Eating expired olive oil once, if there is no discomfort, generally will not affect the fetus. After eating expired olive oil once, the amount of oil consumed is not much, and after metabolized by the human body, the amount absorbed by the fetus through the placenta is minimal, and generally will not affect the normal development of the fetus in the womb. After eating once expired olive oil to observe the changes in the body, some pregnant women may experience nausea, vomiting, abdominal pain, diarrhea, the symptoms are serious, timely medical treatment, if there is a serious abnormality, may affect the fetus. The food you choose during pregnancy should be hygienic and safe in the first place. Foods that may spoil should not be eaten, and consuming them will be detrimental to the pregnant woman and the fetus. It is recommended to seek timely medical attention for any discomfort that occurs during pregnancy and treat it under the guidance of a doctor.