P-441 a study in status of use and live birth rates of cryopreserved oocyte for social reasons
Authors: Okuyama N , Oka N , Aono N , Tsunoda M , Ishii M , Fukuoka Y , Koizumi A , Yoshinaga K , Hashimoto T , Kyono K 
Published: June 2022

Abstract

Study question
What is status of use and live birth rates of cryopreservation oocyte for social reasons?

Summary answer
11.2% of the cryopreserved oocytes were warmed and transferred, and the oldest of the successful live birth was 39 years old.

What is known already
More people nowadays tend to delay marriage and childbearing due to the social circumstances. It is now gradually known that the pregnancy rate decreases with increasing age, since the donation of gametes from third parties is regulated by the Japanese society, oocyte cryopreservation for social reasons has been becoming common practice. However, not much is known about the subsequent pregnancy and childbirth. Therefore, we conducted a survey on the use and clinical outcomes of cryopreserved oocytes for social reasons in our clinic.

Study design, size, duration
This retrospective single-center study was conducted with a total of 285 women, 424 cycles from March 2014 to December 2019. A total of 2696 oocytes were cryopreserved by vitrification. Written informed consent was obtained from all women who participated in this study.

Participants/materials, setting, methods
Ovarian stimulation was performed mainly with GnRH antagonist protocol. An injection of 5000IU of HCG was administered when the diameter of dominant follicle reached 18mm. All oocytes were denuded enzymatically with 80 IU/ml hyaluronidase, followed by mechanical denudation. The oocytes were then evaluated at metaphase II by confirming the presence of the first polar body. Mature oocytes were cryopreserved by vitrification. The partner's sperm was injected into the vitrified-warmed oocytes.

Main results and the role of chance
The age groups in the first freezing cycle were 30-34 years (7.4%), 35-39 years (49.8%), 40-44 years (37.2%), and 45 years and older (5.6%), respectively. The mean number of OPU cycles was 1.1±0.4, 1.4±1.4, 1.5±1.1, and 1.7±1.7. The average number of retrieved oocytes was 9.5 ± 5.4, 7.3 ± 4.5, 5.6 ± 4.6, and 2.2 ± 2.2. The total number of cryopreserved oocytes was 10.4±5.9, 10.4±7.1, 8.8±6.8, and 3.3±3.4. Sixty-seven women had partners after oocyte cryopreservation, and 33 women (49.3%) had oocytes thawed. The mean age at oocytes freezing was 39.6±2.6 years, and the mean age at thawing was 42.2±2.5 years. The oocytes survival rates, fertilization rates, blastocyst rates and clinical pregnancy rates per embryo transferred of vitrified oocytes were 92.7% (328/354), 69.5% (228/328), 43.9% (87/198) and 31.1% (19/61), respectively. Of these, 15 women (45.5%) became pregnant with vitrified-warmed oocytes, and 10 (30.3%) had livebirth. 18 women did not become pregnant with vitrified-warmed oocytes. Subsequently, 3 of the 18 women then became pregnant in ART (5.6%), by IUI (5.6%), or spontaneously (5.6%), respectively.

Limitations, reasons for caution
Not applicable.

Wider implications of the findings
Of the 33 cases, 10 (30.3%) successfully gave birth, indicating the usefulness of oocyte cryopreservation for social reasons. However, considering that most of our patients were already around 40 years old, awareness of the benefits of oocytes cryopreservation at younger ages and education of reproductive health and rights is essential.

Trial registration number
none