Final answer:
The percent of diagnosed pregnancies that end in miscarriage is 15-20%. This can be influenced by maternal age, with older mothers at a higher risk.
Step-by-step explanation:
The percent of all diagnosed pregnancies that end in miscarriage falls within the range of 15-20%. Miscarriage, also known as spontaneous abortion, refers to the loss of a fetus before the 20th week of pregnancy. This rate can be influenced by a number of factors, including maternal age, with older mothers having a higher risk of miscarriage. For instance, the incidence of having a fetus with trisomy 21, which is associated with Down syndrome, increases with maternal age.