Put on ice twice: a problem Put on ice twice: a problem? Comparison of trophectoderm biopsy (Tebx) with preimplantation genetic screening (PGS) in cycles usiNg previously frozen vs. fresh autologous oocytes NYU Langone Fertility Center Nicole Noyes, Hsiao-Ling Lee, Sarah Druckenmiller, Patty Labella, Esmeralda Ampeloguio, James Grifo To resize boxes, click twice on the bottom box and drag the bottom of the box up or down. OBJECTIVE Independent use of oocyte cryopreservation (OC) & TEBX-PGS has rapidly increased over the past decade as these technologies have become more reliable and mainstream. Together they allow women to have children when ready and limit embryo transfer (ET) to a single euploid blastocyst (BL), even at advanced ages. Our center has performed >3000 cycles of each, and now uses the technologies together. Here, we assessed whether adding TEBX-PGS to OC impacted outcomes by comparing TEBX-PGS cycles in which previously cryopreserved vs. fresh (FR) oocytes served as the female gamete. TABLE. Outcomes of autologous ART cycles where TEBX-PGS was used. Values are n (%). RESULTS See Table/Graphs. Survival in OC cycles was >80%. In 93 OC (80%) and 1243 FR (86%) cycles, > one 2PN-fertilized oocyte developed into a BL suitable for TEBX (p= 0.1), with a mean of 4±3 BL/cycle for OC & 5±4 BL/cycle for FR (p=.01). When comparing OC to FR, a similar percentage of biopsied BL tested euploid or exhibited mosaicism. Regardless of oocyte age and freezing, transfer of 1 euploid BL resulted in similar implantation and pregnancy rates with >50% of transferred BL resulting in a live birth in all groups.   Age (y) < 40y OC (n=88; median age: 37±3.25 y; median MI & MII thawed: 14+10.7) < 40y FR (n= 857; median age: 37.5±5 y; median eggs retrieved: 14+11.3) P <40y groups > 40y OC (n=28; median age: 40+1.2 y; median MI & MII thawed: 12+15.5) > 40y FR (n= 589; median age: 41+3 y; median eggs retrieved: 9+8.8) >40y groups OC: Survived and Assessed as MII at Thaw 1004 (78% ) 281 (76%) No. Biopsied BL per 2PN Fertilization 288 (39%) 4320 (59%) .0001 87 (45%) 1877 (50%) .2 No. Euploid BL 97 (34% ) 1502 (35%) .8 10 (11%) 279 (15%) .4 No. Aneuploid BL 122 (42%) 1647 (38%) 68 (78%) 1255 (67%) .03 No. Mosaic BL 70 (25%) 1170 (27%) .3 9 (10%) 342 (18%) .06 No. TEBX Cycles with All Aneuploid BL  23 (32%) 176 (23%) .1 13 (65%) 314 (65%) 1 DESIGN Retrospective cohort study CONCLUSIONS OC was associated with fewer BL suitable for TEBX, but not a lower proportion of cycles with at least 1 biopsiable BL. Euploidy rate per biopsied BL, as well as implantation and ongoing/delivered rates per transferred euploid BL, were similar whether starting with cryopreserved or FR oocytes, regardless of age at retrieval. Thus, once the BL stage is achieved, outcomes with TEBX appear equivalent to FR. Furthermore, adding TEBX to OC appears potentially beneficial in affording single-ET and thus, singleton live birth. Patients should be counseled that OC may result in a lower BL formation rate and therefore, fewer biopsiable BL for evaluation. MATERIALS & METHODS 116 OC (n = 88 < age 40 + 28 ≥ age 40) and 1446 FR (n = 857 < age 40 + 589 ≥ age 40) cycles using TEBX-PGS performed @ NYU in 2015 & 2016 were assessed (mean age of both groups: 39±2y). Only PGS cycles using autologous oocytes retrieved at our center were included. In OC cycles, ICSI was performed on thawed mature (MII) oocytes; in FR cycles, ICSI or insemination was used based on semen parameters. All resultant zygotes were cultured for 5-7 days at which point any BL reaching Stage ≥ 2BC underwent TEBX & was then vitrified. Thus, in OC cycles, freezing occurred twice (oocyte + BL) while in FR cycles, only BL were frozen. In the OC arm, oocytes were cryopreserved for a median of 4±3y. Data were compared for OC vs. FR cycles in women < vs. ≥ age 40y. Chi Square was used for statistics. Funding statement and/or corresponding author contact information goes here.