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A pregnant woman needs to visit a doctor regularly in order to detect any deviation from the norm in time. One of the important indicators that you need to monitor directly before the day of birth is the length of the cervix.
How is the norm of the length of the cervix checked and why is it needed?
The cervix performs its function while the woman is carrying the baby under her heart and during the birth process. This is an internal organ, it consists of muscles and ends with a pharynx. In girls who have not yet given birth, the pharynx will close, and in those who have already given birth, a slight opening of the pharynx is allowed. A healthy cervix remains long and elastic until delivery. It keeps the baby in the womb. Before childbirth, this organ becomes softer, and the pharynx gradually opens up to 10 cm. This is a sign that it is time for the baby to see the world.
From the 10th week until the very birth, the length of the cervix should be monitored. On each trip to a consultation with a gynecologist, a woman should undergo a detailed examination. There are 2 ways to check the length of this organ.
In addition to the length, during the examination, the maturity of the cervix is determined. It can be of 3 types: immature, ripening and mature
Manual inspection is carried out on the examination chair. The specialist examines the length of the neck, its density and the condition of the pharynx. In a healthy woman, the conclusion looks like this: “the length of the cervix is such and such, the structure is dense, the pharynx is closed.” For women who have given birth before, the wording “passes the tip of the finger” is allowed.
The second method of measurement is carried out using ultrasound with a transvaginal probe. This is the most accurate method, since the uzist during the examination can establish the length of the neck up to millimeters. Until the 20th week of pregnancy, such an accurate measurement does not make sense, since at this time the cervix is constantly changing. It is necessary to conduct at least one transvaginal ultrasound after the 20th week of pregnancy to exclude deviations from the normal state.
The length of the cervix during pregnancy by weeks
Small differences in the length of the cervix are acceptable in women who give birth for the first time and those who are expecting a second or more child. Let’s take a look at the average:
- 10-14th week – 35,4 mm.
- 15-19th week – 36,2 mm.
- 20-24th week – 40,3 mm.
- 25-29th week – 41 mm.
- 30-34th week – 36,4 mm.
- 35-40th week – 28,6 mm.
An insignificant error from 3,7 to 5,3 is permissible, depending on the duration of pregnancy.
Even if your cervix is not normal length, don’t panic. Listen carefully to your doctor, he will probably explain to you what is the way out of this situation.
Cervicometry during pregnancy – what is it
Cervicometry is a transvaginal ultrasound technique that measures the length of the cervix. When the cervix is too short, there is an increased risk of preterm labor. How cervicometry is done and in what cases the study is indicated will be discussed below.
Norms of the length of the cervix by week of pregnancy
Cervicometry during pregnancy – what is it? This is the most reliable way to measure the length of the closed part of the cervix. The transvaginal ultrasound technique is superior in accuracy to the transabdominal method for determining the length of the cervix. Cervicometry is performed for all pregnant women, but for women who have had a history of preterm birth, the results of the study are especially important. These patients are shown cervicometry every 15 days in the interval from 14 to 24 weeks of pregnancy. For other pregnant women, a single examination at 20-24 weeks is recommended. The procedure is absolutely safe for the mother and fetus and is practically no different from a standard ultrasound examination.
Norms of the length of the cervix by week of pregnancy:
- 16-20 weeks: 40-45 mm;
- 25-28 weeks: 35-40 mm;
- 32-36 weeks: 30-35 mm.
If the length of the cervix is 30 mm or more, the probability of preterm birth does not exceed the general population indicator. What length of the cervix indicates a high risk of preterm birth? If a shortened cervix (less than 15 mm) is detected, urgent hospitalization and a set of measures to prevent preterm birth (cervical cerclage, progesterone administration) are indicated. If, according to the results of cervicometry, the length of the cervix is less than 25 mm, then the patient is given a conclusion “ECHO-signs of CCI” with a recommendation to consult an obstetrician-gynecologist.
Cervicometry: preparation and technique
Before the study, you should empty your bladder. Cervicometry is performed in the lithotomy position (the woman lies on her back with bent knees). The doctor gently inserts the ultrasound probe into the vagina towards the anterior fornix. In this case, a sagittal view of the organ is obtained. The mucosa of the endocervix serves as a reference point for determining the position of the internal os. The doctor measures the closed part of the cervix, starting from the external os and up to the V-shaped notch of the internal os. This concludes the study and the patient is given a conclusion.
Transvaginal cervicometry can detect a number of important clinical conditions that range from preterm labor to polyhydramnios (polyhydramnios). Detection of a short cervix by transvaginal ultrasound at 18–24 weeks of gestation is the most important predictor of spontaneous preterm birth. If the length of the cervix at 14–24 weeks of gestation is less than 15 mm, then with a probability of 50%, preterm birth may occur at a gestational age of up to 33 weeks. In women with a previous unfavorable anamnesis, a pattern can be traced: the shorter the cervix, the more likely recurrent preterm birth, and with a length of less than 10 mm, the probability increases to 90%. That is why it is so important during pregnancy to be observed by a gynecologist and timely conduct transvaginal cervicometry.