This is not exactly why we encourage random drug testing.

The availability of medical marijuana, employee use of heavy equipment, the opioid "epidemic," and many other problems lead employers to require random drug testing.  Such testing has to be truly random and not administered in a discriminatory fashion so as to remain compliant with statutes such as the Americans with Disability Act.  (See here for how the EEOC suggests handling such testing.)

Drug testing is not ordinarily used to determine whether an employee is pregnant.  To do so would clearly violate Title VII as gender based discrimination "because of sex."  (And not just because pregnancy is almost always because of sex, but I digress).

But when an Australian basketball pro failed a drug test  he found himself banned from the game because the test concluded that he was pregnant.

No, of course he wasn't really pregnant.  Seems that he had submitted his girlfriend's urine sample instead of his own, while she was blissfully ignorant of the fact that she was pregnant.

Surprise!  You're going to be a daddy!  Surprise!  You're fired!