The best way to understand phrases is to break down each word's meaning. Mortality is deaths. Child typically means under age 12 (in medicine regarding deaths). Reduce means to lessen or reduce. So "reduce child mortality" means to lessen or reduce deaths of children under 12 years of age.

The survival of people having relapsing polychondritis has improved enormously the last years. A study in 1998 showed a 10 year survival rate of 98%. (Source: http://www.relapsingpolychondritis.org/relapsing-polychondritis/)

they cry, shiver, and tuck their legs close to their bodies

Well it depends

There are lots of thing that could kill infants.

for example

people

animals

deadly plants

water that you can drown in

and lots more things can kill infants

The term 'mortality crossover' refers to the fact that minority group members show shorter life expectancies than whites until old age, and then in later old age this trend reverses and they show greater life expectancies than whites.

There are no accurate records, but some estimates of infant mortality rates are in the range of 30% from all causes, perhaps higher in times of war and famine, and certainly higher in disease epidemics. Another estimate is that 1/3 of all children died by the age of 5, which seems high except for the primitive state of medical care, and the known rate of neonatal and pediatric illnesses even today.

Latvia is the nation with the highest infant mortality rate in the developed world, with a rate of 6/1,000(deaths/live births) in 2006.

The United States, Slovakia, Hungary, Poland and Malta come in at 5/1,000.