In fact, the preservation of human species is unquestionably one of the primary objectives of marriage, and such thing requires continued reproduction. Accordingly, Islam encourages having children. However, it allows the Muslim to plan his family due to valid reasons and recognized necessities.
Among the valid reasons for birth planning are the fear that the new pregnancy or a new baby might harm a previous suckling child due to frequent pregnancy and the fear that the pregnancy or delivery might endanger the life or health of the mother. This means that Islam recommends working out a strategy to improve birth spacing in order to lengthen the time between births and improve the health of mothers and their babies.
Referring to the ideal period for birth spacing or having interval between births, Sheikh Yusuf Al-Qaradawi mentioned in his book The Lawful and the Prohibited in Islam that: “The ideal birth spacing is thirty months, or, if one wants to nurse the baby for two full years, then thirty-three months. Referring to this, Allah Almighty says: “Mothers shall suckle their children for two whole years; (that is) for those who wish to complete the suckling. The duty of feeding and clothing nursing mothers in a seemly manner is upon the father of the child. No one should be charged beyond his capacity. A mother should not be made to suffer because of her child, nor should he to whom the child is born (be made to suffer) because of his child. And on the (father’s) heir is incumbent the like of that (which was incumbent on the father). If they desire to wean the child by mutual consent and (after) consultation, it is no sin for them; and if ye wish to give your children out to nurse, it is no sin for you, provided that ye pay what is due from you in kindness. Observe your duty to Allah, and know that Allah is Seer of what ye do.” (Al-Baqarah: 233)
In this context, Sheikh Ja`far At-Talhawi, a prominent Al-Azhar scholar, adds the following:
“There is nothing wrong if the spouses plan their family by having intervals between the births for the following several reasons: (1) This enables the mother to have an adequate period for rest to recover and return her strength, and (2) enables the child to complete the period of suckling for two years. It is well-known that frequent pregnancies without considering this spacing affect both the mother and the infant. The Prophet (peace and blessings be upon him) said: “…gheelah (pregnancy during the period of breastfeeding) overtakes the rider and throws him from the horse.” (Reported by Abu Dawud, this means that the child who nurses from a pregnant mother will suffer from it in later life like a horseman who is thrown from his horse.)”