Richard Sharpe is a fertility researcher at the Queen's Medical Research Institute in Edinburgh, and he is the one responsible for conducting this type of research. He conducted a review of previous studies that were observing different factors that could influence the development of testicles while men were still in the womb and the connection with the sperm production later in life. Richard Sharpe claims that there is a growing evidence that prenatal exposure of males can have a major influence on the ability and capacity to produce sperm later in life, and he claims that the prenatal state is logically closely connected to the lifestyle of their mothers.
He claims that smoking during pregnancy is one of the biggest reasons for male fertility problems and sperm production later in life, and there are several large studies available that can back up these claims: in numbers studies claim that heavy smoking during pregnancy reduces sperm count by up to 40%. There are several other prenatal lifestyle factors that contribute to male infertility or reduced sperm production, and one of them that have the most negative impact are obesity and sedentary lifestyle.
Both obesity and sedentary lifestyle, accompanied by smoking, are not bad for the baby only, but are very damaging for the mother too. Pregnancy is truly the time when woman should take care of her body as much as possible and when she should quit all nasty habits such as smoking and alcohol or drug intake. She should pay special attention to healthy eating and moderate exercise. Prior pregnancy, when she is in a state of trying to conceive consciously she should also prepare her body in a way to normalize her body weight.