Wow ditzzy, that's not a good reading, that must be a shock. Are you on aspirin? It might be worth it but I'm not sure if you can take it if you're close to birthing. Are you being monitored now? Over 140/90 you are supposed to be checked again after 4 hours, but over 150/100 you are supposed to go in, most likely for medication. Even with no other signs of PE.
Sorry if you know all this - it's just been drilled into me because I am at risk and wasn't given proper care with DC1. My BP went to 170/130 in delivery which caused considerable panic from the MWs. It was 'just' hypertension though, not PE, it is possible.
If you're being checked again on Fri I suggest no caffeine, no salt, have a decent meal before as it lowers your BP, and make sure you have had a wee. Also, get there early and sit quietly (lie on your left side if you can!) none of these would mask a serious problem but might help it come down a bit.
I was advised by various consultants that in pregnancy a manual BP should always be taken - the machines run high and apparently don't always adjust for extra blood volume in pg. certainly when I have been monitored or have seen my consultant, they have taken it manually.
I had a MW appt this week and my BP was at 123/62 - about 20 points lower than booking in! Either the aspirin is working or I am a medical marvel...