Collection of metaphase oocytes at different time points.

<p>(A) MII COCs were harvested 15 hours after hCG trigger from oviducts. (B) The cumulus cells were removed from MII COCs. (C) MI COCs were harvested 6–7 hours after hCG trigger from ovaries. (D) The cumulus cells were removed from MI COCs. Scale bar = 50 μm.</p

Schematic illustration of treatments in FRESH-MII (Control 1), VW-MII (Control 2), V/W-AFTER-IVM, and V/W-BEFORE-IVM groups.

<p>The duration of oocyte maturation was 15 hours in all groups, which used hCG trigger as a set point. In FRESH-MII group, the freshly collected IVO MII oocytes were injected with a spermatozoa without any vitrification. In VW-MII Group, IVO MII oocytes were harvested 15 h after the hCG trigger from the oviducts, and those IVO MII oocytes were vitrified for later ICSI. In V/W-AFTER-IVM Group, cumulus cells were removed from MI oocytes, which collected 6–7 h after the hCG trigger from ovaries. After another 8 h of <i>in vitro</i> maturation, the oocytes with a PB extruded (IVM MI-II oocytes) were vitrified for later ICSI. In V/W-BEFORE-IVM Group, cumulus cells removed MI oocytes, which collected 6–7 h after the hCG trigger from ovaries, were vitrified for storage. After oocyte warming, the MI oocytes were <i>in vitro</i> matured for another 8 h, and the oocytes with a PB extruded (IVM MI-II) were regarded as mature oocytes for ICSI.</p

<i>In vitro</i> development of vitrified oocytes after ICSI.

<p><i>In vitro</i> development of vitrified oocytes after ICSI.</p

Preimplantation embryo development of FRESH-MII, VW-MII, V/W-AFTER-IVM and V/W-BEFORE-IVM oocytes following ICSI.

<p>(A) FRESH-MII oocytes. (B) MII-V/W oocytes after warming. (C) V/W-AFTER-IVM oocytes. (D) V/W-BEFORE-IVM oocytes. (E) Cleavage stage embryos derived from FRESH-MII oocytes. (F) Cleavage stage embryos derived from VW-MII oocytes. (G) Cleavage stage embryos derived from V/W-AFTER-IVM oocytes. (H) Cleavage stage embryos derived from V/W-BEFORE-IVM oocytes. (I) Blastocyst stage embryos derived from Fresh-MII oocytes. (J) Blastocyst stage embryos derived from VW-MII oocytes. (K) Blastocyst stage embryos derived from V/W-AFTER-IVM oocytes. (L) Blastocyst stage embryos derived from V/W-BEFORE-IVM oocytes. Scale bar = 100 μm.</p

<i>In vivo</i> development of vitrified oocytes after ICSI.

<p><i>In vivo</i> development of vitrified oocytes after ICSI.</p