There isn't really a set number whether it's their first litter or not. Average Bichon litter is about 2 to 5 pups though can be less or more. Someone with a pregnant female would find out about that during their standard prenatal care for evaluation.
There is more pregnancy and whelping basics information and detailed links for you in the link if you are interested in learning more about breeding. The third link is the US breed parent club for more breed specific information and resources.
q3525724.html#a2810229 http://www.woodhavenlabs.com/breeding.html
http://www.bichon.org/
q1679449.html#a2947871
q2722771.html#a3046267
q5762034.html#a2906893
q3388198.html
http://www.wildheirlabradorrescue.org/readingroom/what-is-a-back-yard-breeder.php
http://members.tripod.com/antique_fcr/goodbreeder.html
http://www.wonderpuppy.net/1breeding.php
http://www.petfinder.com/index.html
There is more pregnancy and whelping basics information and detailed links for you in the link if you are interested in learning more about breeding. The third link is the US breed parent club for more breed specific information and resources.
q3525724.html#a2810229 http://www.woodhavenlabs.com/breeding.html
http://www.bichon.org/
q1679449.html#a2947871
q2722771.html#a3046267
q5762034.html#a2906893
q3388198.html
http://www.wildheirlabradorrescue.org/readingroom/what-is-a-back-yard-breeder.php
http://members.tripod.com/antique_fcr/goodbreeder.html
http://www.wonderpuppy.net/1breeding.php
http://www.petfinder.com/index.html