I regularly check my weight to keep it in my comfortable healthy zone (and react promptly if it sneaks over). I was only weighed at the initial MW appointment both times.
My weight went from 9st 2, down to 8st 7 because I was struggling to put food in my mouth between months 2-4. Meanwhile I quickly ended up in maternity clothes from 8 weeks as I was clearly gaining bump. Then my appetite returned... by the end of pregnancy I was 13st. That was a gain of 50% of my body weight in less than 5 months.
It was clearly a huge bump. A large-for-me baby with a large amount of fluid. Some odema. I had two extra scans to monitor that all was OK. I had a fundus of 45cm when in early labour at 39 weeks. I looked like I had a swiss ball up my top.
I had about 2st of "me weight" to lose after which came off easily enough. I'm normally active and eat decently, but in the early months suffered from dementor like exhaustion and no energy from the nausea/ loss of appetite. SPD began to creep in before I was properly recovered from that. The last month I was trapped in the house unless I was ferried door to door and spent very long days trapped in the house alone unless I had visitors. I also had carpal tunnel syndrome which meant I was exhausted from waking hourly to reactivate dead limbs and heave my body over. My hands were numb. My brain had no attention span. All I was capable of doing was comfort eating (online shopping) and playing computer games. That last week, I was so heavy that I couldn't get off the sofa on my weakened legs unless there was someone in the house to drag me off.
I was determined to never be 13st again. In the second pregnancy I kept moving, finding a pair of crutches so that the water retention didn't build up. It also helped that my nausea was in a normal league so could keep my weight steady in the early months and managed to keep reasonably active through the first half until SPD gate crashed again. I then by-passed NHS protocol and borrowed some crutches from a friend to keep myself moving. I tried to resist sugar cravings near the end. I ended up at a much more comfortable, 12st. Still the same "me weight" to lose after. Much less water retention.
I wish I had support to keep active first time, not having SPD dismissed as pregnancy aches and pains when I was no longer able to do things like going around the supermarket. I was exhausted long before a 48hr labour/ EMCS. Being so weak and inactive could have been a factor in a badly positioned baby, and I was unable to postion myself well for birth. I do think my weight/ SPD contributed to a difficult birth, probably not entirely, but they certainly didn't help.
Being monitored by the MWs could help pick up on additional issues, but only truely useful if they take action to assist.