Also of concern would be the number of infant life jackets you carry on board... On our 737's we can carry no more than 15 infants as thats how many infant life jackets we carry, but that number reduces depending on the load. With us, my understanding is that if you have a full load, then you can carry an extra 5% of the a/c capacity as infants - eg a 737-800 with 180 pax on board can carry 5% extra as infants - so thats 9 infants. But because a/c layouts vary so much, we have tables to refer to should the need arise!
And as far as infants pushing you over your cc : pax ratio, again its my understanding that the ratio of cabin crew to pax is based on the number of seats occupied
Cheers
