Stimulant use during pregnancy may cause which of the following in the infant?

A) low birth weight
B) increased heart rate
C) increased breathing rate
D) All of these.

Stimulant use during pregnancy can lead to low birth weight, as stimulants can decrease the blood flow to the fetus and limit its access to nutrients. Additionally, stimulants can increase the heart rate and breathing rate of both the mother and the fetus, potentially causing stress on the baby's developing cardiovascular system. Therefore, all of the options (A) low birth weight, (B) increased heart rate, and (C) increased breathing rate, are possible consequences of stimulant use during pregnancy.