Thank you very much for your question. It is our pleasure to answer it.

Almighty Allah syas: 

And they ask you about menstruation. Say, "It is harm, so keep away from wives during menstruation. And do not approach them until they are pure. And when they have purified themselves, then come to them from where Allah has ordained for you. Indeed, Allah loves those who are constantly repentant and loves those who purify themselves." (Al-Baqarah 2:222) 

It is absolutely and categorically forbidden and prohibited for a believer to have sexual intercourse with his menstruating wife, unless and until the wife has first cleansed herself with a ghusl or full bath of purification after her period of menstruation.

The washing of the private parts of the woman or the mere performance of the wudu does not purify her from her impure state of menstruation; for the menstruating woman to be able to offer her prayers, or fast, or perform the tawaaf, or enjoy conjugal relations with her husband it is absolutely obligatory for her to first purify herself with a ghusl or full bath of purification.

If in ignorance of the Laws or Boundaries of Shariah one has enjoyed conjugal relations with ones menstruating wife before she has cleansed herself from her state of ceremonial or major impurity through a ghusl, one should turn unto their Lord in taubah and seek sincere repentance for their transgression..if they are indeed sincere in seeking repentance and amend their conduct thereafter, it is expected that they will find their Lord Forgiving and Merciful.

I hope this answers your question.