Passing gas is natural and bound to happen.
If the relationship is just new, each of you might be holding it in or trying to hide it when it appears. However, eventually this behaviour can’t be hidden and nor should it have to be. I’m not suggesting to sit there letting them rip in front of each other, but if it happens don’t feel awkward or ashamed. If he is the one to break the relationship farting virginity first, don’t ignore it. Ignoring it could make the situation very awaked and send the message that you feel uncomfortable with farts.
Humour is always the best way to address situations like these. You could smile and make a joke about it or even say something witty like “babe happy to know our relationship is already at that comfortable point” But don’t let noise in front of each other go with nothing said. It can be awkward, but your reaction will help turn an awkward situation to a everyday and possibly humours one.