Is it a good idea to keep pet cats in the house where there is a pregnant lady?

Tweet

My son is a furry animal lover as well as his wife. They have kept or raised two white and gray cats, one male, the other female, for about half a year. The cats are very cute and gentle and we all like them. The problem is my daughter-in-law is pregnant for three months. People say that it is not a good idea to keep pet cats in the house. We have tried to ask them to send the cats away for someone else to keep them, but they seem unwilling to. They say that they have already had the cats vaccined and that it does not matter. By the way, both cats are living in a huge cage where they enjoy their own freedom and seem pleased there. Sometimes they take it out for a walk to the lake. So I am wondering whether you friends or mylotters encounter or have encountered the same case. Can you please tell me if it is ok in the case mentioned above? Thank you in advance for your response.