Wow, what a rollercoaster!
There is a study called HYPITAT that says that after 37 weeks, there's more risk than benefit to expectant management, even if your preeclampsia is mild. The study came out a couple of years ago and OBs have been incorporating it into practice, but not all do. That's why you're hearing 2 different possible scenarios.
It's really not easy to predict progression--your blood pressure is quite high though (labetalol doesn't treat the underlying problem--it temporarily lowers your BP, lowering your risk of seizure and hopefully keeping a good blood flow to the baby). Estimates about a week, three weeks, 37 weeks--they're educated guesses based on experience. These kinds of guesses aren't bad--they just have limitations. That's why we keep monitoring because preeclampsia is not predictable.
Aliza - 01/05/2007 - Severe preeclampsia, emergency CS 37 weeks
Isaac - 09/26/2011 - controlled on 150mg Toprol, NO PE, 39 weeks!