Fertility testing can be done.
For males, a sperm count can be performed.
For females, an internal exam is usually performed along with blood work, to test hormone levels.
STD's can make it more difficult for someone to get pregnant, usually because the infection causes scarring of the fallopian tubes. Chlamydia is one such STD. If caught early the damage can heal. The problem arises since most people, men and women, don't exhibit any symptoms.
In-vitro can be an option. Sperm can be obtained and used to fertilized an egg, either from the parent or a donor, then it is fertilized and implanted.
Hope it helps. Post back if you have another/further questions.