Stipulating a condition [about exiting ihram] in Hajj and ‘Umrah for one who is afraid that her menses may come

If a woman wants to do ‘Umrah but is afraid her menses may
come before she completes it, she may stipulate a condition [about exiting
ihram], then if she gets her menses she can exit ihram and will not have to
do anything. 

The basic principle about it being permissible to stipulate
such a condition is the report narrated by al-Bukhaari (5089) and Muslim
(1207) from ‘Aa’ishah (may Allah be pleased with her) who said: The
Messenger of Allah (blessings and peace of Allah be upon him) entered upon
Dubaa‘ah bint az-Zubayr and said to her: “Perhaps you want to do Hajj?” She
said: By Allah, I am always in pain. He said to her: “Go for Hajj but
stipulate a condition and say: O Allaah, I will exit ihram from the point
where You have prevented me (from continuing, if some problem should
arise).” 

If a person is afraid of illness or if a woman fears that her
menses may come, she may stipulate this condition. 

Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was
asked: With regard to stipulating a condition [about exiting ihram] in Hajj,
are there any specific cases in which the pilgrim should stipulate this
condition and say: “If something prevents me (from continuing), I will exit
ihram from the point where You have prevented me (from continuing)”? 

He replied: Stipulating a condition in Hajj means saying,
when entering ihram: “If something prevents me (from continuing), I will
exit ihram from the point where You have prevented me (from continuing).” 

Stipulating this condition is not prescribed unless there is
some fear of sickness, or if a woman fears that her menses may come, or if a
person is delayed and fears that he may miss Hajj. In these cases he or she
should stipulate this condition. If he stipulates this condition and
something happens that prevents him from completing the rituals, then he may
exit ihram and leave, and does not have to do anything. 

But if he is not afraid (of any of these things happening),
the Sunnah is not to stipulate a condition; rather he should be firm in his
resolve, put his trust in Allah and think positively of Allah, may He be
glorified and exalted. 

End quote from Liqa’ al-Baab al-Maftooh, 25/18 

And Allah knows best.