I did a bit of search, didn't really come up with much either, there are a few graphs on the site where I found this... if you want the link, let me know and I'll pm it to you...

Measurement of hCG is a diagnostic test for pregnancy and
can be used with progesterone to monitor early pregnancy
status. Estriol is an estrogen produced exclusively by the
fetoplacental unit and can be used to determine fetoplacental
distress in third trimester pregnancies. The roles of PAPP-A
and Inhibin A in pregnancy continue to be investigated.
Pregnancy
Best thing would probably be to ask your doc, he should be able to explain everything to you...