March should be lovely. The water temperature might be a bit cool for the locals, but coming from the UK it should feel lovely. It's 20C today just north of Dubai. I've seen thick jackets and wolly hats being worn. I'm still in linen trousers and s teeshirt!
I went in February and it was hot! It’s a fab place and the medical facilities are great, just check your insurance covers both you and potentially a premature baby (depending on how pregnant you will be!). I went when pregnant and had a great time (although camping in the desert was probably ill advised!!)
We did get some late rain this year. And the temperatures didn't pick up til later than normal. But I suspect it rains less than a dozen days a year. Maybe only half a dozen.
Just to put it in perspective, DS2 is wearing shorts, and I'm in a teeshirt today. People were sunbathing at the pool today (think i was the last one swimming 2 weeks ago in an unheated pool tho) Our A.C. still kicks in to keep the house below 25C. March will be warmer.
They have been attempting to encourage potential clouds to drop rain for a couple of years. So uf therd are clouds (rare) they seed to try and make the rain fall over the land rather than the sea. I'm a bit further north. March was unseasonably cold. The unreasonable rain could have been encouraged by the authorities. To put rain in perspective, I think we've had one day of threatened rain since Feb (when we got a deluge) or maybe March. They are desperare for rain atm.