Paternal age and assisted reproductive outcomes in ICSI donor oocytes: is there an effect of older fathers?

STUDY QUESTION Does paternal age affect semen quality and reproductive outcomes in oocyte donor cycles with ICSI? SUMMARY ANSWER Paternal age is associated with a decrease in sperm quality, however it does not affect either pregnancy or live birth rates in reproductive treatments when the oocytes come from donors <36 years old and ICSI is used. WHAT IS KNOWN ALREADY The weight of evidence suggest that paternal age is associated with decreasing sperm quality, but uncertainty remains as to whether reproductive outcomes are affected. Although developed to treat severe sperm factor infertility, ICSI is gaining popularity and is often used even in the presence of mild male factor infertility. STUDY DESIGN, SIZE, DURATION A retrospective cohort study spanning the period between February 2007 and June 2010. A total of 4887 oocyte donation cycles were included. PARTICIPANTS/MATERIALS, SETTING, METHODS Fertilization was carried out by ICSI in all cycles included, and the semen sample used was from the male partner in all cases. The association of male age with semen parameters (volume, concentration, percentage of motile spermatozoa) was analyzed by multiple analysis of covariance. The association of male age with reproductive outcomes (biochemical pregnancy, miscarriage, ongoing pregnancy and live birth rate) was modeled by logistic regression, where the following covariates were introduced: donor age, recipient age, semen state (fresh versus frozen) and number of transferred embryos (3 and 2 versus 1). MAIN RESULTS AND THE ROLE OF CHANCE We identified a significant relationship between paternal age and all sperm parameters analyzed: for every 5 years of age, sperm volume decreases by 0.22 ml (P < 0.001), concentration increases by 3.1 million sperm/ml (P = 0.003) and percentage motile spermatozoa decreases by 1.2% (P < 0.001). No differences were found in reproductive outcomes (biochemical pregnancy, miscarriage, clinical pregnancy, ongoing pregnancy and live birth) among different male age groups. LIMITATIONS, REASONS FOR CAUTION The use of donor oocytes, while extremely useful in highlighting the role of male age in reproductive outcomes, limits the generalization of our results to a population of young women with older male partners. No data were available on perinatal and obstetrical outcomes of these pregnancies. Most (75%) cycles used frozen/thawed sperm samples which might have introduced a bias owing to loss of viability after thawing. ICSI was performed in all cycles to control for fertilization method; this technique could mask the natural fertilization rate of poorer sperm samples. Furthermore, we did not use stringent ICSI indications; and our data are therefore not generalizable to cases where only severe male factor is considered. However, male patients were of different racial background, thus allowing generalizing our results to a wider patient base. WIDER IMPLICATIONS OF THE FINDINGS Our study suggests that paternal age does not affect reproductive outcomes when the oocyte donor is <36 years of age, indicating that ICSI and oocyte quality can jointly overcome the lower reproductive potential of older semen. STUDY FUNDING/COMPETING INTERESTS This study was supported in part by Fundació Privada EUGIN. The authors have no conflicts of interest to declare.