Pregnant women may defer Hac without sin if pregnancy poses health risks; those who choose to go should get medical clearance, stay hydrated, and take extra precautions against heat and crowds.
Islamically, Hac is farz only for those who are physically able (istitaa). If pregnancy poses a genuine health risk — due to complications, high-risk pregnancy, advanced gestational age, or the extreme physical demands and heat of Hac — the obligation is deferred until the woman is able. There is no sin in postponing Hac due to pregnancy. Most scholars advise caution, especially for first-time pregnancies or pregnancies beyond the first trimester during Hac season.
If a pregnant woman in good health and with medical clearance chooses to perform Hac, she should: obtain thorough pre-travel consultation with her obstetrician, carry complete medical records including blood type and pregnancy details, bring all prenatal medications and vitamins, stay aggressively hydrated (pregnancy increases fluid needs significantly), and avoid the most crowded situations (use wheelchair services, stone at off-peak hours, use upper floors for Tavaf).
The extreme heat during Hac season (often 45-50°C), extensive walking (50-70 km over several days), crowding, and physical exertion create real risks for pregnant women including: dehydration, heat exhaustion, falls in crowds, pre-term labor from stress and exertion, and limited access to obstetric acil durum care. Saudi Arabia provides extensive medical facilities during Hac, but access can be delayed during peak times. Most medical professionals and scholars recommend postponing Hac to after delivery and recovery unless the pregnancy is early and uncomplicated.
Source: Ibn Qudamah, Al-Mughni, chapter on conditions of Hac obligation