People in the organisation are cursed by their own GB. Following talks such as "Responsible childbearing in this time of the end" many delayed starting a family until later in life. As a result for some fertility levels were lower and it took longer to conceive. For others they were unaware that they had problems and so were too old to start IVF treatment.
Some older ones were so convinced that the end was near they decided not to have children and put all energy into the organisation. They are now pensioners with no one to leave their assets too, hoping for a new world in which they can start a family. The tragedy is that many are now dying and as resurrected ones they are not destined for family life.
People who are not Witnesses suffer infertility, miscarriges and birth defects so it is no surprise that the organisation suffers from these too. It is the pressure to remain childless which is the curse.