All the meforshim brought in pischai tshuva say against the noda beyhuda it is impossible to reach the cervix with ones finger since the penis which is longer cannot reach there.
Looking on the internet it says that a woman can touch the cervix with her finger.
Alan Ross, United Kingdom
Your question is the matter of a dispute among the Poskim of our time. The Shulchan Aruch (YD 196) and Poskim stated that a woman must check herself "in nooks and crannies until the place where the Ever reaches." The Rema concurs but adds that if she checked but did not reach that spot, it is acceptable b'Di'eved.
Rabbi Dovid Morgenstern, a pupil of Rav Elyashiv zt'l, says that a woman may check even up to the cervix, but should not rub it as it can cause bleeding. Other Poskim maintain that the accepted practice was to turn the cloth around with her finger but not to try and reach the cervix. This is also the view of most of the pupils of Rav Elyashiv as well as almost all other Poskim, including Rav Wozner zt'l, that one must do what was accepted even if technically it is possible to check up to the cervix.
According to medical sources, it is also possible for the male Ever to reach the cervix. Thus, even the Shulchan Aruch could be understood in accordance with the more stringent approach of Rabbi Morgenstern, but as previously stated this is not the view of most Poskim.
Yoel Domb