Cervical Incompetence & Placenta Previa

Transabdominal cervical length measurement requires what condition

Full bladder

When should you switch from transabdominal to transvaginal cervical measurement

When cervical length is < 2.5 cm

If a provider specifically orders cervical length, which method must be used

Transvaginal ultrasound

Gold standard method for evaluating cervical length

Transvaginal ultrasound

What landmarks are used to measure cervical length

Internal os to external os

What structure is used as a guide when measuring cervical length

Cervical canal

Where is the internal os located

Opposite the uterine body curve

Average normal cervical length

3.5 cm

Why must the cervix be observed for more than 3 minutes during transvaginal scan

Because the cervix is dynamic and can change quickly

What changes can occur in the cervix over a short time

Shortening, funneling, dilation

Images taken 20 sec apart!!!!

Definition of cervical incompetence

Inability of the cervix to retain a pregnancy in the second trimester without uterine contractions

How common is cervical incompetence

About 1 in 100 pregnancies

What percentage of second trimester losses is due to cervical incompetence

About 25%

What is another term for incompetent cervix

Cervical insufficiency

What can cervical incompetence lead to

Miscarriage or premature delivery

How often are cervical lengths typically monitored in at-risk patients

Every 2 weeks until 24 weeks

Best imaging method to evaluate cervical incompetence

Transvaginal ultrasound

What measurement is always used when assessing cervical length

External os to internal os

What should you do if you see funneling during scanning

Apply fundal pressure and wait to rule out contraction

Why should you wait if funneling is seen

It may be due to a temporary uterine contraction

What is funneling

Dilatation of the internal os with shortening of cervical length

What shapes can funneling appear as

U-shaped or V-shaped

Which funnel shape is associated with higher risk of preterm delivery

U-shaped funnel

What is a short cervix defined as

Cervical length less than 2.5 cm

What is seen in severe cervical incompetence

Bulging (hourglassing) membranes into the vagina

What does hourglassing refer to

Membranes protruding through the cervix into the vagina

What are common causes of cervical incompetence

Müllerian anomalies,

cervical surgeries,

naturally short cervix,

prior traumatic birth

What is a cerclage

A stitch placed to close the cervix and prevent premature dilation

When is elective (known incompetence) cerclage typically placed

12-14 weeks

What is the success rate of cerclage

80-90%

When are vaginal cerclage stitches typically removed

Around 37 weeks

What are the three types of cerclage

McDonald, Shirodkar, Abdominal

Most common type of cerclage

McDonald

What is special about an abdominal cerclage regarding delivery

Requires cesarean section

What medication may be given in cases of cervical incompetence to help the fetus

Betamethasone

What is the purpose of betamethasone

To help mature fetal lungs in case of preterm birth

What is dilation of the cervix in incompetence

Opening of the internal os with shortening or complete dilation

What is the relationship between short cervix and preterm birth

Increased risk of preterm birth

What is placenta previa

Placenta located near or covering the cervical os

When is placenta previa commonly seen but often resolves

Before 20 weeks of pregnancy

What percentage of early placenta previas remain at term

About 15%

Why does placenta previa often resolve

The uterus grows and the placenta moves upward away from the cervix

What is a false placenta previa

Apparent previa caused by lower uterine segment contraction

What should you do if a contraction mimics previa

Rescan in 10-20 minutes

What must be done before diagnosing placenta previa

Post-void scan or transvaginal ultrasound

Definition of complete placenta previa

Placenta completely covers the internal os

Definition of marginal or low-lying placenta

Placenta is within 2 cm of the internal os but not covering it

What distance defines a low-lying placenta

Within 2 cm of the internal os

What is the main symptom of complete placenta previa

Bright red painless vaginal bleeding in second half of pregnancy

Is bleeding in placenta previa painful or painless

Painless

What activity restriction is common with placenta previa

Restricted from physical exertion

What type of delivery is usually required for complete placenta previa

Cesarean section

When should follow-up ultrasound be done for placenta previa

After 32 weeks

How common is placenta previa

1 out of 200 pregnancies

What should always be identified about the placenta location

Whether it is anterior or posterior

How is placenta previa measured

From internal os to the placental edge

How should a report describe placenta location

Distance from internal os or if it covers the cervix

What are the two main types of placenta previa

Low-lying (marginal) and complete

What is seen in complete previa on imaging

Placenta covering the cervical canal/internal os

What imaging method is best for evaluating placenta previa

Transvaginal ultrasound

Definition of vasa previa

Fetal vessels pass below the presenting part near the cervix

What is the danger of vasa previa

Vessel rupture during membrane rupture causing fetal hemorrhage

What can cause fetal hemorrhage in vasa previa

Tearing of vessels when membranes rupture

How common is vasa previa

About 2 in 10,000 pregnancies

What placental abnormalities are associated with vasa previa

Bilobed placenta, succenturiate lobe, low-lying placenta

What reproductive method is associated with vasa previa

In-vitro fertilization

How is vasa previa best diagnosed

Transvaginal ultrasound with color Doppler

What is the role of color Doppler in vasa previa

To visualize fetal vessels near the cervix