Because older sperm tend to have more chromosomal mutations — ranging in seriousness from harmless to lethal — there is
among older fathers a higher rate of kids born with certain rare tumors, neural -
tube defects, congenital cataracts, and upper limb
defects.
The included birth
defects were based primarily on case reports of outcomes occurring in association with Zika virus infection during pregnancy; there is more evidence for some of these birth
defects than for others, and a causal link has not been established for all.5,10,12,21 - 27 Because much of the focus to date has been on microcephaly and brain abnormalities, data were summarized in 2 mutually exclusive categories: (1) brain abnormalities with or without microcephaly regardless of the presence of additional birth
defects and (2) neural
tube defects and other early brain malformations, eye abnormalities, and other consequences of central nervous system dysfunction
among those without evident brain abnormalities or microcephaly.