As redcrx said the waters can break before labour but normally the baby will be closely monitored or induced because of the risk of infection.
If there is no water around the baby for long it can cause serious complications with development and often results in deformities of limbs and the baby is pretty much squashed in the uterus. They can also have problems with lung development as they "breathe" the fluid before birth and it can be a sign of genetic problems.
Some people say they have no fluid as an exageration of the babies size. Sometimes if you have a large bump people say "oh it's all baby", where as some people appear to have a lot of fluid. Either way most healthy pregnancies have roughly the same amount but you feel it differently depending on the babies possition.