Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- There is nothing wrong in having intercourse with a pregnant wife unless that will harm her or the baby.
2- The principle of honorable cohabitation implies that one should not force one’s wife to do anything painful or difficult.
In his response to your question, Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states,
There is no taboo against sexual intercourse during pregnancy unless the couple has been advised against it by their medical practitioner or obstetrician because of some special circumstances.
We find nothing in the authentic sources of Islam, such as the Qur’an, Hadith or fiqh, that either explicitly states or implicitly suggests otherwise. It is also common knowledge that sexual intercourse during pregnancy poses no health risk either for the fetus or the mother in normal cases.
Therefore, the general Islamic rule of permission prevails in this case unless the husband and wife are advised by the physician or midwife because of special circumstances.
It is, however, advisable for the couple who are engaging in sexual intercourse during pregnancy to exercise caution and avoid positions or methods of intercourse that may likely prove harmful.
Allah Almighty knows best.
Excerpted, with slight modifications, from: www.islam.ca