Okay- I'll admit I know nothing about breeding- but am pregnant myself.
I'm curious, do you get ultrasounds on your foals before they are born? Is it common to know if you are having a colt or filly before they are born? What tests are common while your mare is pregnant? How often does the vet see a pregnant mare? Any other comparisons to human pregnancies?
I usually do an ultrasound at 15 days - to confirm pregnancy and one at 30 days to confirm that there are not twins - that is all I do. If nothing is wrong, the vet comes along at 5, 7 and 9 months for pnuemabort shots and then again at 10 months to give vaccines.
I then just have the vet out when the foal is born.
I have my mares ultrasounded at day 15 -17 to check for preg/twins etc. If it is questionable (for whatever reason - a difficult mare to keep preg, or a question mark on the ultrasound for twins etc) I'll ultrasound again around day 30.
I DO have my vet come back out on most of my mares around day 60 to fetal sex and to check pregnancy. My vet was wanting to up his numbers and also get more experience for fetal sexing so we worked out a deal that he doesn't charge quiet as much for the 60 day check. (btw - his numbers are spot on and he is 100% correct so far on my foal's sexes).
As for other "similarities" with human pregnancies... I found it fascinating that my cousin who has been doing in vitro and AI herself, has went through almost identical treatments as my mares with P and E and oxytocin, frequent ultrasounds to check for follicules etc... (and yes I'm happy to report that she is 13 weeks in "foal" herself LOL).