During pregnancy, several changes occur in the cervix, the structure between the vagina and uterus. Every pregnancy is slightly different and women may experience these changes at different rates. In the cervix during pregnancy, a mucus plug will form as the cervix thickens, and towards the end of the pregnancy, the cervix will thin and dilate, allowing the mucous plug to fall out so the baby can be delivered. These changes occur in concert with a number of other physical changes associated with the pregnancy.
The first change seen in the cervix of a pregnant woman is thickening as the cervix begins producing more glandular cells. These cells exude mucus, forming the mucus plug that will keep the uterus securely sealed during the pregnancy. The thickness achieved will vary from patient to patient. The cervix can also appear red or inflamed during examinations, and sometimes some breakthrough bleeding or spotting will occur.
Towards the end of the pregnancy, the cervix will start preparing for delivery. The cervix during pregnancy needs to be thick to keep the uterus protected, but will start thinning in preparation for delivery. Eventually, the cervix will start dilating and the mucus plug will be lost. In some women, these changes can occur weeks before delivery. In others, they only start happening as labor begins. Looking at the cervix will not necessarily provide information about how close a woman is to delivery.
Blood flow to the cervix during pregnancy increases, accommodating an increased need for blood. A woman's circulatory system also routes more blood to the uterus to support the developing fetus and provide a source of nutrients and a pathway for expressed waste products. The physical changes associated with pregnancy are often caused by changes in hormone levels, which fluctuate during the pregnancy. The hormones act as signals to initiate various physical changes during the pregnancy and in the process of labor and delivery.
Women who are interested in observing changes in the cervix during pregnancy can ask their doctors to show them during prenatal appointments. The doctor can hold up a mirror to make the area visible and describe the observed changes. It is also possible to look at the cervix at home, a practice some women may already be familiar with from tracking the production of cervical mucus. Keeping track of mucus production is a tool used by some women who are trying to get pregnant, allowing them to pick the best time during ovulation to attempt to conceive.