Women who are experiencing miscarriages after 6 months to 1 year typically had their husbands with low sperm counts. The research indicates that one-half of 1% of men was functionally sterile in 1938. Today it has increased by 15-fold. Functionally sterile is defined as sperm counts below 20 million per milliliter of semen.
The age of the male partner has significant impact on reproduction. Male fertility starts to decline after 40 when sperm quality decreases. Studies have consistently shown that increasing male age is associated with an increased time to pregnancy and decreased pregnancy rates.