The process of giving birth is accompanied with feelings of anxiety, stress, anticipation, and uncertainty; nonetheless, motherhood is a joyful experience overall, and the delight of meeting one's new baby comes hand in hand with these feelings (Bahn, 1998). Every woman's labor progresses in her own individual manner, with each stage presenting a new set of challenges for the lady to face, as well as questions and concerns for the woman's relatives and the obstetrician to ponder (Bartha et al., 2005). One of the most difficult questions for an expecting mother, her family, and the treating physician to answer is when labor pains will begin following an induction of labor, how they will correlate with cervical dilation, and whether or not a vaginal birth will occur as a result. Predicting when labor pains will begin after induction is one of the most difficult things to do (Chandra et al., 2001).
1.2. Anatomy
The cervix is a tube that is hollow and stretches into the vagina to produce fornices. This process takes place throughout pregnancy (Rozenberg et al., 2005). It measures between two and three centimeters in length (12) and has two sets of minute openings on either end. These openings, known as the internal and external ora, are connected by the endocervical canal (Suganthi & Sathiaseelan, 2023). It is composed of two pieces, one that is located above the vaginal opening and one that is located below it (both of which are technically the portio vaginalis). The peritoneum encircles the supravaginal region and surrounds it from behind. Women who have had several children have a longitudinal slit rather than the circular external os that nulliparous women have. When speaking of the uterus, the term “flexion” refers to the angle produced between the long axis of the corpus and the cervix, whereas the term “version” refers to the angle formed by the uterus's junction with the upper vagina. Both terms are used interchangeably. The lining of the endocervix is made up of columnar epithelium, while the lining of the ectocervix is made up of stratified squamous epithelium (Cirillo et al., 2023). The lower uterine segment at term develops from the isthmus, which is the area between the anatomical internal os and the histological internal os. Because of this, the lower uterine segment at term has a special relevance in obstetrics (Chandra, 2001).
In the cervix, the smooth muscles, fibroblasts, and blood vessels are embedded in an extracellular matrix made up of collagen (type I (70%) and type III (30%)), elastin, and proteoglycans. The tensile strength of collagen is best preserved in fibers longer than 20 meters in length (Pandit 2023). The structure of collagen is a triple helix (Anand et al., 2023). It may form fibers, bundles, and fibrils by cross-linking. The human cervix contains the tiny molecular-weight proteoglycan decorin, which plays a role in the formation of collagen (Vashishtha & Dhawan, 2023). During pregnancy, cervical cells create a substance called decorin. There is a disorder of the collagen fibers as the decorin to collagen ratio rises, since this leads to a scattering of the collagen fibrils (Vashishtha et al., 2020). Collagenases break down collagen to gradually weaken the collagen matrix and permit cervical dilatation during a medical abortion (Verhoeven et al., 2012).
Bands of elastin, 20-30 m in thickness, run parallel to the collagen fibers. They are incredibly elastic, and under mechanical stress, the cervix may dilate to double its normal size.
Along its length, the cervix varies in the proportion of connective tissue to smooth muscle. Connective tissue makes up a larger percentage of the distal section than smooth muscle does in the upper cervical region near the myometrium.
The cervix is made up of smooth muscle cells and fibroblasts. The cervix becomes hyperplastic, or thickened, due to the proliferation of smooth muscle cells and fibroblasts in early pregnancy. Normal cell death (apoptosis) happens later in pregnancy. Further cell growth is inhibited by decorin, and it also aids in the dispersion of collagen fibers. The cervix becomes more distensible because water is drawn in as a result of the collagen's disarray.