In a study, researchers found that a mother's smoking during early pregnancy dramatically reduces the numbers of germ cells (the cells that form eggs in females and sperm in males) and somatic cells (the cells that form every other part of the body) in the developing foetus. They believe that this may have an adverse effect on the fertility of the baby in later life.
In a second study, researchers looked at specific proteins called protamines in the sperm of men who smoked and compared them with the protamines in non-smokers.
Role of protamines
Protamines play an important role in the development of sperm – they are necessary for the process that results in the formation of chromosomes during cell division – and, therefore, have an effect on subsequent male fertility.
The research was published online in the journal Human Reproduction recently.
For the first study, Claus Yding Andersen, Professor of Human Reproductive Physiology at the University Hospital of Copenhagen (Denmark), and his colleagues looked at 24 embryonic testes obtained after women had undergone legal termination between 37-68 days after conception. They also took blood and urine samples and questioned the women about their lifestyle during pregnancy, including smoking and drinking habits.
They found that the number of germ cells was more than halved (reduced by 55 per cent) in the testes of embryos from mothers who smoked compared with those from the non-smoking mothers.
Somatic cell reduction
The number of somatic cells was also reduced by more than a third (37 per cent). The effect was dose dependent, with a greater reduction in germ and somatic cells being seen in embryos from the mothers who smoked the most. This remained the same, even after adjusting for coffee and alcohol consumption.
When these results were added to their earlier work that looked at the effect of smoking on 28 female embryos, the researchers found that, overall, germ cells in the ovaries and testes of embryos exposed to smoking were reduced significantly by 41 per cent compared with the number of germ cells in non-exposed embryos. The results also showed that germ cells were more susceptible to damage caused by smoking than somatic cells.
Prof Andersen said: “As the germ cells in embryos eventually develop to form sperm in males and eggs in females, it is possible that the negative effect on the numbers of germ cells caused by maternal smoking during pregnancy may influence the future fertility of offspring.
In addition, the reduction in the number of somatic cells also has the potential to affect future fertility, as somatic cells in the testes support the development of germ cells to form functional sperm.
If the somatic cell number is reduced, fewer functional sperm will be produced.”
