Fetal Blood Gases Research Articles

Supplemental Oxygen Study: A Randomized Controlled Study on the Effect of Maternal Oxygen Supplementation during Planned Cesarean Delivery on Umbilical Cord Gases.

The aim was to determine the fetal umbilical blood gas effects of supplemental maternal oxygenation compared with room air (RA) during term planned cesarean delivery. This is a prospective randomized controlled study of singleton planned cesarean deliveries randomized to receive supplemental oxygen (O2) at 10 L per minute (L/min) via facemask or RA. Umbilical cord gases were collected. The primary outcome was umbilical arterial pH level. Secondary outcomes included umbilical cord values and maternal and neonatal outcomes. Data were expressed as median ± interquartile range (IQR). Seventy subjects in total were enrolled, with 65 subjects available for analysis. The median umbilical arterial pO2 was significantly increased in the supplemental O2 group (18 [13.5-20.5] mm Hg) versus RA group (16 [12-18] mm Hg), p = 0.04). The median umbilical venous pO2 was significantly increased in the supplemental O2 group (32 [26.5-36.0] mm Hg) versus RA group (28.5 [22-34.3] mm Hg), p = 0.04). There were no significant differences with other umbilical blood gas values and composite maternal or neonatal complications. Subjects with term singleton gestations receiving O2 at 10 L/min during cesarean delivery compared with RA demonstrated no significant change in umbilical cord pH values. There was a significant increase in umbilical cord arterial and venous O2 levels in those receiving O2.

Acidemia in neonates with a 5-minute Apgar score of 7 or greater – What are the outcomes?

The Apgar score is universally used for fetal assessment at the time of birth, whereas, the collection of fetal cord blood gases is performed commonly in high-risk situations or in the setting of Apgar scores of <7, which is a less standardized approach. It has been well-established that neonatal acidemia at the time of delivery can result in significant neonatal morbidity and death. Because of this association, knowledge of the fetal acid-base status and detection of acidemia at the time of delivery can serve as a sensitive and useful component in the assessment of a neonate's risk. Umbilical cord blood gas analysis is an accurate and validated tool for the assessment of neonatal acidemia at the time of delivery. Because the collection of fetal cord blood gases is not a standardized practice, it is possible that, with such a varied approach, some cases of neonatal acidemia are not detected, particularly in the setting of reassuring Apgar scores. In a setting of universally obtained cord blood gases, we sought to identify the rates of acidemia and associated factors in neonates with 5-minute Apgar scores of ≥7. This retrospective cohort study identified all term, singleton, nonanomolous neonates with 5-minute Apgar scores of ≥7. The incidence of umbilical artery pH ≤7.0 or ≤7.1 and base excess ≤-12 mmol/L or ≤-10 mmol/L were examined overall and in association with obstetric complications and adverse neonatal outcomes. Chi-squared tests were used to compare proportions, and multivariable logistic regression was used to control for potential confounders. In this cohort, the incidence of an umbilical artery pH of ≤7.0 was 0.5%, of a pH ≤7.1 was 3.4%, of a base excess ≤-12 mmol/L was 1.4%, and of ≤-10 mmol/L was 4.0%. Rates of neonatal acidemia were greater in the setting of meconium (4.3% vs 3.2%; P<.001), placental abruption (13.2% vs 3.4%; P<.001), and cesarean deliveries (5.8% vs 2.8%; P<.001), despite normal 5-minute Apgar scores. Additionally, umbilical artery pH ≤7.0 was associated with an increased risk of respiratory distress syndrome (adjusted odds ratio, 6.5; 95% confidence interval, 2.9-14.3) and neonatal intensive care unit admission (adjusted odds ratio, 10.8; 95% confidence interval, 6.8-17.4). Base excess of ≤-12 mmol/L was also associated with an increased risk of neonatal sepsis (adjusted odds ratio, 4.7; 95% confidence interval, 1.9-12.1). Finally, when examined together, neonates with both a pH of ≤7.0 and base excess of ≤-12 mmol/L continued to demonstrate an increased risk of neonatal intensive care unit admission and respiratory distress syndrome, with adjusted odds ratios of 9.6 and 6.0, respectively. This risk persisted in neonates with a pH of ≤7.1 and base excess of ≤-10 mmol/L as well, with adjusted odds ratios of 4.5 and 1.1, respectively. Because neonates with reassuring Apgar scores have a residual risk of neonatal acidemia that is associated with higher rates of adverse outcomes, the potential utility of obtaining universal cord blood gases should be further investigated.

Maternal and fetal arterial blood gas data during general anaesthesia for caesarean delivery of preterm twin lambs.

Much remains to be understood with regards the effects of prolonged anaesthesia on maternal and fetal haemodynamics and oxygenation. With the aim of improving anaesthetic management of pregnant sheep undergoing recovery surgery under anaesthesia, paired maternal and fetal arterial blood samples were collected during caesarean delivery of twin preterm lambs to document the blood gas status of the ewe and fetus. Twenty-one Merino twin pregnant ewes at 126 (±1) days of gestation were anaesthetized for caesarean delivery of their fetuses. Arterial blood samples were collected from the radial artery of the ewe and umbilical artery of the fetus at the point of delivery. There was a significant difference between maternal PaCO2 and end-tidal CO2 and alveolar and arterial PaO2, indicating ventilation perfusion mismatch. Interestingly, the ewes were anaemic but the fetuses were not. These data underscore the need to undertake further work to determine the optimal anaesthetic regimen for twin pregnant ewes at different gestational ages in a biomedical research setting.

To compare intrapartum cardiotocographic (CTG) recording with conventional intermittent fetal heart auscultation during labor

Standard evaluation of fetal well-being during labor includes the periodic assessment of the fetal heart rate (FHR), its pattern and response to intrapartum stimuli and events. Effective methods of evaluation and meaningful interpretation of FHR data range from non-invasive techniques like Intermittent Auscultation, continuous electronic fetal heart rate (FHR) monitoring to invasive techniques of fetal blood gas analysis and fetal ECG.

Comparing fetal scalp lactate and umbilical cord arterial blood gas values

Fetal scalp lactate has been shown to be as effective as scalp pH in predicting fetal outcomes. However, there is limited clinical evidence to demonstrate a strong correlation with fetal acidaemia at birth. To compare the diagnostic accuracy of fetal scalp lactate and umbilical cord arterial blood gas values sampling, as it is used in clinical practice. A retrospective cohort study was performed on 661 term (≥37 weeks) births where a fetal scalp lactate sample was taken during labour. Cases were excluded where either the lactate was taken greater than 1 h prior to delivery, incomplete cord gas analyses were available, or a sentinel hypoxic event occurred prior to delivery. The final data set included 229 microvolume scalp lactate measurements which were compared with neonatal paired cord blood gas values taken at delivery. A fetal scalp lactate measurement of ≥4.8 mmol/L had a positive predictive value (PPV) of 1% and a negative predictive value (NPV) of 100% in predicting umbilical artery pH ≤7.00, and a PPV of 5% and a NPV of 98% in predicting umbilical artery pH ≤7.10. The sensitivity and specificity for these values were 100%, 23% and 90%, 23%, respectively. Fetal scalp lactate microsampling has a strong negative predictive value for fetal acidaemia at birth.

30(+) years of exercise in pregnancy.

In 1980 I came to Loma Linda to study maternal exercise, with Dr. Longo as my mentor. For millennia strenuous exercise was considered harmful for the fetus. Early studies reinforced that idea, by showing that exercise reduced uterine blood flow and fetal PO2 by up to 40 and 29 %, respectively. But utero-placental reserve is ~50 %. So why was fetal PO2 so much reduced during exercise?Methods proved to be important. It took chronically instrumented animals accustomed to the laboratory environment, experiments standardized to fitness of the individual (%VO2max), measurement of total uterine blood flow, and blood gas values corrected for body temperature. The results were simple and hold till this day. Uterine blood flow decreases linearly with maternal heart rate increase, which depends on exercise intensity and duration. Maximal reduction in uterine blood flow is ~20 % and uterine O2-uptake remains unaltered because blood flow reduction is compensated by increases in hematocrit and uterine O2-extraction. Fetal body temperature increases with that of the mother by ~2 °C at maximal exercise and fetal blood gas values are little affected by exhaustive maternal exercise, if properly corrected for temperature. So I left Loma Linda knowing that pregnant sheep can exercise to exhaustion without harm to the fetus, thanks to effective compensatory mechanisms.After returning to Erasmus University Rotterdam further studies in humans showed that physical fitness is unaffected by pregnancy, weight-gain affects performance, and strenuous exercise in healthy pregnant women does not harm the fetus. Thus, the millennia-old perspective has changed.

Ontogeny and control of the heart rate power spectrum in the last third of gestation in fetal sheep

Power spectral analysis of fetal heart rate variability has been proposed to provide a non-invasive estimate of autonomic balance. However, there are few systematic data before birth. We therefore examined developmental changes in the frequency power spectrum at very low (0-0.04 Hz), low (0.04-0.15 Hz) and high frequencies (0.15-0.4 Hz), as well as the ratio of low- to high-frequency power (LF/HF), in chronically catheterized, healthy fetal sheep at 0.6 (n = 8), 0.7 (n = 7) and 0.8 gestational age (ga; n = 11). In a second study, 0.8 ga fetuses received either atropine (4.8 mg bolus, then 4.8 mg h(-1) for 30 min, n = 6) or 6-hydroxydopamine (20 mg ml(-1) at 2.5 ml h(-1) for 3 h; n = 9). Data were analysed by sleep state, defined by low-voltage-high-frequency (LV) or high-voltage-low-frequency (HV) EEG. Total spectral power increased with gestational age (P < 0.05), while LF/HF decreased from 0.6 to 0.7 ga. At 0.8 ga, heart rate and LF/HF were significantly higher during HV than LV sleep (P < 0.05). Consistent with this, although total spectral power was not significantly greater during HV sleep, there was a significant interaction between sleep state and frequency band (P = 0.02). Both atropine (P = 0.05) and 6-hydroxydopamine (P < 0.05) were associated with an overall reduction in spectral power but no significant effect on the LF/HF ratio. This study does not support substantial, consistent differences between the frequencies of sympathetic and parasympathetic activity in late-gestation fetal sheep.

Changes in fetal lamb arterial blood gas and acid-base status with advancing gestation

To determine whether there are changes in blood gas and acid-base status with advancing gestation in the fetal lamb, similar to that reported in the human fetus, blood gas, acid-base, and blood metabolite values were measured in 447 control, arterial blood samples from 108 chronically instrumented fetal lambs between 103 and 146 days gestation. With advancing gestation, Po(2), pH, O(2) saturation, and O(2) content fell significantly, while Pco(2) and hemoglobin concentration increased. Blood glucose and lactate concentrations were unchanged, although the lactate level increased with decreasing Po(2), particularly when below ~13 mmHg. Multiple linear regression indicated that increasing fetal number was associated with decreased Po(2) and glucose level and increased pH, HCO(3)(-), base excess, and lactate concentration. Hemoglobin concentration was higher in female than male lambs. Overall, there was a linear relationship between glucose concentration and birth weight. It is concluded that in fetal lambs as in the human fetus, there are changes in blood gas and acid-base status with advancing gestation. This may be due to the decrease in fetal weight-normalized uterine and umbilical blood flows than occurs in these and other species as gestation proceeds. In addition, the reduced birth weight in twin and triplet lambs may be due to hypoglycemia rather than hypoxemia.

Comparison of the maternal and neonatal effects of bupivacaine plus fentanyl and ropivacaine plus fentanyl during cesarean delivery

The aim of the present study was to compare the anesthetic efficacy, and fetal and maternal effects of 7.5 mg (1 ml) intrathecal 0.75% hyperbaric ropivacaine + 25 μg (0.5 ml) fentanyl versus 5 mg (l ml) intrathecal 0.5% hyperbaric bupivacaine + 25 μg (0.5 ml) fentanyl in elective cesarean delivery. The study included 40 ASA I-II cases scheduled for cesarean delivery that were randomized into two groups of 20 cases each. Cases in the RF group were administered 0.75% hyperbaric ropivacaine + 25 μg (0.5 ml) fentanyl and those in the BF group were administered 5 mg (l ml) hyperbaric bupivacaine + 25 μg (0.5 ml) fentanyl into the spinal space. The time until spinal anesthesia in the T4 dermatome, overall duration of analgesia, hemodynamic parameters, Apgar score of newborns at 1-5 min, fetal blood gas values (pH, PO2, PCO2, HCO3-, and BE), maternal side effects, the degree of motor block, maternal need for ephedrine, objective pain scale score, and patient satisfaction were recorded in each group. There were no significant differences between the groups in terms of the parameters evaluated (P > 0.05). In elective cesarean delivery, the combinations of bupivacaine + fentanyl or ropivacaine + fentanyl exhibited similar anesthetic efficacy, and fetal and maternal effects.

Effects of intravaginally inserted controlled-release dinoprostone and oxytocin for labor induction on umbilical cord blood gas parameters

To compare the effects of oxytocin and dinoprostone used in labor induction on fetal blood gas parameters. This prospective randomized trial involved 108 women who completed 37 gestational weeks and who required labor induction prior to normal vaginal birth. Labor was induced in 57 women with an intravenous low dose oxytocin regimen and in 51 with intravaginal dinoprostone (PGE2). Following childbirth, umbilical artery blood gas was analyzed, with pH, pCO2, pO2, HCO3 and base excess (BE) compared in the two groups. Mean age and obstetrical data (gravidity, parity, gestational weeks and birthweight) were similar in the two groups (p>0.05). All infants had 1 and 5 minute APGAR scores ≥7. Umbilical artery blood pH was similar in the oxytocin and dinoprostone groups (7.31±0.07 vs. 7.31±0.05, p=0.780), as were the other blood gas parameters (pCO2, pO2, base excess and HCO3; p>0.05 each). Induction of labor with either oxytocin or dinoprostone in women with uncomplicated term pregnancies had no adverse effects on umbilical artery blood gas parameters.

Maternal Hyperventilation During Labor Revisited: Its Effects on Fetal Oxygenation

To investigate the relationship between maternal hyperventilation and fetal blood gas values and to estimate its possible association with fetal oxygenation, maternal transcutaneous partial pressure of carbon dioxide (tcP(CO2)) values were analyzed in association with umbilical venous P(CO2) (UVP(CO2)), umbilical venous partial pressure of oxygen (UVP(O2)), and umbilical venous oxyhemoglobin saturation (UVHbo (2)) values. Pregnant women without labor (30.7 ± 3.7 mm Hg, n = 20) showed significantly lower tcP(CO2) values compared with nonpregnant women (37.4 ± 4.0 mm Hg, n = 10). Pregnant women in the second stage of labor showed even lower tcP(CO2) values compared with pregnant women during the first stage of labor (20.8 ± 5.9 mm Hg vs 28.4 ± 5.0 mm Hg, n = 26). Maternal tcP(CO2) values had significant positive correlations with UVP(CO2) (r = .78, P < .001), UVP(O2) (r = .62, P < .001), and UVHb(O2) values (r = .59, P < .001). Maternal hyperventilation had a close relationship with lower UVP(CO2), UVP(O2), and UVHbo(2) values, which might interfere with optimal fetal cerebral oxygenation.

Activation of IGF‐2R stimulates cardiomyocyte hypertrophy in the late gestation sheep fetus

In vitro studies using rat and fetal sheep cardiomyocytes indicate that, in addition to its role as a clearance receptor, the insulin-like growth factor 2 receptor (IGF-2R) can induce cardiomyocyte hypertrophy. In the present study, we have determined the effect of specific activation of the IGF-2R in the heart of the late gestation fetus on cardiomyocyte development. Leu(27)IGF-2, an IGF-2R agonist, was infused into the fetal left circumflex coronary artery for 4 days beginning at 128.1 ± 0.4 days gestation. Ewes were humanely killed at 132.2 ± 1.2 days gestation (term, 150 days). Fetuses were delivered and hearts dissected to isolate the cardiomyocytes and to collect and snap-freeze tissue. Leu(27)IGF-2 infusion into the left circumflex coronary artery of fetal sheep increased the area of binucleated cardiomyocytes in the left, but not the right, ventricle. However, this infusion of Leu(27)IGF-2 did not change fetal weight, heart weight, blood pressure, blood gases or cardiomyocyte proliferation/binucleation. The increase in cardiomyocyte size in the Leu(27)IGF-2-infused group was associated with increased expression of proteins in the Gαs, but not the Gαq, signalling pathway. We concluded that infusion of Leu(27)IGF-2 into the left circumflex coronary artery causes cardiac IGF-2R activation in the left ventricle of the heart, and this stimulates cardiomyocyte hypertrophy in a Gαs-dependent manner.

Maternal and preterm fetal sheep responses to dexmedetomidine

BackgroundThe α2 adrenergic receptor agonist dexmedetomidine has some unique pharmacologic properties that could benefit pregnant patients (and their fetuses) when they require sedation, analgesia, and/or anesthesia during pregnancy. The purpose of the present study was to delineate maternal and fetal responses to an intravenous infusion of dexmedetomidine. MethodsThis study was conducted on surgically-recovered preterm sheep instrumented for physiologic recording and blood sampling. Maternal and fetal cardiovascular and blood gas parameters and fetal cerebral oxygenation levels were recorded before, during, and after 3h of dexmedetomidine infusion to the ewe at a rate of 1μg/kg/h. ResultsDrug infusion produced overt sedation but no apparent respiratory depression as evidenced by stable maternal arterial blood gases; fetal blood gases were also stable. The one blood parameter to change was serum glucose, By the end of the 3-h infusion, glucose increased from 49±10 to 104±33mg/dL in the ewe and from 22±3 to 48±16mg/dL in the fetus; it declined post-drug exposure but remained elevated compared to the starting levels (maternal, 63±12mg/dL, P=0.0497; and fetal, 24±4mg/dL, P=0.012). With respect to cardiovascular status, dexmedetomidine produced a decrease in maternal blood pressure and heart rate with fluctuations in uterine blood flow but had no discernable effect on fetal heart rate or mean arterial pressure. Likewise, maternal drug infusion had no effect on fetal cerebral oxygenation, as measured by in utero near-infrared spectroscopy. ConclusionsUsing a clinically-relevant dosing regimen, intravenous infusion of dexmedetomidine produced significant maternal sedation without altering fetal physiologic status. Results from this initial acute assessment support the conduct of further studies to determine if dexmedetomidine has clinical utility for sedation and pain control during pregnancy.

Nonlinear Analysis of Heart Rate Variability to Assess the Reaction of Ewe Fetuses Undergoing Fetal Cardiac Surgery

Fetal cardiac surgery (FCS) represents a challenging issue for the in utero treatment of congenital heart defects. However, FCS has still not gained the sufficient reliability for clinical practice due to an incompletely elucidated fetal stress response. For example, blood sampling can contribute to its onset, leading to fetoplacental unit dysfunction, one of the main causes of failure of the surgical procedure. In order to address this issue, the role of the autonomic control system during an experimental procedure of cardiac bypass on ewe fetuses was investigated by means of recurrence quantification analysis (RQA), a well-recognized method for the analysis of nonlinear systems. RQA was applied to time series extracted from fetal arterial pressure recordings before and after the cardiac bypass established by means of an extracorporeal circuit, including an axial blood pump, and taking advantage of the capability of the placenta to work as a natural oxygenator. Statistically significant correlations were found among RQA-based metrics and fetal blood gas data, suggesting the possibility to infer the clinical status of the fetus starting from its hemodynamic signals.This study shows the relevance of RQA as a complementary tool for the monitoring of the fetal status during cardiac bypass.

THE ENDOCRINOLOGICAL RESPONSES OF VENO-VENOUS EXTRACORPOREAL MEMBRANE OXYGENATION ON HYPOXIC FETAL LAMBS

The purpose of this study was to observe endocrinological responses of veno-arterial and veno-venous extracorporeal membrane oxygenation (V-A and V-V ECMO) to support fetal oxygenation in utero. An ECMO system with a centrifugal pump was applied to six chronically instrumented fetal lambs, at 126-134 days of gestation. Blood was obtained through a double-lumen catheter inserted into the right atrium. After oxygenation, the blood was returned through a single-lumen catheter into either the carotid artery (veno-arterial; V-A ECMO) or the right atrium (V-V ECMO). After fetal hypoxia had been experimentally produced, V-A ECMO or V-V ECMO was instituted to maintain fetal oxygenation. We compared fetal blood gases and concentrations of atrial natriuretic peptide (ANP), epinephrine and norepinephrine with both routes of ECMO. Fetal carotid artery pH did not change during hypoxemia, but decreased after instituting V-A ECMO and V-V ECMO. After instituting V-A ECMO or V-V ECMO for 30 min, oxygen partial pressure (pO2) in the fetal cranial carotid artery recovered from the hypoxic level. The ANP concentration in V-V ECMO was significantly lower than that in V-A ECMO. Fetal serum epinephrine and norepinephrine concentrations significantly increased in association with hypoxic stimulation. There was a further increase in fetal serum epinephrine concentration after instituting V-A ECMO. No significant difference in concentration was found after instituting V-V ECMO from that of after the institution of V-A ECMO. This study suggested that V-V ECMO may possibly be less invasive than V-A ECMO for fetal heart, because ANP, a cardiac distress index, was lower in V-V ECMO than in V-A ECMO.

695: Low PAPP-A levels and placental pathology: is there an association with adverse pregnancy outcome?

an association with adverse pregnancy outcome? Karen Florio, Natan Haratz, Carolyn Salafia, Samantha VanHorn, Kajal Pruthi, Andrew Smith New York Methodist Hospital Cornell/Presbyterian, OB/GYN, Brooklyn, NY, New York Methodist Hospital Cornell Presbyterian, OB/GYN, Brooklyn, NY, New York Methodist Hospital Cornell Presbyterian, OB/GYN, Pathology, Pediatrics, Brooklyn, NY, New York Methodist Hospital Cornell Presbyterian, Pediatrics, Brooklyn, NY OBJECTIVE: To evaluate perinatal outcomes in patients with low PAPP-A ( 5th percentile) between 11 and 13 6/7 weeks and the possible association with adverse placental findings. STUDY DESIGN: 150 women with singleton pregnancies who attended New York Methodist Hospital Imaging Center from 6/2007 5/2011 were included. Maternal age, gestational age, serum PAPP-A levels, serum free-BHCG levels, Nuchal translucency and CRL were recorded. Medical records were reviewed and the following parameters evaluated: 1) Maternal age, 2) BMI, 3) Race, 4) Cigarette smoking, 5) Medical history including DM, hypertension, thrombophilia, autoimmune disorders, 6) Previous obstetrical history, 7) Neonatal APGAR score, 8) Diagnosis of Pre-Eclampsia, 9) Fetal weight, 10) Fetal outcome (live vs. IUFD), 11) Fetal cord blood gases, and 12) Placental pathology. Linear regression analysis was used to compare the obstetrical outcome of these patients with age-matched controls (80) and PAPP-A above the 5th percentile. The Mann-Whitney test for nonnormally distributed variables was also utilized. RESULTS: The composite perinatal outcome (IUGR, IUFD, pre-eclampsia, spontaneous AB and pre-term labor) in our study population was significantly poorer (P 0.047) than our controls. When analyzed separately, only pre-eclampsia seemed significantly more prevalent (p 0.047) in patients with PAPP-A below the 5th percentile. Preliminary analysis of placental pathology shows a stastically significant difference in women with low PAPP-A levels and fetal thrombotic lesions (p 0.05). CONCLUSION: In this study, patients with PAPP-A levels below the 5th percentile between 11 and 13 6/7 weeks had a significantly poorer composite perinatal outcome (p 0.047). In addition, these women also had more fetal vascular lesions than the contols. We are currently analyzing various placental parameters and we speculate that other placental lesions, including inflammation, will be more prevalent in women with low PAPP-A who also experience adverse outcomes.

Blood pH and gases in fetuses in preterm labor with and without systemic inflammatory response syndrome

Objective: Fetal hypoxemia has been proposed to be one of the mechanisms of preterm labor (PTL) and delivery. This may have clinical implications since it may alter: (i) the method/frequency of fetal surveillance and (ii) the indications and duration of tocolysis to an already compromised fetus. The aim of this study was to examine whether there is a difference in the fetal blood gas analysis [pH, PaO2 and base excess (BE)] and in the prevalence of fetal acidemia and hypoxia between: (i) patients in PTL who delivered within 72 hours vs. those who delivered more than 72 hours after cordocentesis and (ii) patients with fetal inflammatory response syndrome (FIRS) vs. those without this condition. Study design: Patients admitted with PTL underwent amniocentesis and cordocentesis. Ninety women with singleton pregnancies and PTL were classified according to (i) those who delivered within 72 hours (n = 30) and after 72 hours of the cordocentesis (n = 60) and (ii) with and without FIRS. FIRS was defined as a fetal plasma concentration of IL-6 > 11 pg/mL. Fetal blood gases were determined. Acidemia and hypoxemia were defined as fetal pH and PaO2 below the 5th percentile for gestational age, respectively. For comparisons between the two study groups, ΔpH and ΔPaO2 were calculated by adjusting for gestational age (Δ = observed value – mean for gestational age). Non-parametric statistics were employed. Results: No differences in the median Δ pH (−0.026 vs. −0.016), ΔPaO2 (0.25 mmHg vs. 5.9 mmHg) or BE (−2.4 vs. −2.6 mEq/L) were found between patients with PTL who delivered within 72 hours and those who delivered 72 hours after the cordocentesis (p > 0.05 for all comparisons). Fetal plasma IL-6 concentration was determined in 63% (57/90) of fetuses and the prevalence of FIRS was 28% (16/57). There was no difference in fetal pH, PaO2 and BE between fetuses with and without FIRS (p > 0.05 for all comparisons). Moreover, there was no difference in the rate of fetal acidemia between fetuses with and without FIRS (6.3 vs. 9.8%; p > 0.05) and fetal hypoxia between fetuses with or without FIRS (12.5 vs. 19.5%; p > 0.05). Conclusions: Our data do not support a role for acute fetal hypoxemia and metabolic acidemia in the etiology of PTL and delivery.

Sex Differences in the Ovine Fetal Cortisol Response to Stress

This study tested the hypothesis that the sexually dimorphic adrenocortical response to stress is already established before birth. Chronically instrumented late gestation pregnant sheep carrying 16 male and 15 female age-matched singleton fetuses were subjected to an acute episode of hypoxic stress. Maternal and fetal blood gases, adrenocorticotrophic hormone (ACTH), and cortisol were measured. In addition, six male and six female fetuses received the ACTH analog, Synacthen, and plasma cortisol was measured. During hypoxic stress, the increment in plasma cortisol was 2-fold greater in male versus females fetuses (30.6 ± 3.2 versus 14.3 ± 2.0 ng/mL; p < 0.001) mediated, in part, by greater adrenocortical sensitivity to ACTH. The data support the hypothesis tested and show that sex-specific differences in the cortisol stress response are present before birth with the output of cortisol being much greater in male than in female fetuses.

Anti-inflammatory therapy in an ovine model of fetal hypoxia induced by single umbilical artery ligation

Perinatal morbidity and mortality are significantly higher in pregnancies complicated by chronic hypoxia and intrauterine growth restriction (IUGR). Clinically, placental insufficiency and IUGR are strongly associated with a fetoplacental inflammatory response. To explore this further, hypoxia was induced in one fetus in twin-bearing pregnant sheep (n=9) by performing single umbilical artery ligation (SUAL) at 110 days gestation. Five ewes were administered the anti-inflammatory drug sulfasalazine (SSZ) daily, beginning 24h before surgery. Fetal blood gases and inflammatory markers were examined. In both SSZ- and placebo-treated ewes, SUAL fetuses were hypoxic and growth-restricted at 1 week (P<0.05). A fetoplacental inflammatory response was observed in SUAL pregnancies, with elevated pro-inflammatory cytokines, activin A and prostaglandin E(2). SSZ did not mitigate this inflammatory response. It is concluded that SUAL induces fetal hypoxia and a fetoplacental inflammatory response and that SSZ does not improve oxygenation or reduce inflammation. Further studies to explore whether alternative anti-inflammatory treatments may improve IUGR outcomes are warranted.

652: Relationship between 5-tier color-coded framework of fetal heart rate pattern and umbilical arterial blood gas

Intrapartum management guidelines based on fetal heart rate pattern (FHR) classification was proposed by Japan Society of Obstetrics and Gynecology (JSOG) in April 2010, in which a 5-tire system was adapted instead of ACOG's 3-tier system. The aim is to validate this 5-tier classification by comparing FHR level to degree of acidemia.