Praise be to Allah.
We put this question to Shaykh Muhammad ibn Saalih al-‘Uthaymeen, may Allaah preserve him, who answered as follows:
It is not makrooh, because the Prophet (peace and blessings of Allaah be upon him) concluded the marriage contract with ‘Aa’ishah when she was six years old, and consummated the marriage with her when she was nine. The prospective husband may do that sometimes because he is keen to get married and is afraid that the woman or her family may change their minds, so he hastens to conclude the marriage contract. There is nothing wrong with that from the point of view of sharee’ah, but I think that the marriage contract should be concluded at the same time as the marriage is to be consummated, or shortly before, because that helps to avoid problems that may arise, such as differences that lead to divorce, or death of one of the spouses, etc… And Allaah is the source of strength.