Pregnancy is essentially a well-tolerated subacute parasitosis. Oh's Manual (7th ed) has an excellent little table on page 685, which summarises the changes in physiological variables during pregnancy. This table is essential, and should be committed to memory.
Summaries and discussions of pregnancy-related problems from Life in the Fast Lane are made available as a list of links in the Resources section.
Pregnancy, Obstetrics and Gynaecology