On Preventing Pregnancy

The answer—and Allah is the One who grants success: It appears that using an IUD to prevent pregnancy requires the woman, in using it, to uncover the most private part (al-ʿawrah al-mughallaẓah), since it is placed inside the vagina. Therefore, a woman should use for preventing pregnancy a medication that does not require uncovering the private part. If, however, using such medication is harmful and necessity compels the use of an IUD, then there is no harm in using it.
What we have said is indicated by His—Exalted is He—saying: "…except what you are compelled to [consume]." [Al-Anʿām:119], and by His saying: "Allah intends for you ease and does not intend for you hardship." [Al-Baqarah:185], and "He has not placed upon you in the religion any hardship." [Al-Ḥajj:78]; and by the well-known report: “In cases of necessity, the prohibited becomes permissible.”
As for using medications that do not require uncovering the private part—these may be used without necessity, whether the husband permits or not. This is the madhhab, as in al-Bayān.
Source : Min Thimār al-ʿIlm wa al-Ḥikmah vol.1