Hi Meg! Boy, I'm sure a whole bunch of us (incluiding myself!) can identify with your sister's worry!
There IS hope! I don't know if your sister's doctor mentioned it, but often when women develop hypertension before or near 20 weeks, it's not necessarily considered PIH, it's considered as being caused by underlying chronic hypertension. What's so good about that? Well, women with chronic hypertension are considered to have a 25% chance of developing superimposed preeclampsia. Women who have chronic hypertension that's easily controlled are considered to have chances of a good outcome close to 'normal' women. [:)]
I know she's on meds, but remember, these meds aren't the most effective meds out there- or else they'd be used frequently in a context outside of pregancy. They are, however, the meds considered the safest for her baby. Your sister may need an increased dose to bring her pressures down, or to try a different med. In any event, don't panic yet!
Hypertension is rough on babies, there's no doubt about it- it can cause smaller babies, placental abruptions, low amniotic fluid, etc. but just having hypertension doesn't make it automatically happen, and it's encouraging that her docs are treating it so readily.
But, just to answer your questions- the recurrence statistics range from 20-60% with the most common number thrown out there being 33%. Anne has mentioned often that 50% of gestational hypertension (or PIH) turns into full blown PE. And, really, there's no way of knowing if PE does turn up, if and when it will get severe.
Some people may disagree with me- but the most current research indicates that strict bedrest probably has little effect on outcomes. Doctors prescribe it because it can't hurt (they think) and could potentially help. They don't realize, however, how much guilt many of us feel when we are unable to keep strict bedrest.
My doc and the peri I saw prescribed modified bedrest for hypertension (that began around 22 weeks, and ended with a PE free birth at 36 weeks) which included two uninterrupted four-hour blocks of time lying on the left side per day, to help encourage blood flow to the placenta.
I hope this helps some, and send your sister our best wishes for a healthy pregnancy and do let us know how she's doing!
Allicia 5-13-98 (35 weeks-pre-e)
Camille 4-17-03 (36 weeks- htn and oligo)