The classic Morocco group tour involves shared minibuses, fixed departure times, and a schedule optimised for the group rather than any individual. That is fine for most travellers. During pregnancy, the calculus shifts: you may need an unplanned bathroom stop, want to rest in the vehicle while others browse the souk, or need to cut a day short if you are tired. None of that is possible on a shared departure.
A private guided tour solves most of these problems straightforwardly. Your guide knows which restaurants are trustworthy (and will flag the raw salad), your vehicle has reliable air conditioning, and the route can be adjusted in real time — skipping the rough piste shortcut through the palmery, for example, in favour of the paved main road. If you have a specific medical concern mid-trip, a local guide with real contacts is worth more than a phone number on a travel insurance card.
There is also the mental-load element. Navigating Fes medina while pregnant and map-reading simultaneously is more taxing than it sounds. Having someone who genuinely knows the city, knows where to sit down in the shade, and knows the nearest decent pharmacy is a practical benefit rather than a luxury.