The cervical os has several shapes.

Nov 15, 2025 Source: Cainiu Health

Dr. Zhang Lu

Introduction

The cervical os primarily has two basic shapes: circular and transversely slit-like. Differences in shape are often related to whether a woman has experienced childbirth; the circular type is more common in women who have not given birth, while the transversely slit-like shape is more prevalent among parous women. Both shapes are considered normal physiological variations and do not require special treatment. Regardless of the shape of the cervical os, women should pay attention to cervical health and undergo regular gynecological examinations.

The cervical os primarily has two basic shapes: circular and transversely slit-like. Differences in shape are often related to whether a woman has experienced childbirth; it is usually circular in women who have not given birth and transversely slit-shaped in those who have. Both shapes are considered normal physiological variations and require no special treatment. Detailed explanations are as follows:

In women who have not undergone vaginal delivery, the cervical os is typically circular with smooth, regular edges. This is because the mucosa and muscular tissues of the cervix remain intact, and the external cervical os has not been stretched during childbirth, thus maintaining its natural anatomical form. This circular shape allows for better closure of the cervical canal, reducing the risk of pathogen invasion into the uterine cavity and offering some protection for reproductive health.

In women who have experienced vaginal delivery, the cervical os often becomes a single horizontal slit. During childbirth, passage of the fetus causes significant dilation of the external cervical os, leading to tearing and remodeling of the cervical mucosa and muscle tissue. After delivery, the cervical os cannot fully return to its original circular shape, resulting in a transversely slit appearance.

Regardless of the shape of the cervical os, women should pay attention to cervical health. Regular gynecological examinations, including cervical cytology (Pap smear) and HPV testing, can help detect cervical abnormalities early.

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What are the symptoms of cervical polyps?

In general, cervical os polyps refer to cervical polyps. Cervical polyps are localized benign growths resulting from hyperplasia of cervical tissue, which may be caused by chronic inflammation, cervical infection, or other factors. The main symptoms of cervical polyps include abnormal vaginal bleeding, abnormal vaginal discharge, pain, dysmenorrhea, and infertility. Due to the variety of symptoms associated with cervical polyps, patients should seek timely medical attention and undergo gynecological examination.

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What causes slight bleeding in the third trimester of pregnancy without abdominal pain, and what should be done?

In late pregnancy, slight bleeding without abdominal pain may be caused by factors such as bloody show, cervical polyps, placenta previa, early placental abruption, or vaginitis. Symptoms can be managed through symptom observation, bed rest, medication, and medical monitoring. If bleeding increases or abdominal pain occurs, immediate medical attention is required. In late pregnancy, the cervix matures, and the fetal membranes near the internal cervical os may separate from the uterine wall.

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What should I do if the placenta is close to the internal cervical os?

When the placenta is close to the internal cervical os, measures such as regular prenatal checkups, reduced physical activity, avoiding uterine stimulation, preventing bleeding and infection, and adjusting the delivery plan should be taken. In most cases, the condition gradually improves as gestational age increases, so excessive anxiety is unnecessary. If symptoms such as painless vaginal bleeding or abdominal pain occur, prompt medical attention is recommended. Ultrasound examinations should be performed every 4 weeks during the second trimester and every 2 weeks during the third trimester.

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Is it normal for the placenta to be 3 cm from the cervical opening?

If the gestational age is less than 28 weeks at the time of examination, the lower uterine segment has not fully formed and the placenta may appear relatively low, with a distance of 3 cm from the internal cervical os, which is a common presentation of placenta previa. As gestational age increases, the uterine body gradually enlarges and pulls upward, causing the placenta to typically migrate upwards as well. By 28 weeks of gestation or later, the placenta may return to a normal position. In such cases, there is no need for excessive concern; regular follow-up examinations are sufficient.