EK employed it's first female pilot in 2006- She recently competed her Command upgrade on the 777. There is at least one other Lady Captain now, an I think it may be two.
I know of at least two Ladies who are here flying and are single Mothers.
No idea of total numbers, but my guess would be less than 100 out of the 2700 currently employed.
I don't think Maternity leave for Pilots has even been considered, but I guess they'll deal with it when it happens. The Cabin Crew get (I think) 6 weeks UNPAID Maternity leave, and I imagine Pilots would be similar.
No way would it be as generous as in Western countries, but neither can they afford to lose Pilots, so I'd be suprized if it wasn't accommodated.