Sisymbrium or mustard seeds are a popular spice used in Asian cuisine. In certain parts of India, mustard is a staple spice used in all kinds of delicacies. For centuries, pregnant women in these countries have been eating mustard seeds without notable consequences.
However, certain sources deem mustard seeds unsafe for pregnant and breast-feeding women, excess of consumption of which, may lead to bleeding. So, it is recommended you consult with a doctor before you include these seeds in your regular diet.