Carbon dioxide is a pure substance. A pure substance can be an element or a compound. Carbon dioxide is a pure compound, consisting of two kinds of atoms that are bonded together. An element consists of merely one kind of atom. For example, oxygen is an element.
For Downâs syndrome, a blood test called the quadruple test is available from weeks 14-20 of pregnancy. For Patauâs and Edwardsâ syndromes, you will be offered a mid-pregnancy scan that checks for physical abnormalities.
Cramping During Pregnancy. It can be frightening to experience cramping during pregnancy, but our guide will let you know what's normal, what's not, and how to tell the difference. Cramping is a common -- but often scary -- symptom of pregnancy.