From BA.com
"In order to qualify for the maternity/paternity/adoption leave freeze, members will need to provide a letter from their doctor, a birth certificate or documentation relating to the adoption or paternity leave and email it to
[email protected], along with their Executive Club membership name and number.
Children enrolled in a household account can accumulate Avios points for flights, however only adults aged 18 years or over in the household account can redeem points.
The maternity/paternity/adoption leave freeze offer is available to both biological and adoptive parents and members’ status will be extended for a further year.
Members who have received complimentary status or have Gold or Gold Guest List membership for life are not eligible for the maternity/paternity/adoption leave freeze.
Eligible Members are limited to a maximum of two approved applications for the maternity/paternity/adoption leave freeze within a five year period.
The maternity/paternity/adoption leave and seat selection on short-haul basic are available to Executive Club Members around the world."