Rhine Valley while pregnant?

We love the Rhine valley. Very scenic, lots of castles. Some very nice old towns. I'd suggest taking boat trips up-river (it's slower that way). It's all level along the river. There are trains on both sides of the river, and boats going both ways. And a couple of ferries for crossing the Rhine.

Some nice towns are Rudesheim (fairly big, some uphill to the top of the town), Bacharach, Oberwesel, St. Goar, Boppard, Koblenz (where the Mosel River joins).

I personally like St. Goar. The Rhein Hotel is right on the river, as is another, I forget it's name.

You'll get a lot of suggestions here. It's a popular area to enjoy. There are a LOT of castles along the Rhine, others can tell you which are closer to the river and not such an uphill climb.

It sounds ok to me. I’ve enjoyed the Rhine without going anywhere near a bike. Take the cruise boats. A shame to miss the wine but not much worse to miss it in Germany than anywhere else. There are some hills such as going up to the castle at St. Goar, but not that bad and you will do fine, and you can avoid that altogether by just sticking to the town areas along the riverbank which are flat. Mainz and Koln are interesting cities at either end of the scenic Rhine and they are flat.

The Rhine towns themselves do not require much if any uphill/downhill walking because they are built on fairly narrow spits of mostly-flat land near the riverbanks. If you stay in town, and do your walks in town, you'll be just fine.

Boppard has a great chairlift ride - Ruedesheim and Koblenz have gondolas - and these devices will allow you to enjoy the views from the clifftops. The same is true over on the Mosel River in Cochem... nice chairlift there.

CASTLES: Burg Eltz, Marksburg (in Braubach,) Rheinfels (in St Goar) and Reichsburg (in Cochem) are the biggies. How to reach these castles??

Eltz: Train + bus + Castle shuttle
Marksburg: taxi from Braubach town center
Rheinfels: public bus or taxi from town
Reichsburg: public bus or taxi from town

The problem with all these castles may come once you are inside. Lots of steps. not sure how you'll deal with those. Reichsburg is probably the easiest of all to negotiate on foot. From the website:

"You have to climb stairs in the castle during the tour (30 steps up to the first floor, 15 steps down a narrow spiral staircase and 10 steps down a balustrade)."

BOPPARD is a near-ideal base town in several ways. There are dozens of good lodging and dining options there, many with riverfront views. It's the closest of the small west-bank towns to Koblenz and to the Mosel Valley. And unlike St Goar or the other towns, every hotel/apartment guest there receives a free VRM Guest Ticket which provides unlimited public transportation to all the nearby towns I have mentioned.

St Goar is also a good choice; though it's much smaller, with fewer options and a Guest Ticket only in a few establishments, it has a lovely setting and a good location for most outings.

If you go to Rüdesheim, you could visit Rhein Main Welt where everyone can do wine tasting and they have a number of non-alcoholic wines to taste.