Do pregnancies fathered by older men have more miscarriages?

This analysis looked at the risk of miscarriage with increasing paternal age. It found that pregnancies by fathers over age 40 had a higher risk of miscarriage.

Miscarriages are unfortunately common, with over 10% of recognized pregnancies and an estimated 30% of all pregnancies ending in miscarriage. In 50 to 70% of miscarriages, there are genetic abnormalities in the embryo or fetus.

Men produce sperm their entire lives. Germline cells in the testes divide to create sperm. Every time a cell divides, there is a chance that errors will occur in copying the DNA (genetic material). The cells can correct most of these errors. However as men age, the germ cells have undergone more divisions over their lifetime, and the repair mechanisms do not function as well. The sperm of older men are more likely to have mutations (DNA changes), breaks in their DNA, and abnormal chromosomes (sections of DNA).

It is well known that the age of the mother is connected to both genetic abnormalities and miscarriage. However, paternal age has been less studied, and most studies of maternal age have not adjusted for the age of the father. Older paternal age is related to stillbirth, birth defects, and autism. It is unclear whether the age of the father is connected to miscarriage risk.

This study reviewed 10 studies of paternal age and miscarriage. Seven of the ten studies found that paternal age had a significant effect on miscarriage. A study of 23,821 pregnancies found that fathers over 50 years had a 38% higher risk of miscarriage, compared to those aged 25 – 29.

The data from nine studies were pooled. Fathers aged 25 – 29 years were used as a comparison group. Fathers aged 40 – 44 years were associated with a 23% higher risk of miscarriage. Fathers over age 45 years were associated with a 43% higher risk of miscarriage.

Four of the studies looked at miscarriages in the first trimester of pregnancy. The combined data showed a significant relationship between age and early miscarriage. Fathers over age 45 years were associated with a 74% higher risk of early miscarriage.

Three of the studies looked at how maternal age related to miscarriage when paternal age was also taken into account. One study found that women over age 35 had a 52% higher risk of miscarriage when compared to those aged 25 – 29 years.

This analysis found that higher paternal age significantly increased the risk of miscarriage.

It is challenging to separate the effects of paternal age from those of maternal age. Also, this review did not include couples who used in vitro fertilization or other fertility treatments.