Men who want to be fathers should go commando when they get some R&R, according to a new study.

National Institute of Child Health and Development and Stanford University researchers found that men who wear boxers during the day — and nothing when they sleep — had 25 percent lower rates of damaged DNA in their sperm compared to those who opt for tighty-whities during the day and at night.

The study was based on 500 men whose underwear choices and sleeping habits were tracked for up to 12 months before the quality of their sperm was analyzed.

“Type of underwear worn during the day and to bed is associated with semen quality,” according to this study.

“Better [sperm] quality parameters are observed in men wearing boxers during the day and none in bed.”

The research, presented recently at the annual meeting of the American Society for Reproductive Medicine in Baltimore, seems to replicate a 2012 British study that produced similar results.

“We have known for some time that men who increase the temperature of their testicles, either through the heat exposure at work or by wearing tight underwear, have poorer semen quality compared to men whose testicles are cooler,” said Allan Pacey, a leading fertility expert and researcher at the University of Sheffield in England.