The World Health Organisation (WHO) has warned that tobacco use can undermine fertility in both women and men.

WHO gave the warning in a new publication issued on Tuesday, noting that “smoking very likely makes it harder to have a baby”.

The UN health agency said women who smoke have a 40 per cent higher risk of infertility than non smokers.

“For all people who plan pregnancies, our message is, ‘Stop smoking, improve your health, improve your reproductive health as well,’” said Dr Kerstin Schotte, Medical Officer, WHO Tobacco Free Initiative.

WHO defines infertility as the inability to achieve pregnancy after 12 months or more of regular unprotected sexual intercourse.

It said infertility affects about one in six people globally, across all regions and income levels.

“Many causes are outside our control, but tobacco smoking is one that isn’t,” WHO said.

The agency said decades of evidence had established a link between tobacco smoking and infertility in women.

It also warned that smoking could harm sperm quality and sexual function in men.

According to WHO, second hand smoke exposure may also affect fertility, exposing non smokers to possible reproductive risks.

The publication explained that quitting smoking could reduce the risk of infertility, with former smokers having a 25 per cent lower risk than those who continue to smoke.

WHO stressed that infertility was not solely a women’s issue, citing a review of 44 studies involving more than 60,000 men.

It said the review linked smoking to reproductive dysfunction, including semen abnormalities and sexual dysfunction.

The agency said men who smoke were more likely to experience erectile dysfunction, ejaculation problems, absence of sperm in semen, poor sperm motility and abnormal sperm shape.

WHO further warned that smoking could reduce the success of fertility treatment.

It cited earlier research involving 21 studies which linked cigarette smoking to fewer pregnancies and live births following assisted reproduction, including in vitro fertilisation (IVF).

The findings suggested that smoking could reduce the chances of successful fertility treatment outcomes by roughly half.

WHO also identified possible reproductive risks associated with waterpipe smoking, commonly known as hookah or shisha, particularly among men.

However, it said evidence on e-cigarettes, waterpipes, smokeless tobacco and other emerging nicotine products was still developing.

WHO said the available evidence suggested that other tobacco and nicotine products could also pose reproductive risks, but called for further research.

The agency also warned that exposure to second hand smoke could increase infertility risk among women by reducing the likelihood of conceiving each month.

WHO recommended that healthcare providers discuss the reproductive risks of tobacco use with individuals and couples planning pregnancy.

It also called for evidence based support to help tobacco users quit, including routine brief cessation advice in all healthcare settings.