Mandatory medical device diagnostics.
- Vaginal sonographic measurement (vaginal ultrasonography; ultrasound procedure in which the ultrasound probe is inserted vaginally) of cervical length (cervix length).
Vaginal palpation in to assess the cervix is a subjective, difficult to reproduce examination with many sources of error. It is possible to partially assess the position, consistency, width of the external cervix and possibly that of the cervical canal, but not the total length and the internal cervix. Vaginal sonographic assessment of the cervical situation is preferred today because both the cervical length and the internal cervix (possibly funneling) can be reproducibly determined.
Opening of the cervix begins physiologically, but also in cervical insufficiency, in the region of the internal cervix with a funnel-shaped opening that progresses slowly caudally, in combination with shortening of the cervix.
Cervical length shows considerable individual variation, both during normal pregnancy and in developing cervical insufficiency in asymptomatic women, in pregnant women with or without a distressing history (e.g., condition after preterm delivery or cervical insufficiency), and in symptomatic patients (contractions, preterm labor). For this reason, despite numerous studies, there are still no generally binding standard values and no cut-off value (tolerance limit) of the cervical length at which a preterm birth must be expected or at which therapeutic measures (e.g. cerclage) must be taken. It is therefore only possible to a very limited extent to predict at which value a shortened cervix with or without funnel formation is an indication of preterm birth.
Therefore, if insufficiency is suspected, follow-up values at 2-3 week intervals are useful. This is especially true for the high-risk population: status post cervical insufficiency, late abortion (miscarriage in the period from the 13th to the 24th week of gestation (SSW)), or preterm delivery. Routine sonographic cervical assessment as part of the ultrasound examinations in the 19th-22nd and 29th-32nd weeks of pregnancy, which are anchored in the maternity guidelines, is currently not discussed in Germany.
The following values are considered a rough guideline because of the wide range of variation:
- Up to 20 SSW, sonographic measurement is uncertain because the actual cervix cannot be reliably distinguished from the lower uterine segment.
- Until 30 SSW, the average cervix length remains about 35-40 mm.
- By 40 SSW, the average cervical length slowly shortens to about 30-35 mm
- Values ≥ 35 mm cervical length are considered largely unproblematic
- Values between 25 mm and 35 mm should be observed and checked at short intervals
- As a threshold for an intervention recommendation (cerclage / cervical wrap or surgical cervical closure, pessary insertion, intravaginal (“into the vagina”) progesterone application) is often considered a shortening of the cervix length to:
- ≤ 25 mm in pregnant women with a stressful history.
- ≤ 15 mm in pregnant women without stressful anamnesis.
