ISUOG Practice Guidelines: Intrapartum Ultrasound

Ultrasound in labor is not a proposed standard of care; however, several studies have reported it to be more accurate and reproducible than clinical examination. It is especially helpful in knowing the fetal position and station and prediction of the arrest of labor.

The International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) recently issued practice guidelines for Intrapartum Ultrasound. These Guidelines address exclusively the use of ultrasound in labor to determine fetal head station, position and attitude.

Intrapartum ultrasound can predict mode of delivery (vaginal or operative) and outcome of instrumental vaginal delivery. It is used in the labor ward as an adjunct to clinical digital examination to assess the position of the fetal head, fetal head station, progression, and attitude. 

Ultrasound in labor is performed using a transabdominal or transperineal approach depending upon the clinical situation. A wide-sector, low-frequency (< 4 MHz) exposure is best suited to ultrasound in labor.

Indication for Ultrasound in labor room

Slow progress or arrest of labor in the first or second stage

To determine the fetal head station and position before attempting instrumental vaginal delivery

Assessment of fetal head malpresentation.

While performing ultrasound in labor, data documentation includes fetal viability and FHR, fetal presentation, the position of the spine and occiput, the position of the placenta in relation to the cervix and presenting part.

While performing a transperineal ultrasound, the sonographer should also look for following parameters, especially before operative vaginal delivery (OVD):

Angle of progression (AoP)

Head–perineum distance (HPD)

Head direction with respect to the

pubic symphysis

Midline angle (MLA)

Here is an informative and detailed video by ISUOG about practice guidelines on intrapartum ultrasound

ISUOG practice guideline on intrapartum ultrasound

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Sonographically measured fetal head circumference ≥35 cm at term increases the odds of cesarean delivery.

Sonographically measured fetal head circumference ≥35 cm, within a week of delivery increases the odds of unplanned cesarean section by 75% reports the results of multicenter observational study accepted for publication in American Journal of Obstetrics and Gynecology.

Currently, In US, one in every third baby is born by cesarean section and the high rate is a cause of concern for healthcare industry.

Physicians and patients will be greatly benefited by knowing more about factors that can predict the risk of cesarean section, in terms of better patient counselling and individual labor planning. Besides obstetrics factors, earlier studies have focused on estimated baby weight as a predictor of increased risk of operative and instrumental delivery.

This medical record based study looked at labor outcome of 11,500 primiparous women, presenting at term (37-42 weeks) with singleton fetuses in cephalic presentation for ultrasound with fetal biometry within one week of delivery.

All the patients who had an elective cesarean section were excluded from the study.

It was seen that head circumference ≥35 cm increased the odds of cesarean section by 2.5 times and increased the risk of instrumental intervention by 48%.

Increased head circumference and EFW ≥3900 also increased the risk of prolonged second stage of labor in the study cohort. At the same time head circumference ≥35 cm was significantly associated with improved Apgar score (p=0.01).

The authors concluded that Sonographic fetal head circumference ≥35 cm increased the second stage of labor and is also an independent risk factor for cesarean delivery.

Paired with EFW, increased head circumference ≥35 cm, can be useful for patient counselling and planning the labor. 

Abstract 

External Cephalic Version for breech presenting fetus does not hike the cesarean section rates.

Women who had a successful External Cephalic Version (ECV) are not at increased risk of cesarean section as compared to women who had Spontaneous Cephalic Version (SCV) says the results of a study published ahead of print on August 2, 2017 in Journal of Obstetrics and Gynecology Canada. 

  

This is first study conducted to compare the outcome between spontaneous and external version in breech presenting fetuses.

It is estimated that term fetal malpresentation occurs in about 3% of pregnancies—and is a common indication for cesarean. External Cephalic version is an important tool to reduce the rate of cesarean births in breech presentation.

This secondary analysis of Early External Cephalic Version Trial data identified 931 women who had breech presenting fetuses between 34-36 weeks of pregnancy, but cephalic presentation at term.

Out of these study subjects, 557 women have undergone successful ECV while in 374 women the fetus reverted spontaneously.

Obstetric outcomes between the two groups were comparable: 96 women in ECV arm had Cesarean section as compared to 76 in the SCV group. (adjusted OR [aOR] 0.89; 95% CI 0.63-1.26); 393 had vaginal delivery in ECV arm vs 268 in SCV arm. (aOR 0.92; 95% CI 0.68-1.24).

Women in the ECV had 45% increased odds of undergoing instrumental intervention as compared to women in SCV group. (aOR 1.55; 95% CI 0.96-2.50).

Multiparous women with ECV were half as likely to require a cesarean section as compared to women with spontaneous version or no version at all. ( aOR 0.45; 95% CI 0.26-0.80).

The authors concluded, “Women with a cephalic-presenting fetus at birth as a result of successful ECV are not at greater risk of obstetrical interventions at birth when compared with women with fetuses who spontaneously turn to a cephalic presentation in the third trimester.”

Media Courtesy: American Association of Family Physicians