click here says:
Exclusive Accommodation for Ladies, Sr. Citizen and Pregnant Women
i.An accommodation of six berths in sleeper class of all the trains is earmarked for exclusive use of lady passengers.
ii.In addition to this a combined quota of 2 lower berths is earmarked in sleeper class, AC 3-Tier and AC 2-Tier classes for Sr. Citizens, Female passengers 45 years of age and...
more... above traveling alone and pregnant women in all trains.
iii.Pregnant women will be required to submit a certificate of pregnancy certified by one registered Medical Practitioner at the time of booking against the quota.