Meet the Clydesdale. The Clydesdale breed once almost faced extinction. Even though there is little practical use for heavy horses today because their muscle power has been replaced by machinery, breeders and enthusiasts have ensured that the breed is increasing, rather diminishing in numbers.
1 Over the three decades, the twin birth rate rose by 76 percent, from 18.9 to 33.2 per 1,000 births (or from 1.9 percent to 3.3 percent of all births) (Figure 1). 2  Increases in the twin birth rate averaged more than 2 percent a year from 1980 through 2004 (peaking at more than 4 percent from 1995 to 1998).
1 In a twin pregnancy. the average is 37 weeks. for triplets 34 and quadruplets 32 weeks.  The average birth weight for singletons is 7 lbs 7 oz. Average birth weight of twins is 5 lbs 5 oz. for triplets 4lbs and quads 3lbs. A difference in birth weight between multiples is not unusual.