Oocyte cytoplasmic diameter of ≥130 μm can be used to determine human giant oocytes.

OBJECTIVE

To determine if a cytoplasmic diameter of ≥130 μm can help identify human giant oocytes (GOs) in clinical practice and confirm the presence of genetic abnormalities in GOs by assessing the spindle length and centromere numbers.

DESIGN

Case-control study.

SETTING

Private in vitro fertilization clinic.

PATIENT(S): The subjects were women aged 20-49 years who underwent oocyte retrieval after ovarian stimulation from January 2014 to December 2020.

INTERVENTION(S): None.

MAIN OUTCOME MEASURE(S): The oocyte diameter was measured; immunofluorescent staining was performed to assess the spindle diameter and centromere numbers.

RESULT(S): Among the 254,337 oocytes examined, 561 (0.22%) had a diameter of ≥130 μm. The mean diameter ranges in the normal-sized metaphase II (MII) oocytes (MII group) and GO group were 103.0-119.0 and 132.3-175.9 μm. Spindle size could be measured in 6 GOs with 1 spindle (GO1), 10 GOs with 2 spindles (GO2), and 16 MII groups. The equatorial plane and pole-to-pole distance in the GO1 were significantly longer than in the GO2 and MII groups. The median numbers of centromeres were 86 in GOs with 1 spindle and 42 in each spindle for GOs with 2 spindles among 11 GO1s and 5 GO2s.

CONCLUSION(S): This study is the first to define GOs as oocytes with a diameter of ≥130 μm and is a large-scale study surveying the incidence of GO. It is also the first study to analyze and elucidate the relationship between spindle numbers within the cytoplasm of GOs and spindle size and centromeres.