Until recently, little was known about the effects of alcohol, tobacco, marijuana, cocaine and other drugs on a man's reproductive system and the ability to father children. Scientists are finding that when certain drugs enter the testicles through the bloodstream, a man's sperm count is lowered and the sperm's motility or ability to swim is diminished.
Damaged sperm can cause a pregnancy to end in miscarriage.
Drugs can interfere with reproduction by changing the process by which sperm are selected for fertilizing the egg. The drugs in a man's system can lead to lower birth weight, birth defects or serious illnesses for the child after birth. Studies show that a man's drinking patterns before conception of a child can influence the health of future children. The use of alcohol by men prior to conception may result in physical problems in offspring which may not show up until the child is several years old. Heavy alcohol use by the male before conception can be linked to infertility, altering of the reproductive chemistry, low birth weight, and subtle, long-term, permanent damage in the child.