Among the reasons accepted by the Sharih as valid for practising reversible contraception are:
(A) Physical weakness.
(C) The wife maintaining her beauty or figure for the sake of her husband.
(D) The couple being on a journey or in a distant land.
(E) Adverse political conditions, e.g. children are forcibly separated from their parents as is advocated by communism; etc.
(F) The couple decide to separate in the near future.
(G) The wife is an immoral person.
There are valid grounds for practising reversible contraception. Poverty or the fear of poverty are not valid reasons for contraception. It is not permissible to practice contraception on account of a fear of not being able to provide for a large family. Such a fear is an attribute of non-Muslims. According to the Quran Shareef: 'There is not a living creature, but its sustenance is the responsibility of Allah.'
Similarly desire to curb sexual desire which may stem out of piety is not a lawful ground for contraception. If practised for any reason which is unlawful in Islam, then contraception will likewise be unlawful, e.g. for indulgence in illicit sex.
[Note: For related opinions search the keyword: contraception.]