To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
The corpus luteum (CL) is a transitory endocrine gland that develops from the postovulatory ruptured follicle during the luteal phase. Human chorionic gonadotropin (hCG), produced by the embryo, maintains the secretory activity of the CL due to its structural similarity to luteinizing hormone (LH) and subsequent activation of the same receptor. It maintains and stimulates the CL to produce estradiol (E2) and progesterone (P4). Luteal P4 is involved in the transition of the endometrium from a proliferative to a secretory type, with increasing decidualization – an essential facilitator of implantation  – and relaxation of the uterine muscle. Preparation of the endometrium lining the uterus for implantation of the embryo begins toward the end of a proliferative phase and extends throughout the luteal phase. This is important for the implantation process and maintenance of pregnancy until the placenta takes over steroid hormone production at approximately 7 weeks.
At the beginning of the menstrual cycle, there is an increase in bioactive follicle-stimulating hormone (FSH) levels, a stimulus for the growth and differentiation of follicular granulosa cells (GCs). GC steroidogenic enzymes are also inducible by FSH and are necessary for the production of estradiol (E2) and progesterone (P4), as well as expression of luteinizing hormone (LH) receptors on theca cells (TCs). LH then stimulates theca cells to produce androgens, which are metabolized to E2 by GCs under the influence of FSH. Elevated levels of E2 then inhibit FSH secretion, providing a negative feedback effect. Growth of the leading follicle continues owing to elevated levels of FSH receptors, whereas secondary follicles with fewer FSH receptors undergo atresia. Taken together, FSH and LH work in concert, as depicted by the classic two-cell (TC and GC), two-gonadotropin (FSH and LH) theory.
We aimed to assess whether the survival rate of embryos is influenced by the number of embryos/oocytes loaded on a single cryo-carrier during vitrification.
This was a retrospective study that included 974 patients who underwent thawing of 1896 embryo-warming cycles between September 2016 and January 2020. A distinct analysis was made for cleavage stage embryos (2–10-cell stage) and blastocysts. For vitrification, embryos were placed in a Cryotop™ open device using a SAGE vitrification kit following the manufacturer’s instructions. Warming was carried using a SAGE warming vitrification kit according the manufacturer’s instructions.
Total post-vitrification survival rates of embryos at the cleavage stage or blastocyst stage was 94.8%. At the cleavage stage, cryo-preserving three embryos per single cryo-carrier gave the highest full intact embryo survival rate (91.5%) compared with one or two embryo(s) per single cryo-carrier (85.7%, P < 0.0002 and 87.3%, P < 0.004). Conversely, post warmed full intact blastocyst survival rate for two blastocysts was significantly lower compared with one blastocyst (76.7% vs. 87.9%, P < 0.0193) per single cryo-carrier.
Post-thawing survival rate following vitrification is affected by the number of embryos per single cryo-carrier undergoing the vitrification equilibration phase, with the optimum number of three cleaved embryos or one blastocyst per single cryo-carrier. Further studies are required to determine the optimum number of cleaved embryos or blastocysts that should be loaded onto a single cryo-carrier vitrification device.
Email your librarian or administrator to recommend adding this to your organisation's collection.