The risk of infertility is 1.4 times higher in women who smoke, according to a systematic review of studies conducted between 2000 and 2026, according to a World Health Organization (WHO) report released on Tuesday.

“This means that if the risk of infertility is 15% for women who do not smoke, then 21% will experience infertility if they smoke,” the report explains. 

Women who smoke while trying to conceive have a higher risk of infertility or will take longer to conceive, according to the report. Meanwhile, women exposed to second-hand smoke had a 1.2 times higher risk of infertility.

Impact on men

While it is harder to quantify the effect of smoking on men’s fertility, a recent review of 44 studies involving over 60,000 men found that smoking was associated with “an increase in reproductive dysfunction”.

Across different populations, more men who smoked had erectile dysfunction and ejaculation problems than those who did not, the report notes.

The review also found that smoking may increase the risk of azoospermia (no sperm in semen), asthenozoospermia (poor sperm motility) and teratozoospermia (abnormal sperm shape).

E-cigarettes and hookahs

There is growing evidence of the impact of e-cigarettes on infertility. A study of over 4,500 women in the United States found that ever use of e-cigarettes was associated with a 20% reduction in fecundability.

Two studies that included women who smoked cigarettes or waterpipes (hookahs or shisha) found a similar increased risk of infertility, but no studies specifically address waterpipe use only.

Some studies have found that waterpipe smoking may be associated with lower sperm quality, such as less semen volume, lower sperm motility and fewer sperm with a normal shape. 

A recent study confirmed that hookah smoking may reduce sperm volume, but did not affect motility, so the WHO has recommended more research “to determine the effects of waterpipe smoking on sperm parameters in men”.

Impact on infertility treatment

Smoking may reduce the success of infertility treatments, but there is “some inconsistency across the studies”, according to the report. 

Research from 21 studies showed that cigarette smoking was linked to fewer live births and fewer pregnancies, “which indicate that the chances of successful treatment outcomes may be halved by cigarette smoking”, said the report.

However, “a more recent, albeit smaller, study involving about 300 women showed no differences in fertilisation or pregnancy rates between women who did and did not smoke cigarettes or between women who did or did not use e-cigarettes and/or waterpipes”.

The first report of a link between smoking and infertility was published in 1979 by the US Surgeon General, who reported that women who smoked were more likely to be infertile and experience abnormal menstruation and concluded that smoking may impair fertility.

Image Credits: Zaya Odeesho/ Unsplash.