When does the cervix close during pregnancy?

The cervix plays a critical role during pregnancy, particularly in maintaining a safe environment for the developing fetus. After implantation, which occurs when the fertilized egg attaches to the uterine wall, hormonal changes take place that lead to the closure of the cervix. This closure is facilitated by the increased production of progesterone, a hormone that supports pregnancy. As the cervix closes, it forms a protective mucus plug that seals the cervical canal, preventing bacteria and other foreign substances from entering the uterus. This closing process helps to enhance the stability of the pregnancy and create a secure environment for the developing baby.

The other options do not accurately describe the timing of the cervix's closure in relation to pregnancy. Before ovulation and before fertilization pertain to the events that occur before pregnancy even begins. During childbirth, the cervix undergoes dilation, which is the opposite of closing, as it prepares for the delivery process. Thus, the closure of the cervix is specifically linked to the post-implantation phase of pregnancy, making it an essential aspect of maternal and fetal health.