Abu Sa’eed Khudri narrates that Beloved Prophet (Peace be upon Him) said, “When a believer desires a child in Heaven (Jannah), the Pregnancy, birth, and growth of the child [to the age of 33] will be take place instantly.
The scholars have differed on whether or not there will be childbirth in Heaven (Jannah). Ibn Katheer says, “Tawus, Mujfthid, and IbrahIm An-NakhaI’ hold the view that sexual intercourse will take place in Heaven (Jannah) without childbirth and this is correct. There will not be childbirth in Heaven (Jannah) because there will be no need for it. Childbirth is necessary in this world for the continuation of humanity, whereas in Heaven (Jannah) the objective is lasting pleasure. This is why there is no ejaculation of sperm during sexual intercourse in Heaven (Jannah) because it would end the pleasure. However, when the people of Jannat desire children, they will immediately receive children. This is because Allah Ta’la has said, “They will have in Jannah whatever they desire. In this way Do We reward the people who carry out Our commands and refrain from evil” (16:31)
Some of the scholars are of the view that if a person wishes to have a child in Paradise, Allah will fulfil that wish for him. They quoted as evidence for that the report narrated by at-Tirmidhi (2563) in his Sunan from Abu Sa‘eed al-Khudri (may Allah be pleased with him) who said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “If the believer wishes for a child in Paradise, the pregnancy, birth and growth will occur within an hour, as he wishes.” Classed as saheeh by al-Albaani in Saheeh al-Jaami‘, 6649