Age-related changes in sperm output develop gradually without any evidence of sudden onset. Female fecundity starts to decline after 30 years of age and is greatly reduced after age 40 years. The effect of male age on fecundity remains controversial and few studies show a similar trend in men. The effect of ageing of the male partner on the risk for miscarriage has been studied extensively, although many studies are retrospective, span long observational periods and fail to control properly for maternal age effects, or have small sample sizes. The Royal College of Obstetricians and Gynaecologists (RCOG) recommends the British Andrology Society guideline of limiting the age of sperm donors to 40 years. Paternal ageing does not affect the risk of miscarriage, and increased paternal age on its own is not an indication for prenatal diagnosis since the absolute risk for genetic anomalies in offspring is low.

Embryo cryopreservation is crucial for both the efficiency and the safety of assisted reproduction treatments. The potential risks of damage for cryopreserved-thawed embryos include exposure to medium biochemical contaminants, ice crystal formation within the embryo, toxic effect of cryoprotectants, damage during thawing process, physical damage during embryo manipulation, and DNA damage during embryo storage; but freezing itself cannot be considered a mutagenic procedure. Conventional embryo freezing concerns multicell embryos. Cryopreservation of early-stage embryos can be considered a valid alternative to conventional embryo cryopreservation. Cryopreservation of unfertilized oocytes presents more technical problems than early-stage embryo cryopreservation. The most alarming risk related with oocyte cryopreservation is aneuploidy in embryos conceived with this method. Children born from cryopreserved oocytes should be accurately monitored to ascertain the correct growth and development and to exclude possible genetic anomalies and malformations.