Though much of the science we have about the effects of pesticides comes from studies on agricultural workers, these chemicals are plenty common around the home. They can be found out in the yard, in the garage, along the baseboards, and even on the plate of food on your dining table. The ways these toxins can impair fertility range from warping sperm DNA to causing miscarriages.
The best way to beat them is to avoid them. Flea and tick collars can be a source of insecticides that make their way wherever your pet goes—like your pillow. Look for natural alternatives, and bathe your pet and its bed often. Try organic options for lawn care and cleaning supplies. Keep critters out by keeping your house tight and tidy. If you do get an infestation, try baits and traps rather than chemicals. If it comes to needing an exterminator, be sure to find a licensed one, and ask about non-toxic options.
Source: "Proceedings of the Summit on Environmental Challenges to Reproductive Health and Fertility: executive summary," Fertilty and Sterility