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OBJECTIVE: To assess the association of cervical effacement with the rate of intrapartum cervical change among nulliparous women. METHODS: We conducted a secondary analysis of a prospective trial of intrapartum fetal pulse oximetry. For women who had vaginal deliveries, interval-censored regression was used to estimate the time to dilate at 1-cm intervals. For each given centimeter of progressive cervical dilation, women were divided into those who had achieved 100% cervical effacement and those who had not. The analysis was performed separately for women in spontaneous labor and those who were given oxytocin. RESULTS: A total of 3,902 women were included in this analysis, 1,466 (38%) who underwent labor induction, 1,948 (50%) who underwent labor augmentation (combined for the analysis), and 488 (13%) who labored spontaneously. For women in spontaneous labor, the time to dilate 1 cm was shorter for those who were 100% effaced starting at 4 cm of cervical dilation (P=.01 to

The original expectation of fetal pulse oximetry (FPO) for the field of obstetrics was predicated on the tremendous positive impact pulse oximetry had upon the fields of anesthesiology, critical care medicine, and many other disciplines of medicine. With the general acceptance that many, if not most, concerning fetal heart rate patterns are not associated with significant fetal hypoxemia and acidemia, the additional physiologic information FPO offers (ie, actual arterial blood oxygenation) was believed and hoped by many to be the reassurance that would allow safe avoidance of unnecessary interventions such as cesarean delivery. To date, FPO has not met that expectation, not because of its inability to measure fetal arterial oxygen saturation, but because of its inability to do so with a reduction in overall cesarean deliveries.

The present manuscript reviews recent data on fetal intrapartum surveillance with special attention to new technologies.Continuous fetal heart-rate monitoring, fetal blood sampling, intrapartum stimulation tests, fetal pulse oximetry and fetal electrocardiography will be reviewed.From the available data it appears that to date the analysis of the sinus tachycardia segment of the fetal electrocardiography used in conjunction with continuous fetal heart-rate monitoring is the method of choice.

UNLABELLED: Part II continues by discussing the clinical application of fetal pulse oximetry in intrapartum fetal surveillance as reviewed in the literature. It profiles the predictive ability of fetal pulse oximetry and its correlation with conventional methods of fetal monitoring. In addition, an account is made of its limitations, safety, and acceptability in clinical practice. TARGET AUDIENCE: Obstetricians & Gynecologists, Family Physicians LEARNING OBJECTIVES: After completion of this article, the reader will be able to describe the predictive abilities of fetal pulse oximetry and its correlation with conventional methods of fetal monitoring, to define the critical threshold of fetal oxygen saturation, and to summarize the safety of fetal pulse oximetry.

UNLABELLED: Fetal pulse oximetry has been advocated as a means of improving the specificity of cardioto-cography in intrapartum fetal surveillance. The objective of this article, the first of two reviewing the current literature on fetal pulse oximetry, is to discuss the principles of this new and evolving technology, its development, and the various factors that can affect its readings during fetal monitoring. It serves as a prelude to the second article, which profiles the clinical application of fetal pulse oximetry. Literature pertaining to this topic was selected from a MEDLINE search from 1965 through September 1999, with additional sources obtained through cross-referencing. TARGET AUDIENCE: Obstetricians & Gynecologists, Family Physicians LEARNING OBJECTIVES: After completion of this article, the reader will be able to explain the principles of fetal pulse oximetry, and describe the factors that affect the calibration of fetal pulse oximeters and the factors that affect the fetal pulse oximeter readings.

Since the discovery of the ability to detect fetal heart tones in the 1980s, there has been ongoing research about how to interpret the meaning of these data. Fetal pulse oximetry, also known as fetal oxygen saturation monitoring, is a new method of assessing fetal status during labor that is under investigation in the United States. The article discusses limitations of current methods of fetal assessment, the potential benefits and limitations of fetal oxygen saturation monitoring, and future possibilities for fetal assessment during labor.

More than 5 years ago the Food and Drug Administration approved, conditionally, the OxiFirst Fetal Oxygen Saturation Monitoring System as an adjunct to electronic fetal monitoring. The goal of monitoring was to gain more knowledge of the condition of the fetus by continuously monitoring oxygen saturation when there is a nonreassuring fetal heart rate pattern. The sensor is inserted through the dilated cervix following membrane rupture, and positioned against the fetal face. This randomized trial, conducted at 14 university-based clinical centers, was designed as a means of learning whether adjunctive fetal oximetry lessens the need for cesarean delivery. Participants were nulliparous women with a singleton fetus in cephalic presentation at 36 or more weeks' gestation. The 5341 women in the study were randomized to either “open” fetal pulse oximetry with oxygen saturation values displayed to the clinician, or “masked” oximetry in which the results were hidden. Overall rates of cesarean delivery were 26.3% for the open group and 27.5% for masked monitoring, not a significant difference. The respective operative delivery rates were 7.1% and 7.9% for a nonreassuring fetal heart rate pattern; and 18.6% and 19.2% for dystocia, Findings were similar for the 2168 women in whom a nonreassuring fetal heart rate pattern was identified before randomization. There were no significant differences between the open and masked groups in the rates of forceps or vacuum-assisted delivery, even after excluding women who had labor induced. The relative risk of cesarean delivery associated with knowing the fetal oxygen saturation was 0.96 (95% confidence interval, 0.87–1.04). Neither maternal nor infant complications differed significantly in incidence between the study groups. The sensitivity, specificity, positive predictive value, and negative predictive value of a nonreassuring fetal heart rate pattern for low oxygen saturation (defined as less than 30% for 2 consecutive minutes) were, respectively, 87%, 19.5%, 35%, and 75%. One-fourth of fetuses with a normal heart rate pattern exhibited low oxygen saturation. This large-scale study failed to demonstrate that knowledge of intrapartum fetal oxygen saturation significantly lowers the rate of cesarean delivery or improves infant outcomes. The findings emphasize the need to rigorously evaluate new technologies.

Background The purpose of this study was to compare fetal oxygen saturation by fetal pulse oximetry in parturients with and without epidural labor analgesia in a prospective case control study. Methods Fetal oxygen saturation values were compared in term pregnant women who received epidural analgesia (epidural group) with those in women who did not (control group). Mode of delivery, Apgar score, fetal oxygen saturation, cord blood gas analysis and fetal outcomes were also compared. Results A total of 150 pregnant women (75 in each group) gave written consent and were enrolled. The average fetal oxygen saturation during the first stage of labor (active phase) was 45.6 ± 8.1% for the epidural group and 45.9 ± 7.4% for the control group (NS); saturations for the second stage of labor were 44.9 ± 8.8% and 45.3 ± 6.7%, respectively (NS). In the epidural group, the duration of the first stage of labor was significantly longer (565 ± 217 min) than the control group (434 ± 222 min; P = 0.001). Cesarean delivery rates, neonatal cord blood gas analysis, Apgar scores, and neonatal outcomes were similar in the two groups. Conclusions Fetal oxygen saturation values are similar in the first and second stage of labor in the presence or absence of epidural labor analgesia.

Advances in oximetry have allowed the obstetrician to measure oxygen saturation in the fetus with non-invasive transcutaneous techniques. The influence of caput succedaneum formation on the oxygen saturation results obtained with a pulse oximeter was studied in 30 newborn infants. Caput was associated with a reduced oxygen saturation reading (mean reduction of 15%; P less than 0.001). This effect is partly due to a true drop in local tissue oxygenation but is exacerbated by a systematic error intrinsic to the physics of spectrophotometry. If continuous intrapartum oximetry is ever to become a part of routine obstetric monitoring then probes that pass through the cervix beyond the caput of the presenting part will be required if erroneously low readings are to be avoided.