I'm currently 27 weeks pregnant and have been off since Tuesday with SPD. I was diagnosed with this last Friday and am awaiting referral for physio and taking codeine in the meantime.
Some days I have good days in terms of the pain and other days the pain is awful, like it has been this week. On top of this, it seems my sickness has also returned 
Anyway, in my work contract it does say that I should get paid normal pay before SSP starts, at their discretion, if I comply with their reporting requirements etc (which I have done).
Early in my pregnancy I was off with a couple hospital stays and then suffered with "morning" sickness (that actually lasted all day)