The search identified 5331 hits. Following screening, 11 articles were included in the comparison of the long-acting GnRH agonist follicular protocol with GnRH antagonist protocol for analysis (Fig. 1). Among 11 studies included, 10 were observational studies (9 retrospective study; 1 prospective study) and one was a RCT (Supplementary table 2). There were nine Chinese and two English articles included in the analysis. The number of women in the agonist and antagonist arms were 1994 and 1678, respectively; the mean age in both the groups was 30.9 years. The proportions of normal ovarian responders, polycystic ovary syndrome (PCOS), and poor responders in each group were 69.2%, 27.1%, and 3.8%, respectively, in the agonist group and 42.5%, 46.5%, and 11.0%, respectively, in the antagonist group.
Quality Assessment and Publication Bias
Publication Bias
Publication bias of LBR, clinical pregnancy rate, and implementation rate depicted by funnel plots showed relatively lesser publication bias among the included studies for the long-acting GnRH agonist follicular protocol compared with the antagonist protocol. The funnel plot asymmetry for LBR (P = 0.35), clinical pregnancy rate (P = 0.49), and implantation rate (P = 0.75) was not statistically significant (Supplementary Fig. 1).
Primary Outcomes
Live Birth Rate
Of the 11 studies, only two reported live birth rate with a range of 45.8–46.6% in the agonist group and 21.2–29.7% in the antagonist group. Live birth rate was significantly higher in the long-acting follicular agonist group compared to the antagonist group (RR 1.61; 95% CI 1.27, 2.05) with the FE model, I2 = 0%, P = < 0.001 (Fig. 2).
Secondary Outcomes
Clinical Pregnancy Rate
All 11 studies [5, 14,15,16,17,18,19,20,21,22,23] provided data on clinical pregnancy rate, which varied from 40.0% to 76.9% in the long-acting follicular agonist and 27.3% to 63.2% in the antagonist protocols. Clinical pregnancy rate was significantly higher in the long-acting follicular agonist group compared to antagonist (RR 1.44; 95% CI 1.32, 1.58), P < 0.001 with the FE model, I2 = 0% (Fig. 3).
Implantation Rate
Six studies [5, 15, 19, 20, 22, 23] reported implantation rate, which varied from 33.33% to 61.4% in the long-acting GnRH agonist follicular group and 20.76% to 38.6% in the antagonist group. Analysis (FE model, I2 = 0%, P < 0.001) showed significantly a higher implantation rate among the women using the long-acting follicular agonist protocol compared to the antagonist protocol (RR 1.58; 95% CI 1.44, 1.73; P < 0.001) (Supplementary Fig. 2).
Miscarriage Rate
Among the eight [14,15,16, 18, 20,21,22,23] studies reporting miscarriage rate, the range in the long-acting GnRH agonist follicular was 5.0–22.2% and 0.00–18% in the antagonist protocol. There was no significant difference between the antagonist treatment group and long-acting follicular agonist group in the miscarriage rate with the FE model, (I2 = 0%, n = 8 studies) (RR 0.98; 95% CI 0.58, 1.64), P = 0.98 (Supplementary Fig. 3).
OHSS Rate
Among the seven studies [5, 14, 18,19,20,21, 23] that reported OHSS rate, three [5, 18, 21] reported total OHSS rate, three [19, 20, 23] reported moderate and severe OHSS rate, and one [14] reported severe OHSS rate. We combined them to analyze the OHSS rate, so the result was just a trend. In the long-acting GnRH agonist follicular protocol group, OHSS rate varied from 3.1% to 46.2%, whereas in the antagonist protocol the rate varied from 2.0% to 21.1%. The antagonist treatment showed a significantly lower OHSS rate compared to the long-acting follicular agonist protocol in analysis with the FE model (I2 = 0%, RR 1.63; 95% CI 1.15, 2.32; P = 0.0058) (Fig. 4).