The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909), in Parashat Sav (Halacha 14; listen to audio recording for precise citation), addresses the case of a woman who, due to extenuating circumstances, is unable to immerse in a Mikveh on the night when she became eligible for immersion. If the woman cannot immerse on the night following the completion of the seven-day Shib’a Nekiyim period, she may immerse on whichever night this becomes possible, and no additional Bedikot (inspections) are required. So long as the woman performed the required Bedikot during the Shib’a Nekiyim, she does not have to perform any further inspections before immersing in a Mikveh. Even if she does not immerse for another several days, she does not need any additional Bedikot before immersing.
One example is a case where the husband had to make an emergency business trip on the final day of the Shib’a Nekiyim, and returns only ten days later. The woman would not immerse in the Mikveh until the husband returns, and she does not have to perform any Bedikot in the interim.
It should be noted, however, that even in such a case, the woman must immerse specifically at night, and not during the day. The requirement to immerse specifically at night applies regardless of when a woman immerses, even if she does not immerse immediately following the completion of the Shib’a Nekiyim.
Summary: If a woman is unable, for whatever reason, to immerse on the night following the Shib’a Nekiyim, and she can immerse only several night later, she does not have to perform additional Bedikot (inspections) in the interim. Assuming she properly performed the required Bedikot during the Shib’a Nekiyim, no further inspections are required. The immersion should be done specifically at night, even if it takes place several days after the completion of the Shib’a Nekiyim.
