"Does 4 cm dilation constitute active labor?" interview with Dr. Emanuel A. Friedman

Emanuel A. Friedman M.D., of Columbia University, introduced the labor curve, commonly known as “Friedman’s Curve ” to depict the average amount of time it took for a labor patient to dilate each cm. Published nearly 60 years ago, the curve is still followed by a majority healthcare providers to define normal labor.

In 2012, when the National Institute of Child Health and Human Development (NICHD), the Society for Maternal and Fetal Medicine (SMFM), and ACOG held a workshop aimed at “preventing the first Cesarean.” In the workshop, it was discussed that many cesarean sections are simply performed because many women are wrongly categorized as “ failure to progress” based on Friedman’s Curve.

In 2014, ACOG and SMFM issued a consensus statement “Safe Prevention of the PrimaryCesarean Delivery ” to bring down the rising cesarean section rates. The statement redefined normal and abnormal labor and stated that Friedman’s Curve should no longer be used as the basis for modern labor management (ACOG 2014).

A critical study published by Zhang et al. formed the basis of the new guidelines. The study was based on data from the Consortium on Safe Labor and looked at labor records of 62,000 women from 19 hospitals across the U.S. The researchers concluded that “ failure to progress” should be diagnosed at 6 cm and not 4 cm as stated earlier.

ACOG also reaffirmed this statement in 2017 and again in 2018 ACOG Committee Opinion No.766: Approaches to Limit Intervention During Labor and Birth.

Here is an interview with Emanuel A. Friedman about definitions of active and in active labor. He opines that “Woman describes her own labor curve, it is irrelevant to designate a particular point in labor as a demarcation between active and in active labor.”

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

Ob/Gyn Updated Facebook page