Last, cenain micro RNA species mediate vascular remodeling and uterine blood low early in placentation (Sama, 2015). In particular, members of the miR-1e7-92 clusrer and miR-34 are important in spiral artery remodeling and invasion. Abnormalities of micro-RNA function have been reported in preeclampsia, fetal-growth rescriction, and gestational diaberes.
As early as 1 momh after conception, the cervix begins to soften and gain bluish mnes. These result from increased vascularity and edema of the entire cervix, from changes in the collagen necwork, and from hypertrophy and hyperplasia of the cervical glands (Peralra, 2015; Srraach, 2005). Alrhough rhe cervix contains a small amollnt of smooth muscle, its major componenr is connective (issue. Rearrangemem of rhis collagen-rich tissue aids rhe cervix in retention of the pregnancy until term, in dilatation to aid delivery, and in posrpartum repair and reconstitution ro permir a subsequenr successful pregnancy (Myers, 2015). As derailed in Chapter 21 (p. 409), cervical ripening involves connective tissue remodeling (har lowers collagen and proreoglycan concentrations and raises warer comenr compared wirh rhe nonpregnanr cervix.
Cervical glands undergo marked proliferation, and by the end of pregnancy, they occupy up to one half of the entire cervical mass. This normal pregnancy-induced change promprs an extension, or eversion, of (he proliferating columnar endocervical glands onto the ecrocervical portio (rig. 4-1). This tissue appears red and velvety and bleeds even with minor trauma, such as with Pap tesring.
FIGURE 4-1 Cervical eversion of pregnancy as viewed through a colposcope. The eversion represents columnar epithelium on the portio of the cervix. (Used with permission from Dr. Claudia Werner.)
The endocervical mucosal cells produce copious amounts of tenacious mucus thar obstruct the cervical canal soon after conception (Bastholm, 2017). This mucus is rich in immunoglobulins and cytokines and may acr as an immunological barrier to prorec( the uterine conrents against infection (Hansen, 2014; Wang, 2014). Ar labor onser, if not before, this mucus plug is expelled, resulting in a bloody show. Moreover, the cervical mucus consistency changes during pregnancy. Speciically, in most pregnant women, as a result of progesterone, when cervical mucus is spread and dried on a glass slide, it shows poor crysrallization, termed beading. In some gravidas, as a resulr of amnionic Auid leakage. an arborization of ice-like crystals, calledening, is seen microscopically.
HistOlogically, basal cells near rhe squamocolumnar junction can be prominenr in size, shape, and staining quality in pregnancy. 111ese changes are considered ro be estrogen induced. In addition, pregnancy is associated with bO[h endoccrvical gland hyperplasia and hypersecretory appearance-the Arias-Stela raction-which can make diferenriating these from truly atypical glandular cells during Pap test evaluarion particularly diiculr (Rosai, 2015).