Influence of the ovarian hyperstimulation syndrome (OHSS) in embryo quality and in implantation and pregnancy rates

Abstract

OBJECTIVE: Some studies suggest that ovarian hyperstimulation can compromise implantation rates in assisted fertilization treatment cycles. Other studies believe that OHSS does not affect implantation rates or the quality of both oocytes and embryo. The purpose of this study was to evaluate embryonic quality, the implantation and pregnancy rates of patients with OHSS by comparing them to a control group without OHSS. DESIGN: Retrospective. MATERIALS AND METHODS: The study included 1905 patients with an indication for Intracytoplasmic sperm injection (ICSI) of which 156 patients had OHSS and 1749 did not (control group). Both the short and the long protocols were used. HCG was administered when at least 3 follicles had reached 19 mm in diameter. M2 eggs were injected 4 hours after oocyte retrieval. Fertilization and embryo development were assessed at 20h, 44h and 68h after ICSI. Embryo transfer was performed on day 2 or 3. Patients were divided into six groups, namely G1 (patients ≤ 35 years and with mild OHSS), G2 (patients ≤ 35 years and moderate or severe OHSS), G3 (patients between 36 to 40 years and mild OHSS), G4 (patients between 36 and 40 years and moderate to severe OHSS), G5 (patients ≤ 35 years without OHSS) and G6 (patients between 36 and 40 without OHSS). Statistical analyses used one-Way ANOVA or the Fisher's exact tests at the level of P<0.05. RESULTS: With respect to embryo quality, there was no statistically significance between the total of obtained embryos and the transferred embryos. The percentage of good morphology embryos (A+B) were: 75%, 82%, 73%, 88%, 78% and 78% for G1, G2, G3, G4, G5 and G6 respectively, and transferred embryos were: 95.5%, 100%, 98.5%, 100%, 98% and 97% for G1, G2, G3, G4, G5 and G6, respectively. Implantation rates were: 23% (G1), 56% (G2), 25% (G3), 45% (G4), 21% (G5) and 13.5% (G6). Hence, it was verified an increased implantation rate in G2 and G4 i.e., patients with a moderate or severe OHSS, as well as in the pregnancy rates, which were: 52% (G1), 72% (G2), 44% (G3), 71% (G4), 46% (G5), 47% (G6). CONCLUSIONS: Since no difference between the various groups was identified, our results do corroborate the opinion of certain authors who believe that embryo quality is not affected by OHSS. However, an increase in implantation and pregnancy rates was observed in both groups with moderate to severe OHSS i.e., G2 and G4 (≤ 35 years and 36-40 years, respectively).