Parsley is a common herbal addition to foods, and it generally seems to be safe for most people to eat. Scientists question the safety of very high amounts of parsley in pregnancy, however, as the herb contains oils that are known to have effects on the uterus. As of 2011, it is unknown what the safe limit of parsley is for pregnant women, although levels normally found in food appear to be safe.
Less than 1% of parsley leaf is the oil component, and it is the oil that contains the potentially dangerous substances to the pregnant woman. These substances, myristicin and apiol, are known to have biological effects; in high quantities, they can trigger contractions of the uterine muscle, which can theoretically produce premature labor and present a danger to both mother and child. Historically, the herb has been used to promote the onset of menstruation, which also involves uterine contractions.
Myristicin is also able to affect the baby, by traveling across the placenta and into the baby's body. Once the chemical has got into the baby's body, the substance can raise the rate at which the baby's heart beats. Parsley is available in various extract forms, such as the oil, the seeds and the juice, and these substances may be more risky than the natural leaf form.
Parsley in pregnancy can cause allergic reactions on rare occasions, especially if the woman is already sensitive to plants like carrots and fennel. Apart from the potential effects on the uterus, parsley oil extracts are also capable of producing issues like kidney damage or seizures as side effects. Herbal teas that contain parsley may also give the woman too high a dose of apiol and myristicin for safety. Another possible effect of parsley in pregnancy is that the woman can suffer from diuretic effects, which can result in the loss of more water during urination than normal.
Pregnant women should be aware than the recommendations for food avoidance are continually updated as more scientific research is published, and more is known about specific foods. Therefore, a woman should always ask a doctor about taking parsley in pregnancy, or any other foods or herbs, in case the recommendations have been changed. Foods like tabbouleh, which can often contain very high levels of parsley, may be unsuitable for eating during pregnancy, so a doctor's advice should be sought for these foods in particular.