Cervical incompetence refers to a painless spontaneous dilatation of the cervix, and is a common cause of 2nd trimester pregnancy failure. 1.5% of pregnancies.
Causes:
Idiopathic
Connective tissue disorders
Trauma / surgery
Recurrent miscarriage or termination
Diethylsilbestrol exposure / uterine abnormalities
Presents with pregnancy loss or premature rupture of membranes with oligohydramnios
Fetal fibronectin can rule out premature labour, needs to be done prior to US.
The cervical length (CL) is obtained by measuring the endocervical canal from the internal cervical os to the external cervical os.
The normal cervix should be at least 30 mm in length. Cervical incompetence is variably defined, however a cervical length of <25 mm at or before 24 weeks is often used. The risk of preterm delivery is inversely proportional to cervical length ref:
- 18% for <25 mm
- 25% for <20 mm
- 50% for <15 mm
Transvaginal scanning is required. In a late 1st trimester scan, opening of the cervical os at rest or in response to fundal pressure is considered an early feature 18
- bulging of the fetal membranes into a widened internal os (considered the most reliable sign 9)
- the appearance of this can worsen from a T shape to a Y shape to a V shape and finally to a U shape.
- if there is complete bulging, it can give a hourglass type appearance
- shortening of the cervical canal
- in severe cases there may be fetal parts or cord that extend through the os
If less than 3 cm, then close follow up.
Considerations include cerclage and steroid for maturation of the fetal lungs.
Cervical incompetence refers to a painless spontaneous dilatation of the cervix, and is a common cause of 2nd trimester pregnancy failure. 1.5% of pregnancies.
Causes:
Idiopathic
Connective tissue disorders
Trauma / surgery
Recurrent miscarriage or termination
Diethylsilbestrol exposure / uterine abnormalities
Presents with pregnancy loss or premature rupture of membranes with oligohydramnios
Fetal fibronectin can rule out premature labour, needs to be done prior to US.
The cervical length (CL) is obtained by measuring the endocervical canal from the internal cervical os to the external cervical os.
The normal cervix should be at least 30 mm in length. Cervical incompetence is variably defined, however a cervical length of <25 mm at or before 24 weeks is often used. The risk of preterm delivery is inversely proportional to cervical length ref:
- 18% for <25 mm
- 25% for <20 mm
- 50% for <15 mm
Transvaginal scanning is required. In a late 1st trimester scan, opening of the cervical os at rest or in response to fundal pressure is considered an early feature 18
- bulging of the fetal membranes into a widened internal os (considered the most reliable sign 9)
- the appearance of this can worsen from a T shape to a Y shape to a V shape and finally to a U shape.
- if there is complete bulging, it can give a hourglass type appearance
- shortening of the cervical canal
- in severe cases there may be fetal parts or cord that extend through the os
If less than 3 cm, then close follow up.
Considerations include cerclage and steroid for maturation of the fetal lungs.
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