Hellin's law

[ hĕlĭnz ]

n.

The principle that twins occur once in 89 births, triplets once in 892 births, and quadruplets once in 893 births.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.