My wife and I are going through our second pregnancy and your situation sounds very similar to our first except you are already past 37 and in full term land. Our daughter was induced at 35 3/7. Five days prior to that my wife's BP shot up from 105-110/65-70 to 130's/high 80's. We had just done a 24 hour with negative protein (like as in 0-5 low) she was not swollen (edema), no pain, no headache, baby was a bit small, but was tracking the same growth patter she had for the entire pregnancy. All good. Over the next four days BP up but would go down when she rested, 24 hour came back in the mid 300's, she gained about 6 pounds, and when they did another ultrasound amniotic fluid was ok but she had not grown at all. They induced immediately, and by the time she was born my wife protein was really high and the delivery was rough because they lost the fetal heart rate and had to attach the internal one. It all turned out fine and Isabel spent all of twenty minutes in the NICU, but it progressed really fast. Currently, she is 37 3/7 with our son and just has high BP. I don't want to scare anyone, but PE is spooky. I would suggest that you demand (in a kind forceful tone) that they measure Gavin's size. I would recommend that if he is falling off at all from his growth pattern, you may want to induce now when you can be in the driver's seat as much as possible.
One other note, the measurement with the ultrasound are really not that reliable +/-3 weeks or so, but if you wife has high BP 400 protein and edema, I think the +/-3 weeks becomes less speculative and more of an indicator that you need to seriously consider taking action. The other's on this forum may correct me if I am wrong, as I am not a medical doctor, but this was our experience,so I hope it helps.
On another note, have they said that your wife will have magnesium IV during labor. It is usually standard to reduce the chances of seizures from PE. My wife, and I kid you not, still says to this day that the IV's were worse than the delivery. She was truly miserable. By the way hand massages and foot massages did wonders and still do to help my wife relax.
We are going in to the Doctor's tomorrow and even though my wife's BP was 114/80 tonight, I can almost guarentee you that she will have a high reading tomorrow and we will be at Labor and delivery tomorrow afternoon. Best of luck to you adn your wife and son.
Ohh yeah, ask the doctor's to explain the delivery room team and procedure, because it can be pretty weird if the NICU people come in probably 3 or 4 people you may not have ever seen before and they wisk in with a crazy array of equipment, poke and prod etc. They are great but it can be pretty fast paced. Also talk with your wife about what you should do if, and I emphasize a BIG IF because you are past 37 weeks, but if they have to take Gavin out of the room for observation, does she want you to go with Gavin stay with her, etc. Regardless, have a camera when you go or stay, That first family photo on Mom's chest is a great bonding moment, but it screams by. Try to stay as calm as you can and ask them to explain the monitor so you can help your wife as she goes through contractions. Tell her the Fetal heart rate, distance between contractions, severity of contractions. I stared at the monitor for almost 20 hours and started to see patterns that when I told her the patterns helped her relax.