If there were any pregnancy complications a GP would surely confirm the need for time off work?
Not necessarily. Not all GP's are good. Not all GP's accept pregnancy issues.
I had chronic sickness with my first, an entire month of permanent migraines, and then severe SPD. My colleagues were bitches. Called me precious, said I was being OTT with symptoms etc. My GP didn't help.
Second pregnancy, self employed. HG diagnosed, severe again, SPD worse, migraines worse.
Third pregnancy now. All of the above again, luckily self employed still. Thank god I don't work with any of those judgmental types any more 
Also, had chronic endometriosis before pregnancies, and had to have time off during periods (2 days a month) and again, bitchy colleagues judged and hated me because their periods weren't that bad so therefore mine shouldn't have been. GP was useless then as well.
Try not to judge others. Carrying a baby is incredibly special, and also difficult for those who have had previous miscarriages. It may make them seem precious, when all they're doing is trying to keep their precious baby safe.