The use of polarized light microscopy in IVF

Infertility is defined as the inability of a couple to conceive after 1 year of unprotected sexual intercourse. Approximately 15% of couples worldwide experience some form of infertility. The treatment of infertility with IVF has become an almost routine procedure for millions of couples experiencing infertility. The first IVF baby was conceived in 1978. By 2010 more than 4 million babies had been born as a result of assisted reproductive technology (ART). IVF involves stimulation of ovaries with FSH to produce multiple follicular development. When these follicles are appropriately developed, oocyte retrieval is undertaken under ultrasound control. The oocytes are then inseminated either by placing them with prepared semen in culture medium to allow fertilization to occur naturally (standard IVF) or by injection of individual oocytes with a single spermatozoa (intracytoplasmic sperm injection [ICSI]). The latter technique is used for significant male factor infertility, or for patients with previous poor fertilization rates or failed fertilization with standard IVF. Polarized light microscopy for viewing oocytes can only be used with ICSI since in this process the cumulus mass, which surrounds the oocyte, has been stripped away from the oocyte. Embryos are transferred transcervically to the uterus on day 2 or 3 after egg collection (four to eight cells) – termed the cleavage stage – or on day 5 (>100 cells) – termed the blastocyst stage. A pregnancy test is performed 16 days after oocyte retrieval. The selection of embryos with the highest implantation potential for transfer is one of the major challenges in ART [1]. Historically, multiple embryo transfer was used to maximize pregnancy rates. However, with improved embryo quality, multiple pregnancy rates increased with their associated potential risks of prematurity and cerebral palsy [2]. This has led to the necessity for a reduction in the number of embryos replaced. Thus, selection of the best embryo has become essential, especially now that elective single embryo transfer is recommended or even mandated in a number of countries. Traditionally, embryo quality assessment has been synonymous with and restricted to morphological evaluation using white light microscopy. Highly sophisticated systems of assessment have been developed, such as oocyte grading, first polar body morphology [3], pronuclear stage grading [4], embryo grading and Suha Kilani†2 and Michael G Chapman1