Have been looking into UK CAA regs and IF they apply to a foreign carrier with a UK base then the Airline in question falls foul of:-
1. The Air Navigation (Cosmic Radiation) Order 2000. No.1104 - "..Operators shall ensure exposure to the foetus will be as low as reasonably achievable and unlikely to exceed 1 milliSievert during the remainder of the pregnancy"
Estimates of polar LHR - LAX - LHR or LHR - HKG - LHR flight patterns are that this will be reached or exceeded in 4 complete trips.
2. The Civil Aviation (Working Time) Regulations 2004. No.756 - this basically states that upon recomendation from a medical practitioner that working nights (2am - 4.59am locally adjusted) could pose health risks then the operator should move the crew member to appropriate ground duties. (Interestingly and unrelated it restricts crew members to 900 flight hours in every rolling 12 months)
I guess this is why every UK operator grounds their pregnant Cabin Crew.
Ammunition being forward to my wife's Union Rep for a shot across the bows!