Håkan Norén

Cardiotocography only versus cardiotocography plus ST analysis of fetal electrocardiogram for intrapartum fetal monitoring: a Swedish randomised controlled trial

BACKGROUND Previous studies indicate that analysis of the ST waveform of the fetal electrocardiogram provides information on the fetal response to hypoxia. We did a multicentre randomised controlled trial to test the hypothesis that intrapartum monitoring with cardiotocography combined with automatic ST-waveform analysis results in an improved perinatal outcome compared with cardiotocography alone. METHODS At three Swedish labour wards, 4966 women with term fetuses in the cephalic presentation entered the trial during labour after a clinical decision had been made to apply a fetal scalp electrode for internal cardiotocography. They were randomly assigned monitoring with cardiotocography plus ST analysis (CTG+ST group) or cardiotocography only (CTG group). The main outcome measure was rate of umbilical-artery metabolic acidosis (pH <7.05 and base deficit >12 mmol/L). Secondary outcomes included operative delivery for fetal distress. Results were first analysed according to intention to treat, and secondly after exclusion of cases with severe malformations or with inadequate monitoring. FINDINGS The CTG+ST group showed significantly lower rates of umbilical-artery metabolic acidosis than the cardiotocography group (15 of 2159 [0.7%] vs 31 of 2079 [2%], relative risk 0.47 [95% CI 0.25-0.86], p=0.02) and of operative delivery for fetal distress (193 of 2519 [8%] vs 227 of 2447 [9%], 0.83 [0.69-0.99], p=0.047) when all cases were included according to intention to treat. The differences were more pronounced after exclusion of 291 in the CTG+ST group and 283 in the CTG group with malformations or inadequate recording. INTERPRETATION Intrapartum monitoring with cardiotocography combined with automatic ST-waveform analysis increases the ability of obstetricians to identify fetal hypoxia and to intervene more appropriately, resulting in an improved perinatal outcome.

Developmental Outcome at 6.5 Years After Acidosis in Term Newborns: A Population-Based Study

OBJECTIVES: Infants who develop encephalopathy after perinatal asphyxia have an increased risk of death and adverse neurologic outcome. Conflicting results exist concerning outcome in healthy infants with metabolic acidosis at birth. The aim of the current study was to evaluate whether metabolic acidosis at birth in term infants who appear healthy is associated with long-term developmental abnormalities. METHODS: From a population-based cohort (14 687 deliveries), 78 infants were prospectively identified as having metabolic acidosis (umbilical artery pH < 7.05 and base deficit in the extracellular fluid >12.0 mmol/L). Two matched controls per case were selected. The child health and school health care records were scrutinized for developmental abnormalities. RESULTS: Outcome measures at 6.5 years of age for 227 of 234 children (97%) were obtained. No differences were found concerning neurologic or behavioral problems in need of referral action or neurodevelopmental diagnosis in comparison of control children with acidotic children who had appeared healthy at birth, ie, had not required special neonatal care or had no signs of encephalopathy. CONCLUSIONS: Infants born with cord metabolic acidosis and who appear well do not have an increased risk for neurologic or behavioral problems in need of referral actions or special teaching approaches at the age of 6.5 years.

ST analysis of the fetal electrocardiogram during labor: Nordic observational multicenter study

Objective: To assess the diagnostic power of cardiotocography (CTG) plus the ST interval of the electrocardiogram (ECG) clinical guidelines with combined fetal heart rate and ST waveform analysis of the fetal ECG recorded during labor, to identify an adverse labor outcome (neonatal neurological symptoms and/or metabolic acidosis). Study design: An observational, multicenter study was undertaken in 12 Nordic labor wards. A total of 573 women in labor were monitored using a prototype of the STAN® S 21 recorder with fetal ECG data and computerized ST analysis. Results: Fifteen cases of intrapartum fetal hypoxia identified from neurological neonatal symptoms and/or cord artery pH < 7.05 with base deficit in extracellular fluid > 12.0 mmol/l were recorded. All these cases were identified by CTG + ST clinical guidelines. Five developed neonatal symptoms and had ECG abnormalities during the first stage of labor and, of the remaining ten, eight showed ST changes during active pushing in the second stage. Another eight cases had acidemia only and normal neonatal outcome. Seven of these displayed CTG + ST abnormalities. The high sensitivity of CTG + ST to predict fetal acidosis was associated with a marked increase in positive predictive values compared with conventional CTG. Conclusion: The STAN clinical guidelines identify fetuses at risk of intrapartum asphyxia.

Fetal scalp pH and ST analysis of the fetal ECG as an adjunct to CTG. A multi-center, observational study

Abstract Objective: To evaluate the relationships between scalp-pH and CTG plus ST waveform analysis of the fetal ECG (STAN) clinical guidelines as indicators of intrapartum hypoxia in term fetuses born with cord artery acidemia. Study design: Data from 6999 term deliveries monitored by the STAN® S 21 as part of an EU multi-center study on clinical implementation of the STAN methodology for intrapartum fetal surveillance were analyzed. We identified 911 cases where a scalp-pH was obtained, including 53 cases with cord artery acidemia (pH < 7.06). Lag times between ST events and scalp-pH and time to delivery were related to cord artery metabolic and respiratory acidosis and neonatal outcome. Results: 43 fetuses were identified by CTG plus ST as being in need of intervention 31 (25–46) minutes before delivery (median, 95% Cl). In five, no indications were given and in another five there were inadequate data. Fifteen cases with metabolic acidosis required special neonatal care, all 14 cases adequately monitored on STAN had indications to intervene for 19 minutes or more. In 30 adequately recorded cases, fetal blood sampling (FBS) was obtained within the last hour of labor. In 22 cases, FBS was obtained 13 (7–24) minutes after STAN guidelines had indicated abnormality and in eight no ST changes had occurred at time of FBS. The corresponding FBS data were pH 7.10 (7.01–7.15) and pH 7.21 (7.08–7.31), respectively, P = 0.01. In cases of metabolic acidosis, scalp-pH fell 0.01 units per minute after a baseline T/QRS rise was recorded during the second stage of labor. Apart from one newborn that died at 2 h from E. Coli septicemia, none of the neonates were affected neurologically. Conclusion: Cardiotocography plus ST analysis provides accurate information about intrapartum hypoxia similar to that obtained by scalp-pH.

Reduced prevalence of metabolic acidosis at birth: an analysis of established STAN usage in the total population of deliveries in a Swedish district hospital

OBJECTIVE The purpose of this study was to investigate quality-of-care improvements after the introduction of ST waveform analysis as an adjunct to standard cardiotocography (CTG). STUDY DESIGN This was a prospective clinical study that was conducted over 7 years. Four yearly cohorts of 12,832 term pregnancies were part of a detailed analysis. Cord blood metabolic acidosis and neonatal outcome were main outcome measures. RESULTS The STAN (S31 Fetal Heart Monitor; Neoventa Medical AB, Mölndal, Sweden) usage rate increased from 26 to 69%. The cord metabolic acidosis rate was reduced from 0.72 to 0.06%. This 91.7% improvement was associated with a significant reduction in the number of cases with a prolonged response time, calculated as the time from CTG + ST indications to intervene until delivery and an ability of the staff to identify and act on preterminal and unstable fetal heart rate patterns at the onset of a recording. CONCLUSION Our data indicate a paradigm shift in the outcome of delivery related to a high rate of CTG + ST usage and the application of structured CTG analysis.

A new tool for the validation of umbilical cord acid–base data

Please cite this paper as: Kro G, Yli B, Rasmussen S, Norèn H, Amer‐Wåhlin I, Didrik Saugstad O, Stray‐Pedersen B, Rosén K. A new tool for the validation of umbilical cord acid–base data. BJOG 2010;117:1544–1552.

Fetal scalp ph and ST analysis of the fetal ECG as an adjunct to cardiotocography to predict fetal acidosis in labor : A multi-center, case controlled study

Abstract Objective: To assess the relationship between scalp pH (FBS) and ST analysis in situations of acidosis with special emphasis on the timing of cardiotocography (CTG), FBS and ST changes during labor. Study design: From a European Union multicenter study on clinical implementation of the STAN methodology, 911 cases were identified where a scalp-pH had been obtained. In 53 cases, marked cord artery acidosis was found (cord artery pH<7.06) and 44 cases showed moderate acidemia at birth (pH 7.06–7.09). Comparisons were made with 97 control cases (pH≥7.20). Results: Of those cases with FHR+ST events recorded within 16 min of delivery, 61% (17/28) had a cord artery pH≥7.20. The corresponding figure for cases where STAN indications occurred for more than 16 min was 19% (13/69) (OR 6.66, 2.53–17.55, P<0.001). Out of the 121 cases with an abnormal CTG, 84 (69%) showed a cord artery pH of <7.10. STAN indicated abnormality in 83% (70 out of 84). The corresponding figure for scalp pH<7.20 was 43% (36/84). In the case of CTG changes at the start of an adequate recording STAN guidelines provided information on developing acidosis in all cases but one (16 out of 17) in the marked acidosis group. STAN guidelines indicated abnormality prior to an abnormal FBS in 14 out of 17 cases. The median duration between STAN indications to intervention and an abnormal FBS was 29 (95% CI 11–74) min. Conclusions: ST analysis, as an adjunct to CTG, identifies adverse fetal conditions during labor similar to that of FBS but on a more consistent basis. The timing of CTG+ST changes relates to the level of acidosis at birth.

Real-time PCR-assay in the delivery suite for determination of group B streptococcal colonization in a setting with risk-based antibiotic prophylaxis

Abstract Objective: Intrapartum antibiotic prophylaxis (IAP) reduces the incidence of neonatal early onset group B streptococcal infections. The present study investigated if an automated PCR-assay, used bedside by the labor ward personnel was manageable and could decrease the use of IAP in a setting with a risk-based IAP strategy. Methods: The study comprises two phases. Phase 1 was a multicenter, randomized, controlled trial. Women with selected risk-factors were allocated either to PCR-IAP (prophylaxis given if positive or indeterminate) or IAP. A vaginal/rectal swab and superficial swabs from the neonate for conventional culture were also obtained. Phase 2 was non-randomized, assessing an improved version of the assay. Results: Phase 1 included 112 women in the PCR-IAP group and 117 in the IAP group. Excluding indeterminate results, the assay showed a sensitivity of 89% and a specificity of 90%. In 44 % of the PCR assays the result was indeterminate. The use of IAP was lower in the PCR group (53 versus 92%). Phase 2 included 94 women. The proportion of indeterminate results was reduced (15%). The GBS colonization rate was 31%. Conclusion: The PCR assay, in the hands of labor ward personnel, can be useful for selection of women to which IAP should be offered.

How does the duration of active pushing in labor affect neonatal outcomes

Abstract Aim: To assess the effect of time of active pushing (TAP) on neonatal outcome. Materials and methods: The study population (n=36,432) was taken from a Swedish randomized control trial on intrapartum monitoring, a European Union fetal electrocardiogram trial, and from Mölndal Hospital. After validation of acid-base samples and TAP, 22,812 cases were accepted for analysis. Results: The median active TAP was 36 min for P0 and 13 min for P≥1 (P<0.001). After adjustments for parity, epidural, labor induction, birth weight, and gender, pushing for 15–29 min (n=6589) relative to pushing for <15 min (n=7264) increased the OR of a cord artery pH of <7.00 to 3.20 (95% CI 1.7–6.0), and that of a base deficit in extracellular fluid of >12 mmol/L to 3.5 (95% CI 1.3–9.0). The group with a cord artery pH of <7.00 had a longer TAP than the group with pH≥7.00: median (5th–95th percentile), 38 (9–107) min vs. 23 (5–87) min, P<0.001. The probability of a spontaneous vaginal delivery decreased significantly with every subsequent increase of 30 min in TAP (P<0.05). Conclusion: The risks of severe acidemia, metabolic acidosis, and deteriorated neonatal outcome gradually increased with the length of TAP (>15 min), while the probability of a spontaneous vaginal delivery decreased with the duration of pushing. We suggest active physiological evaluation of the labor progress together with continuous electronic fetal monitoring during pushing irrespective of guideline thresholds.

Endothelin—a potent constrictor of small myometrial arteries of term pregnant women

This study was performed to evaluate the in vitro effects of a new polypeptide, endothelin‐1 (ET‐1) on small intramyometrial vessels in comparison with the action of noradrenalin (NA). In connection with cesarean section, myometrial biopsies were obtained and small arteries (100–500 um in diameter) were excised. Cylindrical segments of these vessels were used for registration of contractile activity after administration of ET‐1 and NA. ET produced vasoconstriction and was approximately three times as powerful and 70‐fold as potent as NA. It is suggested that ET may be involved in the regulation of human utero‐placental blood flow.