Timing of polar body extrusion is associated with body mass index, a pilot study using time lapse video microscopy

Abstract

To determine timing of oocyte maturation by observing polar body extrusion in a closed time lapse incubator system, as well as to correlate the observed times to patient derived factors. Retrospective Analysis. 21 patients (57 oocytes) undergoing either elective oocyte cryopreservation (OC) or intra-cytoplasmic sperm injection (ICSI) at our center were included in this study. Patients that had not signed research consent or if no immature oocytes were available after retrieval were excluded. 20 patients underwent gonadotropin/antagonist cycles and one patient underwent estrogen priming. Patients were triggered as per our protocol when the lead follicles were 18-19 mm and all follicles were retrieved at the time of egg retrieval. GV oocytes were then placed in a time lapse/stage top incubator which maintains constant temp of 37 degrees C and 5% C02 in air and 95% humidity levels as a conventional incubator. Images were obtained every 5 minutes for a total of 48 hours. All times were normalized to time of hcg trigger. Oocytes were left in Global for fertilization (Lifeglobal) media (G2), which is the media the oocytes were placed in after retrieval. Average age of all participants was 38.1 +/-3.4 years. Average baseline estradiol (E2) and follicle stimulating hormone (FSH) were 49.3 +/-14.6 (pg/ml) and 6.4+/-2 (mIU/ml) respectively. Average gonadotropin dosage (IU), E2 at trigger and number of oocytes retrieved were 3778.6 +/- 1576, 3349.3 +/-1334.7 and 21.9 +/-12.6, respectively. AMH and BMI were 3.34 +/- 2.1 and 20.1 +/- 8.5 respectively. Average time to oocyte polar body (PB) extrusion (in relation to trigger time) was 3495.3 +/- 253.9 minutes. Oocytes matured in 1104.6 +/- 274.5 minutes on average once placed in the time lapse incubator. 34/57 (60%) GV oocytes matured to metaphase 2 in vitro. Multiple linear regression revealed that the time to polar body extrusion was associated with BMI but not with AMH or percent of retrieved oocytes that were mature. Time to PB extrusion (TPBe) declined with BMI according to the equation: TPBe = -35.031 (BMI) + 4290.8 (minutes). Maturation rates of 60% were seen with the above protocol, which is comparable to published rates of IVM specific media. Although age and AMH did not show significance, higher BMI did show shorter maturation rates of GV oocytes in vitro. Further studies are needed to confirm these findings.