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 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.