Fetal Heart Rates During Labor Might Not Be Good Indicator of Fetal Stress

When I was in labor with Big P I was terrified. It was my first birth after 3 miscarriages and I was scared because after about 10 hours of labor I was told my child was not tolerating the contractions. We had the fetal heart monitor on which showed decelerations.  We even had one of those monitors that you place on the baby’s head which showed the same thing — fetal stress.

This is a story many women have for their labors. Sometimes these decelerations lead to medication to speed labor up (which is what happened with Big P) and sometimes these findings lead to a c-section.  A new study was just published this month in the journal Obstetrics and Gynecology shows that the fetal heart rates are not necessarily a good indication of fetal stress and may actually lead to unnecessary interventions.

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The study which was performed by maternal-fetal medicine specialists at Intermountain Medical Center, studied 48,000 labor and delivery cases at 10 Intermountain Healthcare hospitals over a 28-month period. The fetal heart rates were then classified using a system developed in 2008 by the Eunice Kennedy Shriver National Institute of Child Health and Human Development and the American College of Obstetricians and Gynecologists.

The labors were then placed in one of 3 categories:

Category I: heart rate patterns are considered normal and do not indicate fetal stress.
Category II: patterns are considered indeterminate, and their significance uncertain.
Category III: patterns are abnormal and rare, and usually indicate a problem.

Researches analyzed the time that each labor spent in each of the three categories during all stages of labor.  For nearly 78% of the time the labors were classified in Category I; 22% were classified as Category II and only 0.004% were classified as Category III.

Where it gets interesting though is when they looked at the data for only the final 2 hours of labor. The numbers changed to be 61% in Category I; 39% in Category III and category III rates increased to 0.006%.

The researchers then looked at the outcomes of each of these categories and found that those baby’s placed in Category I were found to have APGAR scores no less then 7 at 5 minutes after birth and only 0.2 percent required admission to the neonatal intensive care unit.

Category III fetal heart rates were very uncommon, occurring in only 0.1 percent of the patients, and resulted in admission to the NICU about half the time.

The labors placed in Category II heart rate problems showed up often occurring in 84% of the labors at one time and also found that those classified in this category increased in the two hours before delivery.   Even with those statistics the majority of the babies classified as Category II showed no short-term problems after delivery.

What does this mean according to the researchers?  That using category II heart rate patterns as an indicator of fetal health is an unreliable method of determining if interventions (like c-sections) are needed and may lead to unnecessary procedures and cost.

The researchers are now analyzing the data to determine if there is a more accurate method of determining if those in Category II need interventions and are also looking at preterm babies to see if that makes a difference.

image adapted from Lars Plougmann | Flickr

Article Posted 5 years Ago

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