The Food and Drug Administration today approved a new type of fetal
monitor that measures oxygen saturation in the baby's blood as a sign of
fetal health during labor and delivery.
Conventional monitors used today measure fetal heart rate (FHR) and
uterine contractions. Physicians use these measurements, along with other
factors, to decide if labor can continue normally or if a Cesarean
delivery is indicated.
The new monitor, the OxiFirst Fetal Oxygen Saturation Monitoring
System, manufactured by Mallinckrodt/Nellcor Perinatal Business,
Pleasanton, Calif., represents the first major technological development
in fetal monitoring since electronic monitoring was introduced in the
1960's and '70s. The system builds on pulse oximetry technology
initially developed in the 70's and 80's by Nellcor for adult and
The OxiFirst system is only to be used along with conventional
electronic fetal monitoring when the fetal
heart rate is "non-reassuring," i.e. when it indicates that the baby may
be in distress due to lack of adequate oxygen. And it is intended for
use only on single (not multiple) fetuses of at least 36 weeks gestation,
where the mother's water has broken and the fetal head is in the normal
vertex position for delivery.
The OxiFirst monitor consists of a fetal sensor that emits and
detects red and infrared light, a connecting cable, and a
microprocessor-controlled monitoring console. The monitor displays fetal
oxygen saturation as the percentage of oxygen in the fetus's blood.
During use, the OxiFirst sensor is inserted into the mother's uterus and
placed against the fetus's temple or cheek.
FDA approval of the system was based on a review of a series of
studies conducted by Mallinckrodt and on the recommendation of the
Obstetrics and Gynecology Devices Panel of FDA's Medical Devices Advisory
Committee, which met in January to review and evaluate this monitor.
In Mallinckrodt's primary study, 508 women were monitored with the
OxiFirst monitor and 502 women received standard labor management without
the OxiFirst monitor. Women monitored with the OxiFirst system were
allowed to continue labor when the fetus had a non-reassuring heart
rate and if the OxiFirst monitor showed that the fetal
oxygen saturation was above 30 percent. The study assessed whether use
of this new monitor would reduce the Cesarean-section rate due to non-
reassuring fetal heart rate.
The primary objective of the study was met. It found that the
Cesarean rate for non-reassuring heart rate was 10 percent in the group
of women monitored conventionally compared to 5 percent in the OxiFirst
group --a significant difference. However, the study also found that the
overall Cesarean rate between the two groups was unchanged. For reasons
not explained by the study, Cesareans for dystocia (difficult labor)
increased in the OxiFirst group.
The study showed that the use of the OxiFirst monitor was safe for
both the mother and fetus. The rate of adverse events was comparable
between the two groups.
Some 3.8 million babies are born each year in the United States, and
perhaps one-fourth of these represent women in labor with non-reassuring
fetal heart rates, a key criteria for possible candidates for this new
To further assess the effect of use of this new monitor on Cesarean
rates, Mallinckrodt will conduct a large study in general medical