All Muslim wives are required to assist their husbands and to observe their marital duties towards them as best as they can regardless of whether they are pregnant or not. There is nothing in Islam that restricts the activities of the pregnant wife just because she is pregnant or because of some common superstitions.
Of course, Islam is the religion of mercy, and the husband should assist his wife in doing the household chores especially when she is pregnant and in need of help. But to say that the pregnant woman should not venture out in the open or should not do the household work merely because she is pregnant is totally baseless and lacks proper evidence from the Qur’an and the Sunnah.
However, if for a medical reason the doctor or healthcare giver states that a pregnant woman should refrain from walking or standing too much or from doing certain heavy duties, then the husband should help his wife more and she should limit her activity. With this, he will be applying the teachings of Islam, which encourages husbands to treat their wives kindly. In this case, he will be interpreting the real meaning of love and mercy clarified in the following Qur’anic verse: (And of His signs is this: He created for you helpmeets from yourselves that ye might find rest in them, and He ordained between you love and mercy. Lo, herein indeed are portents for folk who reflect.) (Ar-Rum 30: 21)