Maternal oxygen transport variables during the third trimester of normal pregnancy

OBJECTIVE

The aim of this study was to measure and calculate oxygen transport variables in uncomplicated term pregnancies.

STUDY DESIGN

Ten normotensive primiparous women between 36 and 38 weeks' gestation underwent pulmonary and radial arterial catheterization as part of a larger study. Seven women had studies repeated at approximately 12 weeks post partum. Measurements were made with patients in the left lateral recumbent position after a 30-minute stabilization period. Cardiac output was measured with the thermodilution technique. Blood samples were obtained simultaneously from the pulmonary and radial arteries and analyzed in duplicate for oxygen content with a blood gas analyzer.

RESULTS

The oxygen contents of both arterial and mixed venous blood are significantly lower (P <.05) in the third trimester of pregnancy (15.96 and 11.97 mL/dL, respectively) than in the postpartum period (18.00 and 13.54 mL/dL). The fall in oxygen content during pregnancy prevents any significant increase in oxygen delivery in the third trimester (867. 59 mL/min) relative to the postpartum period (806.50 mL/min, P not significant).

CONCLUSION

This is the first report of directly measured oxygen transport variables in healthy pregnant women.

Institutional influences on the primary cesarean section rate in Utah, 1992 to 1995

OBJECTIVES

Our purpose was to evaluate institutional and organizational influences on cesarean section rates in Utah and to adjust such rates for differences in patient acuity.

STUDY DESIGN

Data on cesarean section rates were derived from the Utah Hospital Discharge Database and adjusted for patient acuity by correcting raw cesarean rates for those patients undergoing cesarean section meeting regional gestational age transport criteria.

RESULTS

When analyzed by means of 1-way analysis of variance, the following factors had a significant negative correlation (P < .05) with cesarean section rate: presence of a newborn intensive care unit and maternal-fetal medicine subspecialists, presence on the medical staff of obstetrician-gynecologist(s) as opposed to family physicians only, delivery volume >1500/y, urban location, and 24-hour in-house anesthesiology. When cesarean rates were corrected for acuity, facilities with maternal-fetal medicine specialists and a newborn intensive care unit had significantly lower rates (P < .001) and more uniform rates than otherwise similar institutions.

CONCLUSIONS

More medically sophisticated physicians and institutions have lower cesarean rates when patient acuity is taken into account.

Videoconferencing: practical advice on implementation

Videoconferencing provides a useful tool for improving information flow, with clinical, educational and administrative uses being particularly relevant to rural and remote Australia. This paper describes the range of possible uses for computer-based videoconferencing and describes the authors' experience in delivering rural medical education in North Queensland via videoconference. Principles that ensure successful videoconferencing are outlined and are applicable to a variety of formats and uses. They include the need to keep it simple, the importance of thorough preparation, and ensuring that education drives technology, rather than the converse.

A prospective evaluation of fetal pericardial fluid in 506 second-trimester low-risk pregnancies

OBJECTIVE

To measure fetal pericardial fluid in low-risk second-trimester pregnancies and to evaluate outcome for those with measurements greater than 2 mm.

METHODS

Five hundred and six women were referred for sonography between 16 and 25 weeks' gestation for common obstetric indications (dating, fetal survey, and placental location) unrelated to an increased risk of anomalies. All cases were evaluated with two-dimensional and M-mode real-time ultrasonography with the use of a mechanical sector transducer. The maximum distance of the fetal hypoechoic cardiac rim was recorded. We reviewed maternal and infant charts for those with measurements greater than 2 mm.

RESULTS

Median (range) maternal age was 25 (15-42) years. Median gravidity and parity were two (1-14) and one (0-11), respectively. Median estimated gestational age was 20.4 (16.3-24.9) weeks. Fetal pericardial fluid was seen in 360 of 506 (71%) fetuses. Of these 360 fetuses, the mean distance (+/- 2 standard deviation) of the fetal hypoechoic cardiac rim was 1.20 mm +/- 0.91 mm (95% confidence interval 1.15, 1.25). Among the 506 cases, the maximum measurement was 3 mm. Ten of the 506 (2%) cases had measurements greater than 2 mm. None of these ten fetuses had a cardiac structural abnormality or arrhythmia, and perinatal outcome was unremarkable.

CONCLUSION

During second-trimester fetal ultrasonographic examination, visualization of pericardial fluid up to 2 mm in the fetus with current high-resolution technology is common and should not be regarded as pathologic.

Monitoring wound healing by odour

A pilot study using electronic aroma detection was performed over a six-month period to assess the aroma of chronic non-healing venous leg ulcers and the effect of appropriate antibiotic therapy on modification of the aroma. Deep infection with pathogenic organisms was found on biopsy culture in 13 out of 15 patients. Odour analysis was performed at weekly intervals on the ulcer dressings using an AromaScan instrument. Data points on the aroma maps moved from their pre-treatment presentation. Alterations in aroma data correlated well with the progress of the ulcers. Aroma analysis is shown to be a potential tool in monitoring the progress towards healing of chronic venous ulcers.

Current status of the multicenter randomized clinical trial on fetal oxygen saturation monitoring in the United States

Current clinical methods of intrapartum fetal assessment are sensitive but poorly specific in detecting fetal compromise during labor. These limitations have substantially contributed to the escalating cesarean section rate which occurred in the US during the last several decades. Experimental and clinical research efforts directed towards application of the oxygen saturation monitor (pulse oximeter) to intrapartum fetal assessment have produced encouraging results. If this new method of fetal assessment is to enter the clinical arena, safety and efficacy issues must first be properly evaluated via randomized clinical trials. The purpose of this report is to describe the design of a multicenter randomized clinical trial of intrapartum fetal oxygen saturation monitoring recently begun in the US. Specific aspects of the trial, including purpose, study design, sample size estimates, control and test groups, inclusion and exclusion criteria, fetal heart rate classification, definition of normal fetal arterial oxygen saturation (SpO2), clinical management protocol, and assessment of maternal-fetal outcomes will be addressed.

Prospective evaluation of the antenatal incidence and postnatal significance of the fetal echogenic cardiac focus: a case-control study

OBJECTIVE

We evaluated the antenatal incidence and postnatal significance of echogenic cardiac foci observed during antenatal ultrasonography.

STUDY DESIGN

During a 4-month period, all women undergoing dating ultrasonography between 16.0 and 24.9 weeks' gestation at one referral center were prospectively evaluated for an echogenic cardiac focus during an apical four-chamber view of the heart. Referrals for maternal or fetal complications were excluded. Postnatal echocardiography was performed for those identified with positive findings. Controls were selected from among normal subjects in the general group for comparison with the study group.

RESULTS

Five hundred six consecutive fetuses were evaluated at a mean +/- SD gestational age of 20.6 +/- 1.6 weeks. There were 25 (4.9%) fetuses found to have echogenic cardiac focus (left ventricle = 19, right ventricle = 6). Echocardiography was performed between 0.3 and 20.1 weeks postdelivery. After birth, 12 echogenic left ventricle papillary muscles and three echogenic left ventricle chordae were identified; there were no postnatal right ventricle findings. There were no cases of intracardiac tumor or myocardial dysfunction; one neonate had minor structural malformations. There were no significant differences in maternal age, gravidity, parity, gestational age at ultrasonography, gestational age at delivery, or 5-minute Apgar scores. A significant difference was observed in birth weight between the control (n = 50) and study (n = 25) groups (3465 +/- 501 gm vs 3124 +/- 589 gm; p = 0.002). This difference persisted after correcting for gestational age, although all infants in both groups born after 37.0 weeks weighed > 2500 gm.

CONCLUSIONS

The incidence of echogenic cardiac foci during routine midtrimester ultrasonography is 4.9%. As an isolated finding, the echogenic cardiac focus may be associated with a statistically significant but clinically insignificant decrease in birth weight. Because of these findings, we consider an isolated echogenic cardiac focus in a patient at low risk for cardiac abnormalities a variant of normal, which does not warrant follow-up clinical evaluation.

Very advanced maternal age: pregnancy after age 45

OBJECTIVE

Our purpose was to describe the maternal and fetal outcomes of pregnancies in women > or = 45 years old at delivery.

STUDY DESIGN

A retrospective review of in-hospital deliveries after 20 weeks of gestation was performed in four Utah tertiary care hospitals for the 10-year period between 1985 and 1994.

RESULTS

Seventy-nine cases were identified among 126,500 births, with an incidence of 0.63 per 1000 births. Maternal ages were 45 (n = 44), 46 (n = 21), and > or = 47 (n = 14) years. Three of the conceptions were assisted, including both twin gestations. Thirty-seven (46.8%) had obstetric complications during pregnancy; the most frequent complications were gestational diabetes (12.7%) and preeclampsia (10.1%). Median (range) gestational age at delivery was 39 (22.9 to 41.7) weeks; 12 (15.2%) deliveries occurred before 37 weeks. Eight (9.9%) karyotype abnormalities were diagnosed. The cesarean section rate was 31.7%; the most frequent indications were abnormal lie (n = 9), fetal distress (n = 5), and previous cesarean delivery (n = 5). There were no maternal deaths. Median (range) birth weight was 3466 (397 to 5085) gm; 14 (17.3%) were < 2500 gm and 16 (19.8%) were > 4000 gm. Twelve (14.8%) infants were admitted to the neonatal intensive care unit. The corrected perinatal mortality rate was 1.3% (1/78).

CONCLUSIONS

In women > 45 years old at delivery maternal and fetal outcomes were generally good, but there was a high incidence of pregestational (chronic hypertension, hypothyroidism) and gestational (karyotype abnormalities, gestational diabetes, cesarean section, macrosomia) complications. This information may be helpful for counseling women between 45 and 50 years old who are considering pregnancy.

The relationship between oxygen saturation and pH in umbilical blood: implications for intrapartum fetal oxygen saturation monitoring

OBJECTIVE

Our purpose was to evaluate the relationship between umbilical arterial blood oxygen saturation determined by hemoximetry (Sao2) and umbilical arterial blood pH and base excess determined by blood gas analysis to establish a "critical threshold" for fetal preductal arterial oxygen saturation determined by reflectance pulse oximetry (Spo2).

STUDY DESIGN

Umbilical artery and vein blood specimens were obtained at delivery. Blood gas analysis and hemoximetry were performed. Polynomial regression analysis and receiver-operator characteristic curves were calculated for umbilical arterial blood Sao2 and theoretic preductal arterial blood Sao2 versus umbilical arterial blood pH and base excess.

RESULTS

A total of 1101 paired umbilical artery and vein specimens were obtained. When the umbilical arterial blood Sao2 was > or = 30%, umbilical arterial blood pH was > or = 7.13 in 99.0% (388/392) of cases and < 7.13 in 1.0% (4/392) of cases. When umbilical arterial blood Sao2 was < 30%, umbilical arterial blood pH was > or = 7.13 in 91.4% (648/709) of cases and < 7.13 in 8.6% (61/709) of cases.

CONCLUSIONS

From these analyses, it appears that an Spo2 cutoff value of 30% would be reasonable in clinical trials of intrapartum fetal pulse oximetry.

The effects of maternal position and cardiac output on intrapulmonary shunt in normal third-trimester pregnancy

OBJECTIVE

To assess the effect of pregnancy, maternal position, and cardiac output on intrapulmonary shunting (Qs/Qt) in normotensive nulliparous women near term.

METHODS

Ten normotensive nulliparas between 36 and 38 weeks' gestation underwent pulmonary artery catheterization (via the subclavian route) and radial artery canalization. Baseline assessments were made with subjects in the left lateral recumbent position after a 30-minute stabilization period. Measurements were obtained sequentially in the left lateral, right lateral, supine, knee-chest, sitting, and standing positions. Each position change was followed by a 10-minute pre-measurement stabilization period. Cardiac output was measured via the thermodilution technique. Blood samples were obtained simultaneously from the pulmonary and radial arteries and analyzed in duplicate for oxygen content with a blood gas analyzer. Qs/Qt was calculated using the classic shunt equation. Statistical analysis was performed by analysis of variance of repeated measures of Qs/Qt and maternal position. The relationship of Qs/Qt to maternal cardiac output was evaluated by the correlation coefficient. Significance was defined as P < .05.

RESULTS

Directly measured Qs/Qt averaged 15.3% in left lateral, 15.2% in right lateral, 13.9% in supine, 12.8% in knee-chest, 13.8% in sitting, and 13.0% in standing positions. There was no statistically significant correlation between Qs/Qt and cardiac output (R2 = 0.11, not significant).

CONCLUSION

This is the first report of directly measured Qs/Qt in normal pregnant women in the third trimester. Qs/Qt values reported in pregnancy are higher than those reported in nonpregnant individuals.

Third-trimester arterial blood gas and acid base values in normal pregnancy at moderate altitude

OBJECTIVE

To report arterial blood gas and acid base values of normal nulliparous patients at moderate altitude for commonly used maternal positions.

METHODS

Ten normotensive nulliparous women between 36 and 38 weeks' gestation volunteered to undergo radial and pulmonary artery cannulation as part of a larger study. Following instrumentation, baseline assessments were made in the left lateral recumbent position after a 30-minute stabilization period. Sequential measurements were then obtained in the left lateral, right lateral, supine, knee-chest, sitting, and standing positions. Blood samples were analyzed in duplicate for oxygen content on a blood gas analyzer. Statistical analysis was performed by analysis of variance of repeated measures with significance defined at P < or = .05.

RESULTS

There was no significant difference in arterial blood gas or acid base values between any positions in this antepartum population of term healthy women. The composite mean values were as follows: pH 7.46, arterial carbon dioxide pressure (PaCO2) 26.6 mmHg, arterial oxygen pressure 88.3 mmHg, bicarbonate 18.2 mEq/L, saturated arterial hemoglobin level 0.96.

CONCLUSION

Arterial blood gas and acid base values are not altered by maternal position in the late third trimester of pregnancy. The PaO2 in these women studied at moderate altitude was lower than previously reported for healthy pregnant women studied at sea level. Appropriate interpretation of arterial blood specimens of pregnant women should take into account both the pregnancy and altitude at which the women reside.

Intrapartum fetal pulse oximetry: past, present, and future

Oxygen saturation monitoring (pulse oximetry) has markedly improved medical care in many fields, including anesthesiology, critical care, and newborn intensive care. In obstetrics, fetal heart rate monitoring remains the standard for intrapartum assessment of fetal well-being. Fetal heart rate monitoring is sensitive but nonspecific for detecting fetal compromise. Additional clinical information is needed to discern those fetuses not at risk for development of intrapartum acidosis to avoid unnecessary intervention. Fetal oxygen saturation monitoring is a new technique currently under development. This article reviews the evolution of intrapartum fetal oxygen saturation monitoring and proposes directions for future investigation.

Normal values for amniotic fluid index during uncomplicated twin pregnancy

OBJECTIVE

To establish the gestational age trends of amniotic fluid index (AFI) in uncomplicated twin pregnancies.

METHODS

Amniotic fluid index was measured in uncomplicated twin pregnancies seen between 1985 and 1993 and meeting the following criteria: 1) no maternal medical or obstetric complications, 2) normal growth of both twins by serial ultrasound, and 3) normal amniotic fluid volume by ultrasound. Amniotic fluid index was measured by adding the deepest vertical pockets in four quadrants, defined by the umbilicus and linea nigra. The relation between gestational age and AFI was evaluated using linear regression analysis.

RESULTS

Two hundred eighty-two sets of twins were considered uncomplicated; 1101 AFI measurements were performed on these pregnancies between 25.5 and 40.5 weeks' gestation. Percentile values for AFI were determined according to gestational age. The regression equation relating the median AFI to gestational age was: AFI = 19.4 - 0.12 x gestational age (P = .03). The R2 value was 0.04.

CONCLUSION

Gestational age trends in normative AFI measurements for twin pregnancies have been established. Their use will facilitate a more reproducible, quantitative diagnosis of oligohydramnios in twins, compared with subjective, qualitative approaches to amniotic fluid volume assessment.

Amniotic fluid index and perinatal morbidity

Our purpose was: (1) to determine whether assessment of amniotic fluid index in high risk patients with a reactive nonstress test (NST) allowed improved recognition of the fetus at risk for perinatal morbidity than a reactive NST alone; and (2) to determine the optimal low amniotic fluid index (AFI) which should prompt clinical concern. The last NST performed within a week of delivery and amniotic fluid index were retro-spectively compared with various indices of perinatal morbidity. In fetuses with a reactive NST, decreasing AFI was directly correlated with a risk of 5-minute Apgar score of less than 7 and delivery for fetal distress. When various subgroupings of AFI were compared, 7 cm or greater appeared to have a better inverse correlation with the indices of morbidity than lower cut-off values. The addition of AFI assessment to the standard NST allows better prediction of perinatal morbidity than the NSTs alone. Seven centimeters appears to be a reasonable cut-off for clinical concern.

Amniotic fluid epidermal growth factor levels in normal and abnormal pregnancies

OBJECTIVE

To determine the concentrations of epidermal growth factor (EGF) in amniotic fluid (AF) from women during late pregnancy, with and without pathophysiologic complications.

METHODS

All AFs were collected by amniocentesis from the following groups: gestational age at least 38 weeks (n = 15); gestational age 36-37 weeks (n = 10); gestational age 35 weeks (n = 5); labor 34 weeks or less, delivered within 7 days (n = 10); labor 34 weeks or less, undelivered (n = 10); chorioamnionitis (n = 7); gestational age-matched controls (n = 7); term, in labor (n = 8); term, not in labor (n = 8); intrauterine growth restriction (IUGR) 38 weeks or more (n = 8); macrosomia at 38 weeks or more (n = 10). Epidermal growth factor was assayed using a specific radioimmunoassay.

RESULTS

Amniotic fluid EGF levels increase rapidly in late pregnancy but are not altered by chorioamnionitis or by term or preterm labor. Intrauterine growth restriction is associated with lower EGF levels in AF, but macrosomia is without effect.

CONCLUSIONS

Epidermal growth factor levels in AF are increased near term and decreased in pregnancies complicated by IUGR; they may be an indicator of specific maturational events.

Cardiac arrest during pregnancy

Cardiac arrest occurs rarely in pregnancy. Nevertheless, the practicing obstetrician stands a likely chance of encountering this acute condition at least once over the course of a busy career. A basic understanding of maternal-fetal physiology and the acute management of cardiac arrest are of key importance. ECC is not significantly changed from that administered to the nonpregnant patient. Factors unique to pregnancy, however, such as lateral uterine displacement, effects of drugs on the mother and the fetus, and the issues of perimortem cesarean section should be understood by the consulting obstetrician. The critical period in management of these patients is within the first several minutes of the event. In many situations, the obstetrician may be the first to arrive and initiate therapy before the arrival of multidisciplinary assistance. Prompt initial management will give the mother and fetus the best chances for survival.

Amniotic fluid embolism: analysis of the national registry

OBJECTIVE

We analyzed the clinical course and investigated possible pathophysiologic mechanisms of amniotic fluid embolism.

STUDY DESIGN

We carried out a retrospective review of medical records. Forty-six charts were analyzed for 121 separate clinical variables.

RESULTS

Amniotic fluid embolism occurred during labor in 70% of the women, after vaginal delivery in 11%, and during cesarean section after delivery of the infant in 19%. No correlation was seen with prolonged labor or oxytocin use. A significant relation was seen between amniotic fluid embolism and male fetal sex. Forty-one percent of patients gave a history of allergy or atopy. Maternal mortality was 61%, with neurologically intact survival seen in 15% of women. Of fetuses in utero at the time of the event, only 39% survived. Clinical and hemodynamic manifestations were similar to those manifest in anaphylaxis and septic shock.

CONCLUSIONS

Intact maternal or fetal survival with amniotic fluid embolism is rare. The striking similarities between clinical and hemodynamic findings in amniotic fluid embolism and both anaphylaxis and septic shock suggest a common pathophysiologic mechanism for all these conditions. Thus the term amniotic fluid embolism appears to be a misnomer.

Regulation of G-protein alpha i2 subunit expression by oxidized low-density lipoprotein

Oxidized low-density lipoprotein (LDL) inhibits signalling pathways mediated by pertussis toxin-sensitive guanine nucleotide-binding proteins (Gi proteins). To determine whether this inhibition is due to altered G protein alpha i subunit expression, mRNA and protein levels of alpha i isoforms were assessed in bovine aortic endothelial cells treated with oxidized LDL (0-100 micrograms/ml, 0-72 h). Oxidized LDL did not affect the expression of alpha i3, but did cause time- and concentration-dependent decrease in alpha i2 mRNA and protein resulting in a 3.2- and 3.5-fold reduction, respectively, after 72 h. This decrease in alpha i2 coincided with a 86% decrease in alpha i2 GTPase activity. Nuclear run-off studies did not show any significant effect of oxidized LDL on alpha i2 or alpha i3 transcription. In the presence of actinomycin D, oxidized LDL shortened the t1/2 of alpha i2 mRNA from 16 h to 8 h which was attenuated by cycloheximide. In addition, pulse-chase labelling with [35S]methionine revealed that oxidized LDL reduced the t1/2 of alpha i2 protein from 27 to 14 h. Our results indicate that oxidized LDL can modulate receptor-Gi coupling by downregulating the expression of alpha i2, but not alpha i3. The mechanism involves both mRNA destabilization and protein degradation.

Oxidized low-density lipoprotein decreases the expression of endothelial nitric oxide synthase

The atherogenic effects of low-density lipoprotein (LDL) may be mediated, in part, by its effect(s) on endothelial-derived nitric oxide (NO). To determine whether LDL can modulate NO production by changing NO synthase expression, we treated human saphenous vein endothelial cells with increasing concentrations of native or oxidized LDL (0-100 micrograms/ml) for various durations (0-72 h). Oxidized, but not native LDL caused a time-dependent decrease in steady-state NO synthase mRNA levels. This coincided with a maximal 56% decrease in NOS activity was determined by [3H]arginine to [3H]citrulline conversion. In the presence of actinomycin D, treatment with oxidized LDL reduced the half-life of NO synthase mRNA from 36 to 10 h. This decrease in NO synthase mRNA correlated with the degree of LDL oxidation and was attenuated by pretreatment with cycloheximide. Nuclear run-off studies showed a biphasic transcriptional pattern of NO synthase gene with an initial 25% decrease during the first 6 h followed by a maximal 2.2-fold increase over baseline during the subsequent 18 h. These results indicate that oxidized LDL regulates endothelial NOS expression through a combination of early transcriptional inhibition and post-transcriptional mRNA destabilization.

Brachial plexus palsy involving the posterior shoulder at spontaneous vaginal delivery

Brachial plexus injuries sustained at birth have most often been attributed to the maneuvers performed when attempting to relieve a shoulder dystocia or to deliver a breech vaginally. In the case now reported, the brachial plexus injury involved the posterior shoulder. As the delivery was spontaneous and without forceps or manual rotation, with delivery effected using only the McRobert's maneuver, it is hypothesized that maternal expulsive forces in conjunction with lodging of the posterior shoulder on the sacral promontory resulted in the injury.

Intrapartum fetal pulse oximetry: the effects of maternal hyperoxia on fetal arterial oxygen saturation

OBJECTIVE

Our purpose was to observe the effects of maternal oxygen administration on fetal arterial oxygen saturation in normal human fetuses during labor.

STUDY DESIGN

Twenty healthy women with uncomplicated pregnancies were studied during active labor at term. Arterial oxygen saturation was measured by a noninvasive reflectance pulse oximeter designed for fetal application (Nellcor, Inc, Pleasanton, Calif.). The first group was studied during 20-minute intervals of inspired oxygen concentrations of 21%, 40%, and 100%. In a second group the effects of prolonged (45 minutes) supplemented 40% oxygen administration were evaluated. Differences between groups were analyzed by analysis of variance; significance was considered at p < 0.05.

RESULTS

A significant increase in fetal arterial oxygen saturation (50% +/- 8% vs 64% +/- 6%, p < 0.0001) was detected in the group given 100% oxygen for 20 minutes but not in the groups that received 40% oxygen for 20 or 45 minutes.

CONCLUSIONS

Prolonged maternal administration of 40% oxygen resulted in no significant demonstrable change in fetal arterial oxygen saturation determined by reflectance pulse oximetry in normal fetuses. Because the administration of oxygen by standard mask techniques rarely results in 40% inspired oxygen concentration, fetal benefits of such intrapartum maternal oxygen administration are questionable.

Intrapartum fetal pulse oximetry: fetal oxygen saturation trends during labor and relation to delivery outcome

OBJECTIVES

Our purpose was to study fetal arterial oxygen saturation trends by continuous pulse oximetry during labor in subjects with normal and abnormal delivery outcomes.

STUDY DESIGN

Continuous fetal arterial oxygen saturation was measured during labor with a noninvasive reflectance pulse oximeter designed for fetal application. Averaged arterial oxygen saturation values were compared between stage 1 and stage 2 of labor, with stage 1 further subdivided into early (< or = 4 cm), middle (5 to 7 cm), and late (8 to 10 cm) phases. Delivery outcome was considered to be abnormal for any of the following conditions: gestational age < 37 weeks, maternal oxygen administration, delivery by cesarean section, 5-minute Apgar score < 7, umbilical artery pH < 7.10, birth weight < 2500 gm, or newborn intensive care unit admission.

RESULTS

A total of 291 subjects were studied: 142 in Provo, 90 in Nijmegen and 59 in San Francisco. Subjects with delivery complications (n = 125) were evaluated separately from those with normal delivery outcomes (n = 160). Fetal arterial oxygen saturation was 58% +/- 10% (mean +/- SD) during the cumulative period of study for the normal-outcome group. A significant decrease (paired t test, p < 0.001) in fetal arterial oxygen saturation occurred from stage 1 (59% +/- 10%) to stage 2 (53% +/- 10%) labor. When stage 1 was subdivided into early (< or = 4 cm), middle (5 to 7 cm), and late (8 to 10 cm) phases, a gradual decreasing trend in fetal arterial oxygen saturation was observed: 62% +/- 9%, 60% +/- 11%, and 58% +/- 10%.

CONCLUSIONS

With the use of reflectance pulse oximetry, a statistically significant decrease in fetal arterial oxygen saturation was observed during labor in women with normal and abnormal delivery outcomes.