Hi, Thanks for the query. Usually eating normal mushrooms may not have major effect on pregnancy. But toxic mushrooms and magic mushrooms containing psilocybin or psilocin have to be avoided during pregnancy. Because according to some studies these magic mushrooms can induce premature uterine contractions. Marijuna can lead to low birth weight of the babies, lower IQ, behavioral problems etc. So better to avoid during pregnancy. Intake of single dose may not lead to much problems. But better to follow with regular antenatal checkups and ultrasound examinations. Take care.