Here's my guess (and of course no one can really know without looking at medical record!) of what really happened. I think this mom is confused about the procedures she had. In a woman who wishes to keep her fertility and has localized cervical cancer, a cone biopsy (kind of a of misnomer since a large chunk of cervix removed, not really a biopsy) can be performed. If you think of the cervix as the neck of the uterus, basically they remove the outer portion of the cervix in a cone shape, so a deeper, but narrower piece of the internal cervix is removed and a wider, shallower piece of the outer cervix. I've never heard of a procedure that removes "half" of the cervix, nor would removing half preserve cervical function. I'm guessing perhaps her margins still showed cancer or dysplasia and a second cone was then done, deeper than the first. The non-pregnant cervix is 4-5 cms long, and a cone specimen is usually like 2-3 cms long from the narrowest part to the outside, leaving some cervix behind. Frequently women who have had a previous cone biopsy have a cerclage in pregnancy (a stitch to hold the cervix shut) as they are at higher risk of earlier cervical incompetence. This is removed at 36-37 weeks, and many women labor fairly soon after - but many don't and go into labor on their own weeks later. I have seen women with previous cervical procedures have issues with scar tissue, though. Often, these women efface fully but don't dilate well, and sometimes you can manually break up the scar and that helps. The most amazing case of that I saw was a woman who was obviously in hard labor, but not dilating, and the doc used his finger to break some small adhesions he could feel stretching across her 1 cm dilated cervix that was 100% effaced. Immediately, she was 9 cms! She birthed her baby not long after.
Anyway, it is unlikely this woman has *no* cervix as there likely would be no way to retain a pregnancy and removing the whole cervix basically would mean taking off the whole bottom part of the uterus. Most likely she had a cone and has a shortened cervix and had the stitch to help her make it to term.
Here is a fairly good picture of a cone biopsy
(note I did not read the accompanying text so I don't know if it's any good - I was just looking for a picture!)