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'Startling' new pre-birth test reveals babies in distress.

Obstetricians at Washington University School of Medicine in St. Louis are using a "starting" new method that can serve instead of a fetal blood sample to determine whether a fetus is getting enough oxygen during labor. The method, as described in Obstetrics and Gynecology (10/92), may decrease brain damage in infants and reduce the number of unncessary cesarean sections, according to Roy H. Petrie, M.D., professor of obstetrics and gynecology.

The new test entails literally startling the fetus with a sound stimulator that is placed on the mother's abdomen, over the baby's ear. When stimulated, or buzzard, the heart rates of fetuses who are getting enough oxygen go up in the same way the heart rates of adults go up in response to a loud, unexpected noise, Petrie says. But if the heart rate of a fetus does not increase by at least 10 beats a minute for a period of 10 seconds, it is probably not getting enough oxygen and may suffer brain damage is not immediately removed from the womb.

A Problem in Some Pregnancies

Fetal oxgen deprivation is a problem in three to five percent of all pregnancies, according to Petrie. Fetuses who do not have enough oxygen for their metabolism must get their energy from an alternative biochemical pathway that produces lactic acide -- a byproduct that literally fries brain cells.

Physicians have monitored fetal heart rates as a means of detecting fetal distress during labor for the last 15 years. But while a normal heart rate is very accurate for ruling out problems, only 35 to 50 percent of fetuses with abnormal heart rates actually have a problem. "Fetal heart rate monitoring is very good for making a diagnosis of health," Petrie explains. "But when you try to use the same technique to diagnose babies that [sic] may be sick and need to be taken out by cesarean section or by early force of delivery, it's not a very good technique."

Physicians have traditionally used blood analysis to distinguish fetuses with abnormal heart rates who are in distress from those who are not. Fetal blood is collected with a tube-like endoscope that is inserted into the birth canal and used to prick the baby's scalp. Once obtained, the blood is tested for acid-base content, or pH.

Same Information As Blood Sample

Although fetal blood sampling is very accurate, obtaining the sample is very difficult. The new method being used at Washington University yields the same information without having to price the baby in the head or put an already uncomfortable mother into the frog-like position required for blood sampling.

As described in their article, Petrie and colleague Gregg B. Polzin, Karin J. Blakemore, and Erol Amon used both the startling and more conventional blood sampling methods in 100 patients who exhibited abnormal heart rates. The blood pH of those babies whose heart rates accelerated by at least 10 beats per second for 10 seconds were within the normal range; those with lower or no heart accelerations had abnormally acidic pH valves (which could cause brain damage) and were subsequently removed by cesarean section.

Petrie and his fellow researchers not only discovered that heart rate response correlated with blood pH but also identified two different levels of response. Fetuses whose heart rates accelerated 10 beats per second for 10 seconds but less than 15 beats a minute for 15 seconds were more likely to develop problems later in labor, and required closer monitoring than fetuses with greater accelerations.
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Title Annotation:startling the fetus
Author:Will, Kathy
Publication:Nutrition Health Review
Date:Jun 22, 1993
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