Table 1. Characteristics of Included Randomized Controlled Trials
Study (year) Patient population Protocol FET Luteal phase support + GnRHa Results
Davar et al. (2015) - Excluded women < 18 and > 40 years of age, oocyte recipients, systemic or endocrine disorders, endometriosis, submucous fibroids, intrauterine adhesions - Artificial cycle
- Embryo stage not reported - Mean number of embryos: 2.38 - 2.45
- Triptorelin 0.1 mg 3 days after transfer - Progesterone 800 mg suppo + estradiol valerate 6 mg + aspirin 80 mg CPR: 26% vs. 21%, p=0.40
Ong. PR: 22% vs.
17%, p=0.37
Imp. Rate: 14.66% vs.
13.07%, p=0.31
Abor. Rate: 5% vs. 8%, p=0.39
Chem. PR: 27% vs. 27%, p=1.00
Seikkula et al. (2016) - Excluded women age > 42 years, chromosomal abnormality, testicular or donated sperm used without female cause of infertility, donated oocytes used, congenital uterine anomalies, intramural myomas > 4 cm, submucous myoma, endometrial polyp > 1 cm, endometrium thickness < 6 mm before embryo transfer, blastocyst transfer, untreated thyroid dysfunction or hyperprolactinemia, allergy to triptorelin - Natural cycle
- Cleavage-stage embryos
- Mean number of embryos: 1.1
- Triptorelin 0.1 mg at age 6 days of the transferred embryos
- Progesterone 400 mg/day
LBR: 20.8% vs. 24.2%, p=0.481
CPR: 38.5% vs. 27.4%, p=0.199
PPR: 43.1% vs. 32.3%, p=0.212
Misc. rate: 12% vs. 1.8%, p=0.892
Extrauterine PR: 8% vs. 0%. p value N/A
Seikkula et al. (2018) - Excluded women age > 42 years, chromosomal abnormality, testicular or donated sperm used without female cause of infertility, donated oocytes used, congenital uterine anomalies, intramural myomas > 4 cm, submucous myoma, endometrial polyp > 1 cm, endometrium thickness < 6 mm before embryo transfer, untreated thyroid dysfunction or hyperprolactinemia, allergy to triptorelin - Artificial cycle
- Blastocyst embryos
- Mean number of embryos: 1.1
- Triptorelin 0.1 mg at age 6 days of the transferred embryos
- Micronized progesterone 600 mg vaginally
LBR: 29.2% vs. 19.4%, p=0.11
CPR: 40.3% vs. 36,1%, p= 0.693
PPR: 45.8% vs 41.7%, p = 0.691
Misc. rate: 27.6% vs. 42.3%, p=0.535 Extrauterine PR: 0% vs. 3.8%, p value N/A
Ye et al. (2019)

- Included women aged 20-37 years, BMI 28 kg/m2, 1 good quality embryo of day 3 after thawing

- Excluded oocyte recipients, uterine abnormalities, intrauterine adhesions with or without a history of previous surgery, endometrial thickness ≤ 7 mm on starting day of progesterone administration
- Artificial cycle
- A day 3 after thawing embryos
- Mean number of embryos: 2.0 ± 0.1
- Triptorelin 0.1 mg 3 days after transfer
- Progesterone 100 mg injection/day
Imp. rate: 41% vs. 39.2%, p=0.476
CPR: 57.7% vs. 58.7%, p=0.781
Ong. PR: 46.7% vs. 49.3%, p=0.478
Misc. rate: 11% vs. 9.9%, p=0.673
β-hCG rate: 68.8% vs. 68.4%, p=0.914
Wang et al. (2021) - Included women aged 20-45 years old, who have previous IVF/ICSI cycle, had at least 1-2 blastocyte-stage embryo(s) cryopreserved freezing, had undergone FET cycles
- Excluded women with infertility > 10 years, chromosomal abnormalities, hydrosalpinx, uterine malformations, submucosal myoma, history of tuberculosis or any uncontrolled endocrine disorder that may affect pregnancy, history of endometrial hyperplasia
- Natural and artificial cycles
- Blastocyst embryos
- Number of embryos: 1-2
- Triptorelin 0.1 mg on the day of transfer
- Other luteal support not clarified
CPR: 56.3% vs. 50.58%, p=0.086
Imp. rate: 39.98% vs. 38.01%. p=0.425
Biochem. PR: 15.87% vs. 18.94%, p=0.23
Ectopic PR: 0.43% vs. 0.69%, p=0.947
Abor. Rate: 10.43% vs. 12.01%, p=0.46
Ben-Ami et al. (2015) Patients undergoing a cleavage stage FET - Natural cycle
- Cleavage stage
- Number of embryos: ≥ 2
- Triptorelin 0.1 mg 3 days after transfer
- hCG 2,500 IU every 3 days x 4 injections
PR: 57.4% vs. 31.8%, p=0.02
CPR: 51% vs. 27.2%, p=0.029
Imp. rate: 25.2% vs. 13.6%, p=0.036

FET, frozen-thawed embryo transfer; GnRHa, gonadotropin releasing hormone agonist; BMI, body mass index; IVF, in vitro fertilization; ICSI, intracytoplasmic insemination; hCG, human chorionic gonadotropin; CPR, clinical pregnancy rate; Ong. PR, ongoing pregnancy rate; Imp., implantation; Abor., abortion; Chem. PR, chemical pregnancy rate; Biochem. PR, biochemical pregnancy rate; LBR, live birth rate; PPR, positive pregnancy rate; Misc., miscarriage; PR, pregnancy rate; N/A, not available.