[soitlyobserty]

A General view of the WTA on the subject

In the event that the gender of a player is questioned, the medical
delegate (or equivalent) of the WTA shall have the authority to take
all appropriate measures for the determination of the gender of a
player. The results of any tests conducted will not be made public,
but will be reported to the WTA Legal Department who shall
advise the Board of Directors of the gender of the player concerned.
Failure by a player to submit to testing upon the request of the
WTA shall subject the player to immediate suspension from competition
until such time as the appropriate testing is carried out in
accordance with this rule. All tests will be at the expense of the
player.
b. Transsexuals
Any individuals undergoing sex reassignment from male to female
before puberty are regarded as girls and women (female), while
those undergoing reassignment from female to male before puberty
are regarded as boys and men (male).
Individuals undergoing sex reassignment from male to female after
puberty are eligible for participation in WTA Tour Tournaments
under the following conditions:
i. Surgical anatomical changes such as gonadectomy have
been completed, including external genitalia changes;

ii. Legal recognition of the female gender has been conferred by
the appropriate official authorities;
iii. Hormonal therapy appropriate for the female sexual assignment
has been administered in a verifiable manner and for a
sufficient length of time to minimize gender-related advantages
in sport competitions; and
iv. Eligibility should begin no sooner than two (2) years after
gonadectomy.
In all instances, a confidential case-by-case evaluation will occur
Source: WTA Rulebook page 24-25