Fetal pH Research Articles

Maternal and fetal Acid-base chemistry: a major determinant of perinatal outcome.

Very small changes in pH may significantly affect the function of various fetal organ systems, such as the central nervous system, and the cardiovascular system with associated fetal distress and poor Apgar score. Review of existing data on maternal-fetal acid-base balance in pregnancy highlight the factors that are associated with derangements of the acid-base status and the impact of the derangements on fetal outcome. Extensive search of electronic databases and manual search of journals for relevant literature on maternal and fetal acid chemistry, clinical studies and case studies were undertaken. There is a substantial reduction in the partial pressure of carbon dioxide (pCO2) in pregnancy. Adequate buffering prevents significant changes in maternal arterial pH. Normal fetal metabolism results in the production of acids which are buffered to maintain extracellular pH within a critical range. Fetal hypoxia can occur when maternal oxygenation is compromised, maternal perfusion of the placenta is reduced, or delivery of oxygenated blood from the placenta to the fetus is impeded. When adequate fetal oxygenation does not occur, metabolisms proceed along with an anaerobic pathway with production of organic acids, such as lactic acid. Accumulation of lactic acid can deplete the buffer system and result in metabolic acidosis with associated low fetal pH, fetal distress and poor Apgar score. There is a significant reduction in pCO2 in pregnancy. This change, however, does not result in a corresponding significant reduction in maternal arterial pH, because of adequate buffering. Very small changes in pH may cause significant derangement in fetal function and outcome.

Accuracy of a hand-held lactate meter in measuring umbilical cord blood lactate at all lactate levels

Objective: Fetal scalp lactate has largely replaced pH analysis to assess intrapartum hypoxia. Many obstetrics units use hand-held lactate meters to measure umbilical blood because of its affordability and ease of use. We sought to investigate the agreement of Lactate ProTM with a reference method blood gas analyser and to determine its usefulness with a recommended cutoff value of 4.8 mmol/L. Methods: Prospective study carried out at a tertiary institution where 237 arterial and 233 venous samples from umbilical cords of 16 elective caesarean and 285 emergency deliveries were measured using Lactate ProTM and ABL735 Sesries Acid-Base analyser. Limits of agreement were analysed using Bland-Altman plots. Results: Lactate ProTM differentiated fewer deliveries as “high risk” (≥4.8 mmol/L) and more as “low risk” (TM) were –1.46 - 0.97 mmol/L for arterial lactate levels arterial lactate levels ≥ 4.8 mmol/L. Conclusion: There was a poorer agreement between the two devices at higher lactate values. Lactate ProTM underestimates by up to 3.2 mmol/L; a 4.8 mmol/L reading may actually signify a lactate level of 8.0 mmol/L, indicating severe metabolic acidosis. We caution the use of this device in assessing fetal lactate levels.

Experience of fetal scalp blood sampling during labor

Fetal scalp blood sampling (FBS) is often claimed to be painful for women in labor and difficult for obstetricians to perform. Our aim was to assess women's experience of pain during FBS and obstetricians' experience of difficulty in performing the test. At a tertiary center in Sweden, a questionnaire with answers on a 10-point scale was completed by 51 women and the obstetricians performing the test. Women's experience of pain had a median of 3.5. FBS was well tolerated in women who had epidural analgesia but might be associated with pain in women without. Higher maternal body mass index and less cervical dilation were associated with higher pain ratings. Obstetricians did not generally experience scalp sampling as difficult to perform (median score 3.0). However, the sampling procedure can be more complicated in situations with higher maternal body mass index, less cervical dilation, and a higher station of the fetal head.

Correlation of Amniotic Fluid Index with Perinatal Outcome

We aimed to evaluate the predictive value of amniotic fluid index (AFI) (<5) for adverse perinatal outcome in terms of cesarean section for fetal distress, birth weight, meconium staining, Apgar scores, and cord pH at birth. This was a prospective study of 200 antenatal women booked at Ram Manohar Lohia (RML) Hospital during the years 2009-2011 with gestational age between 34 and 41weeks. The women's history, clinical examination recorded, and AFI were measured and the perinatal outcome was compared between two groups, i.e., AFI<5 and >5. The cesarean section rate for fetal distress and low birth weight babies, <2.5kg, was higher in patients with oligohydramnios (p=0.048, 0.001, respectively). There was no significant difference in meconium staining, Apgar score at 5min <7, and cord pH at birth between the two groups (p=0.881, 0.884, 0.764, respectively). Oligohydramnios has a significant correlation with cesarean section for fetal distress and low birth weight babies.

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.

Cord blood B-type natriuretic peptide levels in placental insufficiency: correlation with fetal Doppler and pH at birth

ObjectiveTo examine the correlation of cardiac B-type natriuretic peptide (BNP) concentrations in umbilical cord blood at birth with fetal Doppler parameters and pH at birth. Study designProspective cross-sectional study with the following inclusion criteria: women with a singleton pregnancy, placental insufficiency characterized by increased pulsatility index (PI) of the umbilical artery (UA), intact membranes, and absence of fetal abnormalities. The exclusion criteria kept out cases of newborns with postnatal diagnosis of abnormality and cases in which the blood analysis was not performed. The Doppler parameters used were the UA PI, middle cerebral artery (MCA) PI, cerebroplacental ratio (CPR), and ductus venosus (DV) PI for veins (PIV), all converted into zeta scores. Blood samples were obtained from the umbilical cord immediately after delivery to measure the pH of the UA and the BNP. ResultsThirty-two pregnancies with placental insufficiency were included, 21 (65%) with positive diastolic flow and 11 (35%) with absent or reversed end diastolic flow in the UA. The concentration of BNP correlated significantly with the UA PI z-score (rho=0.43, P=0.016), the CPR z-score (rho=−0.35, P=0.048), the DV PIV z-score (rho=0.61, P<0.001), pH at birth (rho=−0.39, P=0.031), and gestational age (rho=−0.51, P=0.003). In the multiple regression analysis, antenatal parameters were included; the DV PIV z-score (P=0.008) was found to be an independent parameter correlating with BNP at birth. Correlation between BNP and the DV PIV z-score was borne out by the regression equation Log[BNP]=2.34+0.13*DV (F=18.8, P<0.001). Correlation between BNP and pH at birth was confirmed by the regression equation Log[BNP]=21.36–2.62*pH (F=7.69, P=0.01). ConclusionThe results suggest that fetal cardiac dysfunction identified by BNP concentrations at birth correlated independently with changes in DV PIV and correlated negatively with pH values at birth.

The Association of Maternal Obesity With Fetal pH and Base Deficit at Cesarean Delivery

To evaluate the association between maternal body mass index (BMI) and umbilical cord acid-base status at the time of cesarean delivery. We conducted a retrospective multicenter cohort study using data from the Cesarean Section Registry of the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. Women were included if they delivered a live, nonanomalous singleton at 37-41 weeks of gestation by prelabor cesarean under spinal anesthesia. We excluded women with diagnoses that might be associated with uteroplacental insufficiency. Body mass index at delivery was examined both as a continuous and categorical exposure, and acid-base status was based on cord arterial pH and base deficit. There were 5,742 mother-neonate pairs who met criteria for analysis. Among possible confounders (including sociodemographic variables, number of previous uterine incisions, diabetes, hematocrit, neonatal gender, and birth weight), African American race, birth weight, parity, and smoking status were significantly associated with both BMI and acid-base parameters. Adjusted for those four factors, with increasing BMI category (less than 25, 25-29.9, 30-34.9, 35-39.9, and 40 or higher), mean pH decreased from 7.25 to 7.22 (P<.001), proportion with pH less than 7.1 increased from 3.5% to 7.7% (P=.011), mean base deficit increased from 4.01 mmol/L to 4.83 mmol/L (P=.030), and proportion with base deficit of 12 mmol/L or more increased from 0.6% to 4.7% (P=.003). When BMI was analyzed continuously and adjusted for these confounders, for every 10-unit increase in BMI, cord arterial pH decreased by 0.01 (P<.001) and base deficit increased by 0.26 mmol/L (P=.005). For women undergoing nonemergent prelabor cesarean delivery under spinal anesthesia, fetal pH declines and base deficit rises as maternal BMI increases. II.

Do spectral bands of fetal heart rate variability associate with concomitant fetal scalp pH?

BackgroundObjective information on specific fetal heart rate (FHR) parameters would be advantageous when assessing fetal responses to hypoxia. Small, visually undetectable changes in FHR variability can be quantified by power spectral analysis of FHR variability. AimsTo investigate the effect of intrapartum hypoxia and acidemia on spectral powers of FHR variability. Study designThis is a retrospective observational clinical study with data from an EU multicenter project. SubjectsWe had 462 fetuses with a normal pH-value (pH>7.20; controls) in fetal scalp blood sample (FBS) and 81 fetuses with a low scalp pH-value (≤7.20; low-FBS pH-fetuses). The low-FBS pH-fetuses were further divided into two subgroups according to the degree of acidemia: fetuses with FBS pH7.11–7.20 (n=58) and fetuses with FBS pH ≤7.10 (n=23). Outcome measuresSpectral powers of FHR variability in relation to the concomitant FBS pH-value. ResultsFetuses with FBS pH ≤7.20 had increased spectral powers of FHR variability compared with controls (2.49AU vs. 2.23AU; p=0.038). However, the subgroup of most affected fetuses (those with FBS pH ≤7.10) had significantly lower FHR variability spectral powers when compared to fetuses with FBS pH7.11–7.20. ConclusionsThis study shows that spectral powers of FHR variability change as a fetus becomes hypoxic, and that spectral powers decrease with deepening fetal acidemia.

Factors Associated with the Recent Increasing Cesarean Delivery Rate at a Japanese Perinatal Center

Objective. We examined which specific factors contributed to the increase in Cesarean delivery rate at our hospital over a 10-year period. Methods. From January 2002 to December 2012, data on the Japanese singleton deliveries at ≥22-week gestation managed at Japanese Red Cross Katsushika Maternity Hospital were collected. Potential factors associated with the increasing Cesarean delivery rate were selected according to previous studies. In this study, the incidences of intrauterine fetal demise, umbilical artery pH <7.1, and severe perineal laceration were calculated for each year. Results. The Cesarean delivery rate at our institution increased significantly during the study period (17.3% in 2002 versus 23.4% in 2012, P < 0.01). During the study period, the Cesarean delivery rates in the cases of nulliparity, preterm delivery, low birth weight (<2,500 g), previous Cesarean deliveries and breech presentation were increased significantly. The incidence of intrauterine fetal demise and low umbilical artery pH was significantly decreased, and a negative correlation was found between the Cesarean delivery rate and the incidence of low umbilical artery pH for each year (r = −0.92, P < 0.01). Conclusion. At our institute, the neonatal outcomes seemed to be improved associated with the increased Cesarean delivery rate between 2002 and 2012.

Repérage de l’asphyxie au cours du travail

Intrapartum asphyxia is defined as metabolic acidemia measured at birth with pH < 7.00 and base deficit ≥ 12 mmol/L. It is today established that the proportion of cerebral palsy associated with intrapartum hypoxia-ischemia is about 14.5%. Intrapartum asphyxia is screened in France by the continuous fetal heart rate (FHR) monitoring which presents a good sensitivity for its detection. His low specificity justifies the use of second line methods to reduce the increase of cesarean deliveries associated with the use of continuous FHR monitoring. Fetal scalp pH and lactate measurements are still the reference method. The conclusions of the last meta-analysis on the RCTs of the use of the fetal electrocardiogram (STAN®) appear to be disappointing, because no differences were found in the rates of metabolic acidosis and the rates of cesarean deliveries. Intrapartum asphyxia’s diagnostic can be made by analysis of the acidbase status on the cord arterial blood. Therefore, it should be systematically performed after every births.

Short-term neonatal outcome in diabetic versus non-diabetic pregnancies complicated by non-reassuring foetal heart rate tracings

Objective: Analysis of the impact of non-reassuring foetal heart rate patterns (FHR) and suspected foetal distress during active labour on the neonatal outcome in diabetic compared to non-diabetic mothers.Methods: Retrospective case–control study comparing the short-term neonatal outcome including Apgar score at 5 min, and arterial/venous umbilical cord blood pH of 57 deliveries of women with different types of diabetes and 114 healthy controls. Patients were selected out of all deliveries with suspected foetal distress during active labour and performed foetal scalp pH samplings (n = 590) at the Medical University of Graz, Austria, during 2008–2009.Results: Arterial pH was significantly lower in the diabetic group (7.215 versus 7.250, p = 0.007). Apgar scores ( > 8) at 5 min were similar in both groups (96.5% versus 95.6%, p = 0.566). The percentage of cases with foetal scalp blood pH <7.25 was higher in the diabetes group, but did not reach statistical significance (14.1% versus 7.1%, p = 0.166).Conclusions: Newborns of women with gestational and type 1 diabetes and non-reassuring FHR tracing have significantly lower arterial cord blood pH values without consequences on neonatal postpartum adaptation. Special attention to pathological changes in FHR patterns and to the more rapid decline in foetal pH during periods of foetal distress may be warranted in women with gestational and pre-conceptional diabetes during active labour. More frequent foetal scalp pH testing to rule out clinically relevant foetal acidosis needs to be discussed.

Neural signature of cerebral activity of the fetal cholinergic anti‐inflammatory pathway derived from heart rate variability

Fetal cholinergic anti‐inflammatory pathway (CAP) activity parallels changes in fetal heart rate variability (fHRV) in response to acidemia or inflammation. We hypothesized that 1) a multi‐domain fHRV measures approach will detect CAP activation early and 2) the degree of CAP activation will reflect the level of cerebral inflammation independent of the type of stimulus ‐ spontaneous hypoxia (n=5, arterial O2sat&lt;50%), LPS (n=6) or control (n=9).Chronically‐instrumented near term fetal sheep underwent increasingly intense umbilical cord occlusions until fetal pH&lt;7.00 (~3–4 h). FHRV measures Skewness, Assymetry Index (AsymI), RMSSD, Sample Entropy (SampEn) and Fuzzy Entropy (FuzEn) were calculated continuously using the automated and standardized Continuous Individualized Multiorgan Variability Analysis, and correlated to microglia (MG) counts in specific brain regions. RMSSD and FuzEn increased and SampEn decreased early. Measures of fHRV symmetry did not change with worsening acidemia but correlated to MG counts, with CA1 MG counts correlating only to AsymI. SampEn correlated most often to MG counts in all regions except the DG, which correlated to FuzEn, Skewness and RMSSD. The spatiotemporal pattern of correlation to fHRV measures of different property domains provides a neural signature of cerebral CAP activity.Funding: Women's Development Council, FRSQ, CIHR, MITACS/NeuroDevNet

PL.60 Consequences of Failed Instrumental Deliveries- How Bad is It?

BackgroundUnsuccessful instrumental delivery (ID) is typically associated with increased risks of adverse outcomes. We aimed to investigate the fetal and maternal consequences of failed instrumental deliveries in our unit.MethodsData was...

True umbilical cord knot and obstetric outcome

ObjectiveTo identify risk factors for true umbilical cord knot and to evaluate its association with fetal death, premature birth, low birth weight, small-for-gestational-age (SGA) infants, low Apgar score at 1 and 5minutes, fetal venous pH of 7.15 or lower, and need for neonatal intensive care in singleton pregnancies. MethodsThe total population of women who delivered at Kuopio University Hospital, Kuopio, Finland, between January 2000 and August 2012 was reviewed. Risk factors for umbilical cord knot and its association with adverse pregnancy outcome were evaluated separately among women with and without true cord knot via logistic regression analysis. ResultsOverall, 340 (1.2%) of 27 537 singleton pregnancies were affected by umbilical cord knot, with increased incidence associated with advanced maternal age, multiparity, previous spontaneous abortion, polyhydramnios, and diabetes mellitus. Umbilical cord knot was associated with a 1.58-, 8.08-, 3.90-, 3.17-, 1.67-, and 2.00-fold increased risk of neonatal intensive care, fetal death, premature birth, SGA infants, and low Apgar score at 1 and 5minutes, respectively. ConclusionTrue umbilical cord knot is relatively common and is associated with increased incidence of SGA infants, premature birth, need for neonatal intensive care, and fetal death.

Corrélation entre prélèvements au scalp fœtal et prélèvements artériels au cordon

The objective was to evaluate the correlation between fetal scalp base excess (BE) and umbilical cord BE. Respective value of fetal scalp pH, BE and lactate for the prediction of neonatal metabolic acidosis were also evaluated. A retrospective monocentric study was conducted in a French tertiary care academic maternity. All the patients who had a fetal scalp sampling during labor in 2010, less than 90 minutes before delivery were included. Fetal heart rate abnormalities (FHRA) were classified by degree of severity, according to the French guidelines. The differences between fetal scalp samples and umbilical cord samples over time and in relation with the type of FHRA were analyzed for pH and BE. The differences between fetal scalp pH and cord pH over time and in relation with scalp BE were analyzed. The correlation between fetal scalp samples and cord samples for pH, BE and lactate was estimated. Receiver operating characteristics (ROC) curves for fetal scalp pH, lactate and BE to predict umbilical cord pH under 7.20 were calculated. Seventy-one cases were included. The difference between fetal scalp sample and cord sample was lower when the sample was made closest to delivery both for pH and BE. The gravity of FHRA was not predictive of a faster decrease of pH or BE over time. The correlation was significant for pH (r=0.23, p=0.03) between scalp samples and cord samples, as for BE (r=0.49, p=0.001) and lactate (r=0.52, p=0.001). The ROC curves for pH, BE and lactate displayed a similar pattern. Fetal scalp and umbilical cord samples, for pH, BE and lactate were significantly correlated but their respective predictive value for cord pH less or equal to 7.20 was poor.

Maternal and Foetal Cardiovascular Effects of the Anaesthetic Alfaxalone in 2‐Hydroxypropyl‐β‐cyclodextrin in the Pregnant Ewe

The objective of this study was to determine the pharmacodynamics effects of the anaesthetic alfaxalone in 2-hydroxypropyl-β-cyclodextrin in pregnant sheep after the intravenous injection of a 2 mg/kg weight dose. Six pregnant Ripollesa sheep, weighing 47.1 ± 4.4 kg, were used. Twenty-four hours after instrumentation, sheep were anaesthetized with intravenous alfaxalone in cyclodextrin. Time to standing from anaesthesia was 30.0 ± 10.81 min. Foetal heart rate increased significantly during the first 5 min after alfaxalone administration. Significant differences were observed in maternal diastolic arterial blood pressure between minute 10 and minutes 90, 120, 150, 180, 210, and 240. Significant differences were observed for foetal systolic arterial blood pressure between 5 and 30 min after alfaxalone administration. Significant differences in foetal pH were detected during the entire study period, whereas maternal pH returned to baseline values by 60 min after alfaxalone administration. The present study indicated that alfaxalone in 2-hydroxypropyl-β-cyclodextrin administered as an intravenous bolus at 2 mg/kg body weight produced minimal adverse effects and an uneventful recovery from anaesthesia in pregnant sheep and their foetus.

A comparison of three vasopressors for tight control of maternal blood pressure during cesarean section under spinal anesthesia: Effect on maternal and fetal outcome

Purpose:Maintaining systolic blood pressure (SBP) at 100% of baseline is best for fetal and maternal outcome. We hypothesized that irrespective of the vasopressor used, maintaining SBP at 100% of baseline with phenylephrine (P), metaraminol (M), or ephedrine (E) will produce the best fetal pH after cesarean section (LSCS) under subarachnoid block (SAB).Materials and Methods:Ninety ASA 1 women scheduled for elective LSCS were randomly allocated to receive P, M, or E. SAB was established with patient in left lateral position using 2.5 cc of 0.5% hyperbaric bupivacaine. Immediately following SAB, patients received a bolus of the study drug (E = 5 mg, M = 0.5 mg, P = 30 mcg) followed by infusion (E = 2.5 mg/min, M = 0.25 mg/min, P = 15 mcg/min) to maintain SBP at 100% baseline. Umbilical blood gases, maternal hemodynamic parameters, and complications were recorded.Results:The umbilical pH was comparable in all the three groups (P > 0.05). The mean SBP from spinal block until delivery was similar over time for all the three groups. The incidence of reactive hypertension was more in group M (P < 0.05) than in group E and group P. Total drug consumption to meet target blood pressure till delivery was 39.3 ± 14.6 mg in group E, 1.7 ± 0.9 mg in group M, and 283.6 ± 99.8 mcg in group P. The incidence of nausea and vomiting was comparable in the three groups.Conclusion:All the three vasopressors were equally effective in maintaining maternal blood pressure as well as umbilical pH during spinal anesthesia for cesarean section without any detrimental effects on fetal and maternal outcome.

Justified indicators for caesarean section in fetal distress

Introduction. The number of caesarean sections (CSs) carried out is rising worldwide, with one of the main fetal indicators for this method of delivery being fetal distress. In our department, the rate is reported to be particularly high compared with the literature. Our decision to perform a CS delivery during labour is based only on the cardiotocograph (CTG) recording, and so the aim of this study was to carry out an audit of CSs in fetal distress with a view to analysing this criterion, and to link the CTG findings that diagnose fetal distress to fetal outcome in order to assess the accuracy of the diagnosis. Methods. This is a retrospective and descriptive study of cases, using files, delivery book and electronic medical records which were collected over a period of 6 months. Some relevant clinical data were collected and used to measure clinical distress in the fetus. Some of the results relating to CS incidence and CTG recording have been compared with the literature. The major factors leading to emergency CSs were identified. Decision to delivery time and neonatal outcome were assessed based on Apgar score, cord pH and neonatal intensive care admission. Results. There were 1890 deliveries during the study period, i.e. 1 June 2011 to 31 December 2011. Of these, 101 women underwent CSs due to fetal distress, with 90 (17.4% of total CSs) included in the study. The remaining 11 women were excluded as they did not meet study criteria. The main indicators for CSs were CTG-recording abnormalities and meconium-stained liquor. One of the major points to emerge was that despite women having been taken for an emergency CS as a result of fetal distress, analysis of the fetal outcome showed that not one of the newborns had low Apgar score (< 7) at 5 minutes. Conclusion. The high rate of CSs for fetal distress in our department is probably due to a lack of other surveillance methods such as fetal scalp blood sampling and integrated CTG recording and fetal electrocardiography, but it is also symptomatic of the fear of medicolegal issues.

Progress of Perinatal Medicine in Spain

The purpose of this article is to analyze the evolution and progress made in Perinatal Medicine in Spain over the past 40 years. Advances made in the range of technologies used in Perinatal Medicine and their implementation are described: ultrasonography, biophysical and biochemical monitorization (cardiotocography, fetal pH testing, etc.), prenatal diagnosis, amnioscopy, etc. Therapeutic approaches are also discussed: therapeutic uterine activity, fetal intrauterine treatment (medical and surgical), analgo-anesthesia in obstetrics, obstetric surgical technique, conducted when the threat of premature delivery exists, etc. The individuals who made these different advances are cited throughout the text, as are the contributions of Spanish Perinatologists to these areas. For many years Spanish Perinatology was influenced by the so-called “Montevideo School” created by Caldeyro-Barcia. The specialty later embraced all the innovations contributed by European and American investigation groups. Perinatal results have improved progressively over the years. Spanish levels of maternal and perinatal death are now amongst the lowest in Europe. Not only has the existence of a quality National Health System contributed to these improvements but the dynamism developed in perinatal medicine at some of the country’s major hospitals as well.

The reliability of foetal blood sampling as a test of foetal acidosis in labour

To establish whether foetal blood sampling for pH is a reliable test of foetal acidosis in labour by comparing paired foetal blood samples taken at a single procedure. We conducted a prospective study assessing 293 consecutive attempts at foetal blood sampling in labour over a four month period from February to May 2012. A total of 100 paired samples were suitable for analysis. We compared the consistency of pH results of paired foetal blood samples, evaluated cases where inconsistent results would result in conflicting clinical decisions, and explored factors associated with discordant results. There was a statistically significant difference between the mean pH of the two samples: 7.297 (SD 0.065) versus 7.315 (SD 0.059), p<0.0005. Of the 100 paired samples, 43 had a difference greater than the laboratory acceptable maximum analytical difference of 0.038. There was discordance between the samples in 16 cases with results crossing a decision threshold, and in 11 cases (69%) delivery was by emergency caesarean section. Inconsistent results were not associated with specific clinical factors and occurred more often with senior operators. Foetal blood sampling is considered by many as the gold standard in assessing intrapartum foetal wellbeing. We have demonstrated inconsistency of paired foetal blood pH results which suggests that foetal blood sampling should not be considered infallible.