Improving Fetal Oxygen Status
Improving Fetal Oxygen Status
Abstract & Commentary
By John C. Hobbins, MD, Professor and Chief of Obstetrics, University of Colorado Health Sciences Center, Denver, is Associate Editor for OB/GYN Clinical Alert
Dr. Hobbins reports no financial relationships related to this field of study.
Despite the paucity of information and the discrepancies in the few studies that have addressed the concept, oxygen administration has been utilized in almost every labor floor in the United States to supposedly improve delivery of oxygen to the fetus when an abnormal fetal heart rate pattern is noted. Given the popularity of fetal oxygen saturation monitors in some obstetrical units, I am surprised that a flurry of studies has not emerged to address this question, but the recent publication by Simpson and James suggests that there is reason to employ the above method to improve fetal oxygenation in potentially compromised fetuses.1
The study involved randomizing 56 healthy low-risk women, about to have an induction of labor: 1) to either have a bolus of 1000 cc or 500 cc of fluid, 2) to then be positioned in either left lateral, right lateral, or supine positions, and, last, 3) to either have 15 minutes of 80-100% oxygen delivered by a non-breather anesthetic mask or not. During the entire experimental sequence, the fetus was continuously monitored by an FSpO2 sensor applied to the fetal cheek.
The results were enlightening. Only the 1000 cc bolus increased the oxygen saturation significantly (by 5.2%). Both lateral positions improved the O2 saturation in the fetus over the supine position (average 10% higher), but there was not difference in improvement between the sides. Last, oxygen delivered by mask in a lateral position resulted in a substantial increase in O2 saturation by an average of 8.7% and the rise above baseline lasted for over 10 minutes after the O2 was discontinued. The 4 fetuses who had baselines below 40% saturation had the greatest rise (11.4%).
Commentary
Before this paper surfaced, there was one study suggesting that giving oxygen by mask improved fetal oxygenation while another study did not show this effect. In fact, the "take" of the Cochrane data review was that there was not enough evidence to confirm the benefit of oxygen administration to laboring mothers.
This study simply shows that using the above methods may improve fetal oxygenation and, perhaps, as demonstrated in the four who had a low oxygen saturation below 40%, it might benefit those fetuses who truly were hypoxic.
Nevertheless, these results must be interpreted with caution. One should not take home from this study any suggestion that normal healthy fetuses (as those in this study) would receive a bonus from O2 by mask, and even fetuses displaying variable decelerations would not benefit since other studies have shown that the O2 saturation does not decrease in these fetuses (in the absence of late decelerations or decreased variability).2-6
Is there a downside to continuous oxygen administration by mask? Absolutely! It is confining, is downright scary for some patients, and, for incompletely explained reasons, has been shown to decrease fetal pH when given for more than 10 minutes in the second stage of labor.
Last, this study and every available piece of information in the literature indicates that patients should not be laboring on their backs.
References
- Simpson KR, James DC. Efficacy of intrauterine resuscitation techniques in improving fetal oxygen status during labor. Obstet Gynecol. 2005;105:1362-1368.
- Althabe O Jr, et al. Effects on fetal heart rate and fetal pO2 of oxygen administration to the mother. Am J Obstet Gynecol. 1967;98:858-870.
- Dildy GA, et al. Intrapartum fetal pulse oximetry: the effects of maternal hyperoxia on fetal arterial oxygen saturation. Am J Obstet Gynecol. 1994;171:1120-1124.
- McNamara H, et al. The effect on fetal arteriolar oxygen saturation resulting from giving oxygen to the mother measured by pulse oximetry. Br J Obstet Gynaecol. 1993;100:446-449.
- Thorp JA, et al. The effect of maternal oxygen administration during the second stage of labor on umbilical cord blood gas values: a randomized controlled prospective trial. Am J Obstet Gynecol. 1995; 172(2 Pt 1):465-474.
- Garite TJ, et al. A randomized controlled trial of the effect of increased intravenous hydration on the course of labor in nulliparous women. Am J Obstet Gynecol. 2000;183:1544-1548.
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