneous abortion, ectopic pregnancy |
| Van Montfoort et al, 200628 | First IVF cycle. Participants had to have normal fertilisation of at least two oocytes (two pro-nuclear stage embryos) irrespective of woman’s age or embryo quality | SET fresh v DET fresh | Biochemical pregnancy (positive test), clinical pregnancy (at least one gestational sac with heartbeat at 12 weeks’ gestation), twin pregnancy, abortion |
| Included unpublished data | |||
| Thurin. Elective single embryo transfer [dissertation]. Gothenburg University, 20059 | Female age ≥36 years. First or second IVF/ICSI cycle. At least two good quality embryos available | SET fresh + SET frozen v DET fresh | Cumulative live birth, biochemical pregnancy (positive test), implantation (number of gestational sacs/number of embryos transferred), multiple live birth, spontaneous abortion, ectopic pregnancy |
| Davies M. Australian study of single embryo transfer (ASSET) | Female age <35 if no previous ART pregnancy, <40 if previous ART pregnancy. At least four good quality embryos or at least three if previous ART pregnancy successful | SET fresh versus DET fresh | Cumulative live birth, twin live birth, clinical ongoing pregnancy (fetal heartbeat), complications during pregnancy, delivery and neonatal period, perinatal mortality and morbidity, use of neonatal intensive care |
| Bhattacharya S. Efficacy and cost effectiveness of selective single embryo transfer (ECOSSE)10 | Female age ≤37. First or second IVF/ICSI cycle. At least four good quality embryos at time of embryo transfer | SET fresh + multiple SET frozen v DET fresh + multiple DET frozen | Cumulative live birth, twin live birth, clinical pregnancy (at least one gestational sac with heartbeat), biochemical pregnancy (positive test), miscarriage, ectopic pregnancy preterm delivery, low birth weight, congenital abnormality |
| Excluded trials | |||
| Gardner et al, 200424 | Involved only blastocyst (day 5) transfers | SET fresh v DET fresh | Clinical ongoing pregnancy (at least one gestational sac with heartbeat), twin pregnancy, implantation (number of gestational sacs with heartbeat/number of embryos transferred) |
| Heijnen et al, 200723 | Different ovarian stimulation protocols used in two arms | Mild ovarian stimulation (GnRH) antagonist co-treatment) + SET fresh + SET/DET frozen as per patient’s preference v standard ovarian stimulation (GnRH agonist long protocol) + DET fresh + SET/DET frozen as per patient’s preference. More than one fresh cycle | Cumulative term (≥37 weeks’ gestation) live birth, term singleton live birth, late preterm (32-37 weeks’ gestation) live birth, early preterm (< 32 weeks’ gestation) live birth, clinical pregnancy (positive heartbeat) rates within 1 year of randomisation. Multiple pregnancy. Time to pregnancy leading live birth |
| Moustafa et al, 200825 | Quasi-randomised trial with alternate days used as method of randomisation | SET fresh + multiple SET frozen v DET fresh + multiple DET frozen | Live birth, clinical pregnancy (positive heartbeat), multiple pregnancy. Gestational age at miscarriage, gestational age at birth, birth weight |
IVF=in vitro fertilisation; ISCI=intracytoplasmic sperm injection; FSH=follicle stimulating hormone; SET=single embryo transfer; DET=double embryo transfer; GnRH=gonadotrophin releasing hormone; ART=assisted reproductive technology.