Author/Editor		Kovačič, Borut; Hojnik, Nina; Vlaisavljević, Veljko
Title		Effectiveness of different protocols for slow freezing of human blastocysts
Translated title		Učinkovitost različnih postopkov počasnega zamrzovanja človeških blastocist
Type		članek
Source		Zdrav Vestn
Vol. and No.		Letnik 80, št. Suppl 1
Publication year		2011
Volume		str. I-28-38
Language		eng
Abstract		Background: Pregnancy rate after the transfer of frozen / thawed human blastocysts has been lower in comparison with the pregnancy rate in vitro fertilization (IVF) cycles with fresh embryos. There is a need for the optimization of freezing protocols. Methods: In the years between 2000 and 2004, blastocyst culture was performed on 3087 IVF/ ICSI cycles. In the cases with more developed blastocysts one or two were transferred into the uterus. In 1031 cycles the surplus blastocysts were cryopreserved using one of four slightly modified two-step freezing, two-step thawing glycerol protocols. In protocol A (n = 41) we used a complex freezing medium (modified Ham F-12) and in the others (B, C, D) a simple one (without amino acids). In protocol B (n = 177) the blastocysts were thawed according to four-step thawing protocol. Protocol C (n = 81) retained two thawing steps. Protocol D (n = 37) was the same as C, but with the addition of hyaluronan into the freezing medium. Eight hundred thirty-four frozen blastocysts were thawed for transfer in 336 thawing cycles. In the retrospective study we compared survival according to blastocyst quality (in Groups B-D) as well as pregnancy and delivery rates between different protocol groups. We also compared the clinical outcome between the transfers of thawed blastocysts in natural (n = 249) or artificial cycles (n = 80). Results: The blastocyst survival rate does not differ between protocols B, C and D (68.7 % vs. 64.8 % vs. 69.8 %), but it was lower in Group A (53.2 %, P < 0.05). In groups B, Cand D, the morphologically optimal blastocysts survived cryopreservation in82.3 % vs. 81.1 % and 88.9 %, the suboptimal blastocysts survived in 67 % vs. 64.6 % and 64 % and poor blastocysts in 49 % vs. 48.7 % and 66.7 %, respectively. The clinical pregnancy rate was lower in Group A in comparison with Groups B, C and D (9.8 % vs. 21.5 % vs. 18.5 % vs. 16.2 %; P< 0.1). The mean delivery rate per thawing was 15.2 %. (Abs. trunc. at 2000 ch.)
Summary		Izhodišče: Metoda zanositve po prenosu zamrznjenih/odmrznjenih blastocist v maternico je še vedno manj uspešna v primerjavi z uspešnostjo postopka oploditve z biomedicinsko pomočjo s svežimi zarodki. Metodo zamrzovanja blastocist je zato potrebno izpopolniti. Metode: V obdobju od leta 2000 do 2004 smo v 3087 ciklih IVF/ICSI gojili zarodke do stadija blastociste. V ciklih z več blastocistami smo eno ali dve prenesli v maternico. V 1031 ciklih smo nadštevilčne blastociste tudi zamrznili po enem od štirih, delno razlikujočih se dvostopenjskih zamrzovalnih in odmrzovalnih postopkih z glicerolom. V postopku A (n = 41) smo kot osnovo za zamrzovanje uporabili kompleksno gojišče (prilagojeni Ham F-12), v ostalih postopkih (B, C, D) pa enostavno gojišče (brez aminokislin). V postopku B (n = 177) smo blastociste odtajali v štirih stopnjah. Pri protokolu C smo obdržali samo dve stopnji. Postopek D (n = 37) je bil enak postopku C, le da je gojišče vsebovalo še hialuronan. Odmrznili smo 834 blastocist v 336 ciklih. V retrospektivni raziskavi smo primerjali delež preživelih blastocist glede na njihovo kakovost (med protokoli B - D) ter delež zanositev in porodov med različnimi postopki zamrzovanja. Primerjali smo tudi klinične rezultate med prenosi zarodkov v naravnih ciklih (n = 249) in v umetnih ciklih (n = 80). Rezultati: Stopnja preživetja blastocist se med postopki B, C in D ni razlikovala (68,7 % oz. 64,8 % oz. 69,8 %). Nižja je bila le v skupini A (53,2 %, P < 0,05). V skupinah B oz. C in D so morfološko optimalne blastociste preživele zamrzovanje v 82,3 % oz. 81,1 % in 88,9 %, suboptimalne v 67 % oz. 64,6 % in 64 % in slabe blastociste v 49 % oz. 48,7 % in 66.7 %. Delež kliničnih nosečnosti je bil v skupini A nižji v primerjavi s skupino B,C in D (9,8 % oz. 21,5 % oz. 18,5 % oz. 16,2 %; P < 0,1). Delež porodov je bil v povprečju 15,2 %. (Izvl. skrajšan na 2000 zn.)
Descriptors		BLASTOCYST CRYOPRESERVATION SURVIVAL PREGNANCY