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May a pregnant woman visit a cemetery?
From the letter of the law, it is permitted for a pregnant woman to enter a cemetery. However, many women are accustomed not to visit a cemetery when they are pregnant. Those that have received such a custom are to abide by it. However, it is permitted for them to visit the grave of a Tzaddik or the grave of a loved one on the day of the Yartzite and the like. Many women are lenient in all cases, as is the letter of the law.
 Minchas Yitzchak 10:42; Nitei Gavriel Aveilus 2:84-4
 Pashut as there is no source for forbidding it, and so is proved from the fact the Poskim [below] bring that even the wife of a Kohen that is pregnant may enter a cemetery, and as writes the Kneses Hagedola [brought in Birkeiy Yosef 343/4] that even by the pregnant wife of a Kohen those who are stringent are doing Minhag Borus [custom of ignorance], hence certainly the wife of a Yisrael is allowed.
 This custom has no known source. A number of possible reasons are suggested: 1) Perhaps this is due to the fact that it is proper for the pregnant wife of a Kohen to avoid a cemetery, and hence we see that the fetus can receive impurity. Now since we await the rebuilding of the Temple every day the women avoid going to a cemetery, as if the Temple is rebuilt while they are still pregnant they will be able to give over their pure sons to perform the necessary actions required for the Para Aduma. [Minchas Yitzchak ibid; See Parah Mishneh 3/2] 2) Alternatively, it is because they desire to avoid any impurity during the pregnancy. [Nitei Gavriel ibid; See Sheivet Hamussar 24]
 Poskim ibid based on Rashba that we do not differ a tradition received from righteous women even if we have 600,000 proofs against it. [brought in Heishiv Moshe 13]
 Nitei Gavriel ibid
 Heard from Rav Asher Lemel HaCohen