Is there an association between oocyte number and embryo quality? A systematic review and meta-analysis.

This systematic review and meta-analysis determined the association between aspirated after ovarian stimulation and top/good quality embryos obtained in women undergoing ovarian stimulation for IVF/intracytoplasmic sperm injection (ICSI). MEDLINE, EMBASE, Scopus, CINAHL and Web of Science were searched for English-language publications on top/good-quality embryos at cleavage (day 2/3) and/or blastocyst (day 5/6) developmental stages, up to 18 November 2017. Twenty-eight studies (three prospective and 25 retrospective) reporting data on 291,752 assisted reproductive technology (ART) cycles were considered eligible. We confirmed a strong positive association between oocytes retrieved and top/good-quality day 2/3 embryos (weighted correlation coefficient [rw] = 0.791), day 5/6 embryos (rw = 0.901), metaphase II oocytes (rw = 0.988), oocytes exhibiting two pronuclei (rw = 0.987) and euploid embryos (rw = 0.851); P < 0.001 for all correlations (evaluated in subsets of the 17 studies). Data from 5657 cycles showed that the group with the most oocytes aspirated had the most top/good-quality day 2/3 embryos (pooled standardized mean differences (high [>15] versus low [<4] 1.91, 95% confidence interval [CI] 1.05-2.77, P < 0.0001; high versus medium [4-15] 1.15, 95% CI 0.74-1.55, P < 0.0001; medium versus low 1.41, 95% CI 0.79-2.03, P < 0.0001). Individual participant meta-analysis would enable accurate determination of these associations and other outcomes.

The relationship between sperm head retardance using polarized light microscopy and clinical outcomes.

In human sperm head, birefringence can be seen under polarized light resulting from highly ordered structures within the acrosome and nucleus. Selecting sperm with partial head birefringence improves success of clinical pregnancies in patients with severe male factor infertility. The aim of this study was to establish a range of retardance in sperm heads using polarized light microscopy to select an optimum sperm for intracytoplasmic sperm injection (ICSI). Sperm heads of 63 couples undergoing ICSI in women aged 38 years or younger were imaged at the time of ICSI and later analysed for retardance blinded to embryo and cycle outcomes. Sperm head retardance was similar irrespective of whether fertilization occurred. Quality of embryos on day 3 and day 5 were higher when sperm were selected with head retardance ranging from 0.56 nm or greater to 0.91 nm or less. Selection of sperm with head retardance ranging from 0.56 nm or greater to 0.91 nm or less was associated with higher clinical pregnancy rates (OR 3.74 95% CI 1.43 to 9.77). Optimum sperm for selection at the time of ICSI was with head retardance within the range 0.56 nm or greater to 0.91 nm or less.