It is difficult for me say categorically whether or not oral sex lead to the amnionitis, unless the placental membranes were cultured and a swab taken from your husbands gums, and both showed the same bacteria with same type and strain. Amnionitis also occurs due to infection with viruses- not just bacteria. Also, if there has been rupture of membranes (leaking of bag of water), it can result in infection of membranes. Many times it is the infection of membranes that occurs first, followed by the abortion process. I would suggest that you wait for atleast 6 months to recover physically and emotionally from this abortion and get all possible tests done to know possible cause of abortion before planning the next pregnancy. Also, in the next pregnancy, please avoid all forms of sex in the initial 4 months.