If Mary and Joseph could mutually abstain from coming together for more than 40 days before the birth of Jesus, they could certainly do so after.
25 And knew her not till she had brought forth her firstborn son: and he called his name JESUS.
And there was no reason at all for Mary to have sinned by with holding sex from Joseph.
Hebrews 13:4 Marriage is honourable in all, and the bed undefiled: but whoremongers and adulterers God will judge.
1 Corinthians 7:5 Defraud ye not one the other, except it be with consent for a time, that ye may give yourselves to fasting and prayer; and come together again, that Satan tempt you not for your incontinency.
Why would Mary or all people of placed her husband or herself in a position to be tempted by Satan?