Smokers less likely to have boys – sperm damage blamed

Friday 19 April 2002

ASH news release:  19 April 2002 immediate

A new study of almost 12,000 infants and their parents shows that smokers are more likely to have baby girls than boys and that damage to sperm is the likely cause [1][2].

The researchers found the sex ratio was 1.21 boys to every girl in the group in which neither parent smoked.  However, it fell to 0.82 boys to every girl in the group where both mother and father smoked more than 20 cigarettes a day.  The researchers suggest that the sperm cells carrying the male Y chromosome are more vulnerable to the toxins in cigarette smoke.

Clive Bates, Director of ASH, said:

“This is very troubling for anyone thinking about having kids, and it adds the catalogue of insidious reproductive disorders caused by smoking.

“People think it’s just cancer and heart disease caused by smoking and that these are something that happens to people later in life, but this shows that smoking is doing subtle damage to people right from the age they are having children.”

“I suppose a few people will say that couples that want a girl should smoke like mad, but I think that would be a very dangerous thing to do given all the other things that smoking can do to the reproductive system.”

ASH pointed out that smoking was already understood to be a cause of reduced fertility, low-birthweight and other complications, spontaneous abortion, decreased sperm density and motility, delayed conception [3] and male sexual impotence [4].  On top of this there are problems associated with passive smoking exposure once the child is born and that is know to be a cause of respiratory problems, middle ear infection and cot-death [5].

Clive Bates added:

“Whether a couple want a boy or a girl or would be happy with either, one of the best things they can do for their baby and for themselves is to quit smoking.”


More information

[1] Fukuda M. et al. Parental periconceptional smoking and male: female ratio of newborn infantsThe Lancet, Volume 359, Issue 9315, Pages 1407 – 1408, 20 April 2002

[2] BBC report: “Smokers have more baby girls”

[3] ASH fact sheet: Smoking and reproduction (pdf)

[4] ASH & BMA report: “Smoking and male sexual impotence” (pdf)

[5] ASH Research Report: Impact of secondhand smoke on children (pdf)


Contact: Clive Bates 020 7739 5902 (work) or 077 6879 1237 (mobile).  ISDN available.