Can a woman go for internal pelvic ultrasound? What will be the status of fasting then?
In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
An internal pelvic ultrasound involves a probe being inserted into the female private part.
The early Fuqahā’ had enumerated the private part to be one of those entry points which can invalidate a fast. This was based on the understanding that the female private part is connected to the digestive system.
However, contemporary Fuqahā’ have opined that since the female private organ has no connection to the digestive system, the fast should not break by inserting something therein. The digestive system here refers to the throat, intestines and stomach. This conclusion is based on the principles laid down by the earlier Fuqahā’. Mufti Rafi` ‘Uthmani Hafidhahullah has discussed this issue in great length and depth in his al-Maqālāt al-Fiqhiyyah.
Thus, the following openings to the body are invalidating entry points and substances entering and traversing therein will consequently reach the digestive system:
1) The mouth
2) The nose
3) Perforated eardrums
4) The anus
Therefore, by having an internal pelvic ultrasound whilst fasting, the fast will not be invalidated.
And Allah Ta’ālā Knows Best
Mufti Faraz Adam,
 المقالات الفقهية ص 113-124 مكتبة دار العلوم
The Fuqahā’ have based the ruling of how fasts are invalidated on something known as jawf. On discussing jawf, linguists such as Ibn Manẓūr, al-Jawharī and others described it as the internal part which can be empty or full.
There are many such jawf found in the human body, for example, the stomach, intestines, heart, bladder, womb etc. However, the Fuqahā’ were referring to a specific jawf, namely, the stomach, throat and intestines which are part of the digestive system. This was called al-Jawf al-Mu`tabar (the considered internal section).
Imam Abū Hanīfah raḥimahullah was of the opinion that a woman’s fast would be invalidated by inserting something into the front private part. This was based on medical research of that time suggesting that the front private part and the digestive system are connected.
Imam Abū Yūsuf rahimahullah was famously of the opinion that anything entering the urethra will invalidate the fast. He believed that the bladder was connected to the digestive system.
Imam Sarakhsī, Imām al-Marghīnānī, Imām ibn al-Humām, Imām Ibn Nujaym and others have stated the above opinions are all based on medical research and not fiqh per se.
Contemporary medical research has proven that the front female private part leads to the womb and the bladder, which are not connected to al-jawf al-mu`tabar.
Hence, the contemporary Fuqahā’ of the Hanafī school have stated that the female private part will not be considered as an entry point leading to the jawf and invalidating the fast.
This answer was collected from DarulFiqh.com, which is operated under the supervision of Mufti Faraz ibn Adam al-Mahmudi, the student of world renowned Mufti Ebrahim Desai (Hafizahullah).