Not much you can do but wait. When I applied for my infant, he got conditional approval right away. My friend had been waiting for a few months for her infant's c.a. and finally got it 2-3 days before their international back into the US.
I've heard of other independent data points (adults and children, including my own family) where the people waiting on c.a. finally get it a few days before a flight back to the US. And everyone just did interview on arrival.