For those suggesting cortisone, it is worthless for a torn meniscus. Absolutely not indicated. Physical therapy is also generally out for this sort of injury. It's a tear to the cartilage, which very rarely heals. It doesn't get better with rest, ice, and advil. OP now has a torn piece of cartilage; every time she bends her knee, it's rolling around, impinging the joint, potentially locking up (and probably making all sort of lovely popping and snapping sounds).
OP, if I were in your shoes, assuming this is a shave-down and they're not stitching it together (that recovery is a fate worse than hell), I'd go for it as soon as possible. It's a very easy recovery, back on your feet in a day or two, but I'd still want it out of the way before the baby is born.