Is it permissible to take birth control pills or use rubber contraceptives to postpone pregnancy for a certain period, or are there other methods for postponing pregnancy?

If there is a benefit in delaying pregnancy, then there is no harm in that. One should resort to the easiest and least harmful means, and consult a specialized physician. Methods for delaying pregnancy include: condoms, pills, injections, and IUDs. The ruling on these things varies according to the risks, harms, and Sharia (definition) prohibitions associated with them. Perhaps the safest method, free from these harms and prohibitions, is: regulating sexual encounters between the spouses, by the husband avoiding intercourse during the fertile period, which is the middle ten days of the menstrual cycle.