Intrapartum fetal asphyxia: study of umbilical cord blood lactate in relation to fetal heart rate patterns

Purposes

To correlate between umbilical artery cord blood lactate and acid–base status with intrapartum fetal heart rate monitoring, and to measure the reliability of umbilical cord blood lactate for prediction of early neonatal outcome.

Methods

Sixty-six participants with intrapartum abnormal fetal heart rate monitoring and 60 participants with normal intrapartum recordings were recruited. The abnormal recordings included late onset, atypical variable and simple variable decelerations. After delivery, the arterial cord blood lactate, pH, actual base excess (ABE), and Apgar score were measured in all participants.

Results

There was significant inverse correlation between cord lactate and pH and ABE in all participants (correlation coefficient = ?0.7, p < 0.0001). The cord lactate was significantly higher in the late onset and atypical variable decelerations groups compared to control (p < 0.0001). There was no significant correlation between the Apgar score and blood lactate in all groups; however, the sensitivity and specificity of cord lactate to predict low score at 5 min were higher in comparison to cord pH.

Conclusions

Umbilical cord blood lactate is a reliable marker for intrapartum fetal asphyxia compared to cord acid–base status with better prediction for newborns with low Apgar score.     

脐带因素与胎儿生长发育及新生儿体重的关系

目的探讨应用脐带多项指标评估胎儿宫内生长发育状况及新生儿体重的临床价值。方法2 0 0 0年2月至2 0 0 2年6月间河北医科大学附属第四医院产前经多普勒超声测量脐带、脐动脉、脐静脉直径,脐动脉血流参数,脐静脉流速,并与胎龄比较。产后测量脐带长度、直径、脐带扭转周数,脐血生长激素(GH)、微量元素含量。根据正常新生儿体重分为大、中、小3组,分别与所测指标进行比较。结果脐带、脐动脉、脐静脉直径随胎龄生长而持续增长,并与新生儿体重呈正相关。脐动脉血流参数随胎龄增长而逐渐降低。胎儿脐静脉血流量孕4 0周时为80mL/ (min·kg)。脐带长度与脐带直径、胎儿体重无关。脐带长度与扭转周数有关,与脐带绕颈绕身有关。脐血中GH含量与新生儿体重有关,微量元素与新生儿体重无关。结论产前应用脐带多项指标评估胎儿宫内生长发育状况及体重有临床价值。     

Divergence of estimated fetal weight and birth weight in singleton fetuses

Objective: To evaluate differences in distribution of estimated fetal weight (EFW) and birth weight (BW) of ongoing fetuses and neonates of the same gestational age.

Methods: Reference curves for EFW (Hadlock BPD-HC-AC-FL formula, N?=?1191) and BW (N?=?1036) in singleton pregnancies from 24⁺⁰ to 40⁺⁶ gestational weeks were calculated. Multiple pregnancies, fetuses with major or multiple abnormalities or syndromes and iatrogenic preterm deliveries due to preeclampsia or abnormal fetal Doppler were excluded. The standardized residuals for EFW and BW were calculated and compared.

Results: EFW and BW can be accurately described by quadratic equations (R²?=?0.944 and 0.807, respectively). The distribution of standardized residuals for BW using the EFW formula was negative from 28⁺⁰ to 35⁺⁶ weeks. The 50th and 5th centiles of BW were lower than those of EFW throughout prematurity, and they converged at approximately 38 gestational weeks. The 5th centile for BW was 30% lower than the 5th centile for EFW at 27 weeks, 27.5% lower at 30 weeks and 19.4% at 34 weeks.

Conclusions: Preterm infants have lower BW distribution compared to the expected EFW of ongoing pregnancies of the same gestational age, supporting the concept of hidden intrauterine morbidity for a proportion of these infants.     

Accuracy of ultrasonographic fetal weight estimation in twin pregnancies

OBJECTIVE: To compare the accuracy of fetal weight estimations between normal and growth-restricted twin and singleton pregnancies in a single tertiary center. METHODS: The computerized ultrasound database of a tertiary center was searched for all fetal weight estimations made in twin pregnancies from 2001 to 2006, which were performed up to 3 days before delivery. Accuracy was compared with a control group of singleton pregnancies at a 3:1 ratio. Estimated fetal weight was calculated by the Hadlock formula. Analyses were performed for the whole group and for pregnancies associated with fetal growth restriction and discordancy. RESULTS: The study groups included 278 twins and 834 singleton pregnancies. The twins group was characterized by a higher mean absolute percentage error compared with the singleton group (8.9% compared with 6.8%). Accuracy was lower for the second twins than for the first twins. When comparing the subgroup of fetal growth restriction, differences in sensitivity and specificity were small for singleton compared with overall twins (47.5% compared with 48.9% and 97.7% compared with 95.7%, respectively). Overall accuracy was better in the singleton group (95% compared with 88%), mainly due to relatively low accuracy in the second twin (86%). For detection of discordancy, estimated fetal weight had a sensitivity of 52%, specificity of 88%, and overall accuracy of 81%. CONCLUSION: The accuracy of the ultrasonographic estimated fetal weight seems to be lower for twin gestations than for singleton gestations, especially for second twins. These data should be considered by clinicians when making decisions based on ultrasonographic characteristics.     

Contribution of the umbilical cord and membranes to untrimmed placental weight

The extent of placental trimming before weighing varies within and between obstetric units. Quantification of the contribution of the umbilical cord and membranes to placental weight is required to enable measurements to be compared across populations. In a sample of 50 neonates born in Southampton, placentae of liveborn singletons were weighed three times; after removing any obvious blood clots, after cutting the umbilical cord, and after stripping both the foetal and maternal membranes.The correlation between untrimmed and trimmed placental weight was 0.98. Since the combined weight of the cord and membranes increased with increasing trimmed weight (correlation=0.54), the percentage rather than absolute difference between untrimmed and trimmed weight was calculated. The median difference between untrimmed and trimmed weight was 16 per cent. No association was found between the percentage difference and infant sex, duration of gestation, birthweight, maternal age, labour onset and duration, and presentation at delivery. However, the mode of delivery had a significant effect on this difference; medians for vaginal and Caesarean section deliveries were 19 per cent and 14 per cent respectively.     

Heart rate and blood pressure responses to umbilical cord compression in fetal lambs with special reference to the mechanism of variable deceleration

We examined heart rate and blood pressure responses to umbilical cord compression in fetal lambs. Fetal heart rate (FHR) responses resembling variable deceleration occurred only after umbilical blood flow was reduced by at least 50%. These changes during partial cord occlusion varied directly with the reduced umbilical blood flow and were abolished by atropine; no significant changes in arterial pressure were observed. Complete cord occlusion caused severe bradycardia, a progressive increase in arterial pressure, and delayed recovery of FHR. With partial cord occlusion, the bradycardia was of chemoreceptor origin and was vagally mediated; with complete occlusion the bradycardia may have resulted from both chemoreceptor and baroreceptor stimulation. During prolonged partial cord occlusion, FHR decreased initially, then recovered to above control value; this occurred in the face of a significant acidosis. Thus, FHR responses to cord compression are dependent on the actual percentage of reduction in umbilical blood flow and on its duration.     

Placental volume relative to fetal weight estimated by sonography in diabetic pregnancies

Objective: Our purpose was to analyze the fetal weight and placental volume (PV) ratio in diabetic pregnancies during mid-pregnancy.

Method: One hundred and forty nine diabetic pregnancies [75 gestational diabetes mellitus (GDM) and 74 diabetes mellitus type I (T1DM) with good glycemic control] and 232 healthy patients were analyzed by three-dimensional sonographic volumetry of the placenta, while fetal weight was estimated by two-dimensional technique.

Results: The gestational age-specific estimated fetal weight (EFW) [EFWGDM: 1840.8?±?932.82?g; EFWT1DM: 1475.6?±?914.7?g (mean?±?standard deviation) and placental ratio (PR)] was significantly higher (p?<?0.05) in pregnancies complicated by GDM and T1DM (PRGDM: 5.5?±?1.67?g/cm³, PRT1DM: 4.56?±?3.2?g/cm³) compared to control group (Q) (EFWQ: 532?±?186.49?g; PRQ: 2.2?±?0.8?g/cm³), whereas PV was significantly higher (p?<?0.05) only in GDM (PVGDM: 334.3?±?111.5?cm³) compared to control data (PVQ: 232?±?78.9?cm³). In contrast to GDM, T1DM with good glycemic control did not predispose to any changes in placental sonographic volumetric differences compared to control values.

Conclusions: Fetal weight related to the PV is already elevated in second trimester in pregnancies complicated by gestational diabetes mellitus and type I diabetes mellitus compared to normal pregnancies.     

A case of fetal vesicoallantoic cyst in the umbilical cord

A vesicoallantoic cyst in the umbilical cord was detected by fetal ultrasonography at 16 weeks of gestation. The blood flow through the umbilical vessels was evaluated with periodic color Doppler ultrasonographic examinations because compression by the cyst may cause reduction in blood flow and lead to fetal death. After disappearance of the cyst, the infant was delivered vaginally. Retrograde cystography revealed a narrow channel between the bladder and the navel, confirming patent urachus, which was resected without any complications.     

Pseudotumors of the umbilical cord and fetal membranes.

Antenatally diagnosed pseudotumors, i.e. non-neoplastic tumors, of the umbilical cord and fetal membranes may when scanned by ultrasound have an appearance leading to misdiagnosis. In the present cases, a hematoma in the fetal membranes was interpreted as a chorioangioma, and a cystic mass inside the umbilical cord caused by degeneration of Wharton's jelly was regarded as an omphalomesenteric or allantoic cyst. The two cases are presented. Color Doppler evaluation seems advisable.     

Amniotic fluid index and estimated fetal weight for prediction of fetal macrosomia: a prospective observational study

Objective: The purpose of this study was to assess the value of combining the estimated fetal weight (EFW) and amniotic fluid index (AFI) measured in term patients early in labor with intact membranes for prediction of macrosomia.

Methods: In a single center, prospective observational study, 600 patients in the first stage of labor before rupture of membranes in whom ultrasonography was performed to measure AFI and EFW, and these data were analyzed statistically to evaluate prediction of fetal macrosomia.

Results: Macrosomia occurred in 64 cases (10.6%). The AFI was significantly higher in the macrosomic group (p?=?0.001). It was noted that the area under receiver operating characteristic (ROC) curves for EFW was 0.93 and that of AFI was 0.67. Based on suggested combined EFW and AFI cutoffs of 4000?g and 164?mm, respectively, the positive predictive value (PPV) for combined parameters (92.3%) was higher than that of EFW (75%) and that of AFI (27%) and the likelihood ratio for combination (93.7%) was higher than that of EFW (24.7%) and that of AFI (21%).

Conclusion: Combined use of EFW and AFI improves prediction of macrosomia at birth rather than the EFW alone.     

3D-ultrasound detection of fetal grasping of the umbilical cord and fetal outcome

A case of persistent fetal palmar grasping of the umbilical cord in a 23-year-old primigravida is described. Palmar grasping was detected with three-dimensional ultrasound examination after cardiotocographically recorded fetal bradyarrhythmia. Because of acute fetal hypoxia, urgent Misgav-Ladach cesarean section was performed to deliver a hypotrophic female newborn, 2,120 g/43 cm, Apgar score 4/7, pH 7.29. No other pathology was found during the procedure. The postoperative course proceeded uneventfully and the early neonatal neurological status and neurosonographic findings were normal.     

Accuracy of sonographically estimated fetal weight with and without oligohydramnios. A case-control study

OBJECTIVE: To determine the accuracy of sonographically estimated fetal weight among women with and without oligohydramnios (amniotic fluid index [AFI] < or = 5.0 cm) and to ascertain the ability to detect fetal growth restriction (FGR) (estimated birth weight < 10th percentile for gestational age [GA]) among patients in two groups. STUDY DESIGN: Assuming that 50% of sonographic predictions are within 10% of the birth weight in the study group, 300 parturients are necessary to show a difference of 15% among controls (alpha = .05, beta = .02). The study group consisted of parturients with a reliable GA of > or = 24, no known anomalies and known AFI of < or = 5.0 cm. The control (1:1) was the next patient with the same GA but AFI between 5.1 and 23.9 cm. The paired t test was used, and the odds ratio (OR) and 95% confidence interval (CI) were calculated. P < .05 was considered significant. RESULTS: Among the study and control groups (N = 162 each), maternal demographics, mean estimate (P = .078) and actual birth weight (P = .091) were similar. Sonographic estimates within 10% of weight were not significantly different among those with (57%) and without oligohydramnios (59%; OR 0.92; 95% CI 0.59, 1.44). The frequency of FGR was higher among those with inadequate fluid (18%) than controls (9%; OR 2.13; 95% CI 1.10, 4.16). Sensitivity, positive predictive value and likelihood ratio were higher among those with oligohydramnios (76%, 78% and 16) than controls (53%, 42% and 7). CONCLUSION: The accuracy of sonographic estimates of fetal weight is not influenced by whether the parturient has oligohydramnios. Moreover, the accuracy of identifying FGR is not diminished among those with AFI < or = 5.0 versus > 5.0 cm.     

Renal response of fetal lamb to complete occlusion of umbilical cord.

The renal response of the fetal lamb to repeated complete occlusion of the umbilical cord was studied in nine chronically instrumented animals. Five episodes of occlusion of the umbilical cord, each lasting for two minutes, produced a twofold rise in fetal urine osmolality and sodium, chloride, and potassium concentrations. Output of urine and glomerular filtration rate remained essentially unchanged while free water clearance decreased from a control of +0.10 to -0.02 ml. per kilogram per minute at the end of the fifth episode. Electrolyte concentrations in urine remained elevated for at least two hours following the occlusions. In addition to changes in urine composition, there was a 50- to 200-fold increase in the fetal plasma concentration of vasopressin. These studies indicate that complete interruption of the umbilical circulation, even though of short duration, produces disturbances in fetal renal function that can lead to loss of electrolytes in the urine. They provide an explanation for the low sodium levels reported in asphyxiated newborn infants in renal failure.     

Electrocardiographic changes following umbilical cord occlusion in the midgestation fetal sheep

BACKGROUND: Clinical studies show that analysis of the fetal electrocardiographic (FECG) ST waveform at term gives important information on the myocardial response to intrapartum asphyxia. However, it is not known whether the preterm fetus responds in a similar fashion. The objective of the present study was to evaluate the FECGST response to umbilical cord occlusion in the preterm fetal sheep. METHODS: Fetal sheep at midgestation were subjected to 25 min umbilical cord occlusion (n = 7) and compared to controls (n = 5). Changes in the FECGST waveform were recorded together with arterial blood pressure, heart rate, and acid base status during the occlusion and for 3 days afterward. RESULTS: Umbilical cord occlusion resulted in immediate bradycardia (control: 187 +/- 7 bpm versus occlusion: 102 +/- 7 bpm), hypertension (control: 43.2 +/- 1.1 mmHg versus occlusion: 59.8 +/- 2.2 mmHg), and an initial increase in the T/QRS ratio (control: 0.10 +/- 0.02 versus occlusion: 0.60 +/- 0.10, P < 0.001), followed by hypotension (21.7 +/- 1.2 mmHg), normalization of the T/QRS ratio, and in some cases the development of negative T waves toward the end of the occlusion. CONCLUSIONS: These studies show that the midgestation fetal sheep has the capacity to react to umbilical cord occlusion with a significant increase in the amplitude of the ST waveform together with an augmentation of blood pressure, which then subsides as the occlusion continues. The appearance of negative ST segment appears to signify significant cardiac dysfunction. The characteristic progression of ST-waveform changes in response to umbilical cord occlusion in midgestation fetal sheep, suggests that monitoring the ST waveform may contribute clinically important information also in the preterm individual.