Placental pulsatility index: a new, more sensitive parameter for predicting adverse outcome in pregnancies suspected of fetal growth restriction.

INTRODUCTION: The pulsatility indices of the umbilical and uterine arteries are used as the surrogate measures of utero-placental perfusion. Combining the two might simplify the evaluation of total placental vascular impedance, possibly improve prediction of adverse outcomes, and help identify pregnancies with suspected fetal growth restriction that need more intense surveillance. MATERIAL AND METHODS: Umbilical and uterine blood flow velocities were recorded using pulsed-wave Doppler in a longitudinal study of 53 low-risk pregnancies (248 observations) during 20-40 weeks of gestation. Pulsatility indices was calculated for each of these vessels. A new placental pulsatility index was constructed as: (umbilical artery pulsatility index + mean of the left and right uterine artery pulsatility indices)/2, and mean +2 SD defined as abnormal. Gestational age-specific reference percentiles were calculated for the second half of pregnancy and related to values obtained from 340 pregnancies with suspected intra-uterine growth restriction to test its ability to predict adverse pregnancy outcome. RESULTS: The placental pulsatility index was closely associated with gestational age and decreased with advancing gestation in normal pregnancy. The placental pulsatility index had a higher sensitivity and comparable specificity in predicting adverse outcome in pregnancies suspected of intra-uterine fetal growth restriction when compared with conventional umbilical and uterine artery pulsatility indices. CONCLUSIONS: The new placental pulsatility index, reflecting placental vascular impedance on both the fetal and maternal side of placenta, improves prediction of adverse outcome in pregnancies suspected of intra-uterine fetal growth restriction.

Alterations in ductus venosus velocity indices in relation to umbilical venous pulsations and perinatal outcome.

INTRODUCTION: Abnormal blood velocity in the ductus venosus is more frequently detected than pulsations in the umbilical vein, but both are considered to be indicators of fetal compromise. The aim of this study was to investigate blood flow patterns in the ductus venosus and the association between individual blood velocity ratios and pulsations in the umbilical vein and perinatal outcome. MATERIAL AND METHODS: Retrospective cohort study on Doppler ultrasound examination of ductus venosus and umbilical venous blood velocity in 358 high-risk pregnancies. Ductus venosus blood velocity pattern was analyzed for pulsatility index and the following velocity ratios: S/ES, S/a and ES/a (where S is systole, ES is end-systole, and a is atrial contraction). Ductus venosus ratio z-scores were calculated and related to pulsations in the umbilical vein and adverse perinatal outcome. RESULTS: Systolic ratios in the ductus venosus were less frequently abnormal than ratios taking into account diastolic velocities, particularly at full-term. High S/ES, ES/a ratios and pulsatility index (z-score >2), were all related to presence of pulsations in the umbilical vein. Umbilical venous pulsations were the best indicator of adverse perinatal outcome. CONCLUSIONS: Changes in ductus venosus blood flow during systole occur more rarely than diastolic changes, and alterations in end-diastolic blood velocity in the ductus venosus might give false-positive indications of worsening fetal condition. Umbilical venous pulsations seem to better predict adverse outcome of pregnancy than do indices in the ductus venosus.

Investigations on atrial function in fetuses with signs of impaired placental function.

OBJECTIVE: Cardiac dysfunction has been shown in cases of placental insufficiency, but few reports exist on fetal atrial function. The aim of this study was to generate reference values for atrial strain and compare them to results in fetuses with signs of increased placental resistance and abnormal venous circulation. METHODS: Using a 2D speckle-tracking technique, velocity and strain of the fetal atrial walls were investigated in 250 healthy fetuses and in 40 fetuses with abnormal umbilical Doppler. Influences of gestational age, heart rate, and frame rate on the measurements were investigated and reference curves constructed. RESULTS: Strain and velocity were greater for the right atrial walls compared with the left, and velocity and strain rate increased with gestational age. Increased pulsatility of the ductus venosus and umbilical vein was not associated with altered right atrial function. CONCLUSIONS: 2D speckle-tracking analysis of fetal atrial wall movement seems to be feasible. Atrial function was preserved in fetuses with placental dysfunction, even in cases of increased venous pulsatility.

Uterine artery Doppler in high-risk pregnancies at 23-24 gestational weeks is of value in predicting adverse outcome of pregnancy and selecting cases for more intense surveillance.

OBJECTIVE: To assess the role of the placental arterial Doppler examination at 23-24 gestational weeks for predicting adverse perinatal outcome in high-risk pregnancies. DESIGN: Retrospective register study. SETTING: Skåne University Hospital in Malmö. POPULATION: Six hundred and forty-five women with high-risk pregnancies, without fetal malformations or chromosomal abnormalities. METHODS: Placental (uterine and umbilical artery) Doppler ultrasound examination at 23-24 gestational weeks. MAIN OUTCOME MEASURES: Adverse perinatal outcomes including preeclampsia, small-for-gestational age newborns (smaller than 3rd percentile or smaller than the 10th percentile), preterm delivery (<34 weeks or <37 weeks of gestation at delivery), cesarean section, admission to the neonatal intensive care unit and intra-uterine fetal death. RESULTS: Abnormal uterine artery Doppler values were detected in 45% of this high-risk group but abnormal umbilical artery Doppler indices were only seen in 3.7%. Adverse perinatal outcome increased significantly with increasing placental vascular impedance (p < 0.0001). There were seven cases of intrauterine fetal death and in five the uterine artery Doppler values at 23-24 weeks were abnormal. A strong correlation between abnormal uterine artery Doppler and preeclampsia was present, but not with other forms of hypertensive disorder. CONCLUSION: Placental Doppler screening at 23-24 weeks can be used in detecting pregnancies at risk of adverse outcome and in selecting cases for more intense surveillance. A surveillance plan is proposed based on Doppler screening at 23-24 weeks of gestation.

Fetal pulmonary and cerebral artery Doppler velocumetry in normal and high risk pregnancy.

UNLABELLED: Studies on fetal lung/brain circulation by means of power Doppler technique have suggested a marked reduction in lung perfusion in high-risk pregnancies as a sign of circulation redistribution. The ratio between lung/brain perfusion might therefore give a new method to predict fetal circulation centralization. OBJECTIVE: The aim of the present study was to obtain fetal lung and cerebral artery ratio in normal and high-risk pregnancies. STUDY DESIGN: Doppler samples from proximal right pulmonary artery blood velocities and middle cerebral artery (MCA) were recorded cross-sectionally in 228 normal singleton pregnancies at gestational age 22 to 40 weeks. MCA/right pulmonary artery pulsatility index (PI) ratio was calculated. Doppler samples from proximal right pulmonary artery and MCA were also recorded in 89 high-risk singleton pregnancies and the results related to perinatal outcome. RESULTS: In the normal controls, right pulmonary artery PI remained stable until 30 weeks of gestation with slight increase thereafter until term. The MCA to right pulmonary artery PI ratio increased between 22 and 28 weeks of gestation with the rapid fall towards term. In the high-risk pregnancies group, right pulmonary artery PI showed no significant correlation to perinatal outcome, but signs of brain-sparing in the MCA were correlated to all adverse outcome parameters. CONCLUSION: Velocimetry of the middle cerebral artery is better than velocimetry of right pulmonary artery in predicting adverse outcome of pregnancy The brain/lung PI ratio does not improve the prediction of adverse outcome of pregnancy.

Ultrasound measurements of umbilical cord transverse area in normal pregnancies and pregnancies complicated by diabetes mellitus.

OBJECTIVE: A voluminous umbilical cord has been described in diabetic pregnancies. The aim of this studywas to see if measurements of cord diameters might be of value in the evaluation of diabetic pregnancies and especially those suspected of a large for gestational age (LGA) fetus. METHODS: In an observational, prospective study umbilical cord areas and vessel diameters were measured between gestational age of 22 and 40 weeks in transverse ultrasound images of the central part of the cord in 141 normal and 135 diabetic pregnancies of which 30 were suspected of being LGA. Wharton's jelly area was calculated by subtracting the vessel area from the total transverse cord area. Normal reference curves were constructed for gestational age. RESULTS: Umbilical cord and Wharton's jelly areas increased with gestation. The vessel area leveled out at 32-33 weeks of gestation and the umbilical vein area decreased after 36 weeks of gestation. The umbilical cord parameters in diabetic pregnancies did not differ from controls. Cord areas were enlarged in 1/3 of the LGA fetuses. CONCLUSION: Umbilical cord area measurements are of limited value for the evaluation of diabetic pregnancies suspected having a LGA-fetus.

Ductus venosus opens in high-risk pregnancies without signs of increased central venous pressure.

OBJECTIVES: It has been belived that changes in diastolic blood velocities in the fetal ductus venosus were due to increased central venous pressure secondary to increased fetal heart strain during hypoxia or heart failure. There have been recent reports of changes in ductus venosus blood velocity without signs of increased fetal heart strain. The aim of this evaluation was to compare blood velocity in the right hepatic vein as a marker of increased central venous pressure in relationship to changes in ductus venosus blood velocity. MATERIAL AND METHODS: Fifty pregnancies suspected of fetal growth resitriction were evaluated by Doppler ultrasound. Blood velocity was recorded in the right hepatic vein, ducus venosus and in the umbilical vein. Placental blood flow was also recorded in the uterine and umbilical arteries as well as the fetal middle cerebral artery. RESULTS: Increased umbilical artery pulsatility index was recorded in 19 fetuses and 20 has signes of brain sparing according to recordings in the middle cerebral artery. Abnormal blood velocity in the ductus venosus was recorded in 5 fetuses, none of these fetuses had an abnormal pulsatility in the right hepatic vein. CONCLUSIONS: Opening of the ductus venosus is not only related to fetal cardiac strain. This might indicate that the ductus venosus does not primarily open due to increased central venous pressure in moderate fetal hypoxia. Increased fetal cardiac strain might be a late event in the process of chronic fetal hypoxia.

Characteristics and outcome of brachial plexus birth palsy in neonates.

AIM: To relate pregnancy characteristics to extent and reversibility of brachial plexus birth palsy (BPBP) in neonates. METHODS: Retrospective case-control study: newborns with a registered diagnosis of BPBP (n = 168) 1990-2005 were compared to data from a randomly selected control group (n = 1000). Characteristics were related to the level of injury, reversibility and outcome. RESULTS: Among 51,841 newborns, 168 cases with BPBP were found (incidence 3.2/1000 newborns/year). Extent and reversibility of lesion did not differ with respect to characteristics of mothers, foetuses or deliveries. Children with C5-C6 and C5-C6-C7 injuries had complete recovery in 86% and 38%, respectively. Global injuries (C5-Th1) always had permanent disability. Accelerators (foetal weight gain >35 g/day after 32 weeks of gestation) and foetuses with estimated weight deviation ≥ +22% at 32 weeks were at seven- and ninefold increased risk of BPBP. Parous women were at doubled risk as compared to nulliparous women. CONCLUSION: Maternal and foetal characteristics influence risk of BPBP, but not the extent of injury or reversibility of injury. Because of the high risk of permanent disability and modest risk of low Apgar or pH among newborns with BPBP, the recommendation of prompt delivery may need to be re-evaluated.

Biochemical tissue-specific injury markers of the heart and brain in postpartum cord blood.

OBJECTIVE: We sought to establish references ranges and to test the hypothesis that biochemical tissue-specific markers for the heart in umbilical cord blood of newborns with cardiac defects and intrauterine growth restriction (IUGR) are abnormal. STUDY DESIGN: A prospective study was conducted. Serum samples of the umbilical vein (n = 280) and artery (n = 156) from 599 healthy newborns at 37(+0)-42(+0) weeks of gestation were collected. Total creatine kinase (CK), CK-MB heart type (CK-MB), cardiac troponin T (cTnT), myoglobin, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and S100 were measured. Reference ranges for each marker were constructed. Concentrations of tissue-specific markers from umbilical cord blood of neonates with cardiac defects (n = 10) and IUGR (n = 41) were plotted against the established reference ranges. RESULTS: Reference ranges for each studied marker were established for both umbilical artery and vein. In fetuses with cardiac defects, both NT-proBNP (4/6 [66%] in the artery, 7/10 [70%] in the vein) and cTnT (2/10 [20%] in the vein) were increased. In fetuses with IUGR in the vein, NT-proBNP (10/41 [24%]) and cTnT (5/41 [12%]) were increased, whereas S100 (9/41 [21%]) was decreased. CONCLUSION: In a subset of neonates with cardiac defects or growth restriction, irrespective of the pH at birth, tissue-specific injury markers for the heart in umbilical cord blood are abnormal.

Abnormal uterine artery Doppler in pregnancies suspected of a SGA fetus is related to increased risk of recurrence during next pregnancy.

OBJECTIVE: To investigate if placental Doppler velocimetry can predict the recurrence of a small-for-gestational age (SGA) fetus in subsequent pregnancies. DESIGN: Retrospective study. SETTING: City cohort over 15 years attending a university hospital. METHODS: A total of 196 pregnancies suspected of a SGA fetus (<3rd percentile) evaluated by uterine and umbilical artery Doppler velocimetry. Blood velocity waveform was analyzed for pulsatility index (PI) as well as the uterine artery waveform for notching in early diastole. MAIN OUTCOME MEASURE: The occurrence of a SGA newborn during the succeeding pregnancy by Doppler results from the previous pregnancy. RESULTS: In the group of 196 pregnancies suspected for SGA, 27 (13.8%) delivered a SGA newborn in the following pregnancy. Thirty-seven (18.9%) of the 196 had an abnormally high PI in the uterine arteries in their first pregnancy, 12 (32.4%) of these delivered a SGA child in the next pregnancy (relative risk 3.44, p<0.001). The corresponding figure for those with normal uterine artery PI was 15 (9.4%). Abnormal umbilical artery Doppler was a worse predictor of recurrence of SGA (p=0.051). Uterine artery notching was not related to a SGA newborn during next pregnancy. CONCLUSION: The results suggest that abnormal uterine artery Doppler is related to increased risk of recurrence of SGA during the next pregnancy. This knowledge might provide the clinician with an opportunity to initiate preventive treatment and increase surveillance to women at risk during succeeding pregnancy.

TNF-alpha gene polymorphism and fetal Doppler velocimetry in intrauterine growth restriction.

OBJECTIVES: The intrauterine growth restriction (IUGR) frequently is a cause of fetal morbidity and mortality, and influences perinatal outcome. Several genes have been identified to explain aetiology of IUGR, beside others the gene coding for tumour necrosis factor alpha (TNF-alpha). DESIGN: To investigate frequency of AlwI polymorphism of TNF-alpha gene and its correlation with TNF-alpha level in maternal serum, Doppler velocimetry and perinatal outcome in pregnancies suspected for IUGR. SETTING: 42 pregnancies with IUGR and 50 matched healthy pregnant women were included in the study. Maternal venous blood samples were investigated in relationship to blood flow Doppler velocimetry in umbilical (UA) and middle cerebral (MCA) arteries. AlwI polymorphism was analysed using PCR/RFLP assays. TNF-alpha level was evaluated by immunoelectophoretic method. RESULTS: A higher frequency of mutated -238A alleles (13.1% vs. 7.0%) and genotypes containing at least one mutated -238A allele (23.8% vs. 14.0%) were found in the IUGR group. The tendency to the higher TNF-alpha level in IUGR subgroups with the presence of at least one mutated A allele (258.9+/-231.3 vs. 174.1+/-145.6 pg/ml) was detected. No statistical differences were detected for PI values in UA and MCA arteries considering particular genotypes (GG vs. GA + AA) separately in IUGR group. CONCLUSION: Increased UA vascular impedance and signs of brain sparing in MCA are related to IUGR and increased TNF-alpha level in maternal serum. AlwI polymorphism might play a role in IUGR aetiology and influence TNF-alpha expression in maternal serum, but was not related to Doppler velocimetry or with perinatal outcome.

Fetal biometry between 20-42 weeks of gestation for Polish population.

OBJECTIVE: Ultrasound estimating of fetal weight is one of the most frequent examinations during pregnancy. Hitherto, foreign fetometry curves have mostly been used in Poland as there are no national available reference charts that are based on ultrasound fetal biometry. The aim of the present study was to construct new charts based on ultrasound fetometry reference for Polish population. STUDY DESIGN: A group of 959 healthy volunteers with uncomplicated singleton pregnancy joined in a cross-sectional study. The study was designed prospectively to evaluate normal reference charts for fetal ultrasound measurements and estimated fetal weight. Four biometric parameters were studied: biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL). Estimated fetal weight (EFW) was calculated using Hadlock et al. formula from 1985. RESULTS: In the course of normal pregnancy an acceleration of growth rate was seen, but with a slight decline at the end of pregnancy. Reference curves for mean, 90th and 95th percentile were constructed for BPD, HC, AC and FL. Estimated fetal weight curves were outlined for both boys and girls. CONCLUSION: Reference charts for Polish population are similar to foreign curves. Less variation was seen in comparison with national charts based on postnatal weight. Ultrasound method seems to be better than birthweight curves especially in preterm pregnancies. This will improve the diagnosis of a small for gestational age newborn.

Abnormal uterine Doppler is related to vasculopathy in pregestational diabetes mellitus.

BACKGROUND: The aim of the study was to evaluate the relation between maternal placental Doppler velocimetry, levels of the maternal glucose, and clinical signs of vasculopathy in pregnancy complicated by pregestational diabetes mellitus. METHODS AND RESULTS: A retrospective study of 155 pregestational diabetic women between the 22nd and 40th weeks of pregnancy, categorized in White classification as B, 49; C, 40; D, 22; R, 20; F, 5; and RIF, 19. Cases in classes R, F, and R/F were defined as having vasculopathy. Doppler velocimetry of umbilical and uterine arteries was evaluated for vascular impedance, both in terms of pulsatility index (PI) for both arteries and a notch in early diastole in the uterine arteries. The last examination before delivery was used for analysis. Increased umbilical artery PI was seen in 19 and a uterine artery abnormality in 45 cases. There was a correlation between levels of HbA(1c) and increased vascular impedance in the uterine and umbilical arteries. Signs of increased uterine artery vascular impedances were significantly related to pregestational vasculopathy. In cases of small-for-gestational-age newborn infants, PI was significantly increased in uterine and umbilical arteries. Furthermore, PI in macrosomic fetuses was significantly lower than in normal infants. Abnormal uterine artery Doppler was also strongly related to adverse outcome. CONCLUSIONS: Abnormal uterine artery Doppler is related to pregestational vasculopathy and adverse outcome of pregnancy. The results suggest that the uterine arteries are affected in women with clinical signs of pregestational vasculopathy. This may influence placental perfusion and fetal well-being.

Flow index evaluation of 3-D volume flow images: an in vivo and in vitro study.

Three-dimensional (3-D) ultrasound imaging has improved evaluation of organ circulation and might contribute new information on maternal and fetal blood supply. Flow index (FI) of 3-D color images has been proposed as a measure of perfusion. The aim of this study was to evaluate whether the 3-D FI is a parameter of volume flow and flow velocity in a human vessel and in a flow phantom. A 1-cm-long strip of the uterine artery was recorded in 3-D power Doppler (3D-PD) mode in a cross-sectional study of 170 normal singleton pregnancies between 26 and 42 weeks' gestation. A fixed ultrasound system installation was used during the examination. The VOCAL software integrated in the ultrasound unit calculated vessel volume and FI. Reproducibility of the measurements was tested. The method was also tested on a commercially available flow phantom. Reproducibility measurements gave satisfactory results, both in terms of inter- and intraobserver variation. Unexpectedly, in normal pregnancy, the uterine artery FI decreased slightly with gestation. Uterine artery vessel volume increased, however, with gestational age. A poor correlation was found between the FI and both flow velocity and volume flow in the flow phantom. In conclusion, 3D-PD imaging can give impressive anatomical pictures of organ vascular tree. However, the new FI is poorly related to flow velocity or volume of flow.

Acute centralization of blood flow in compromised human fetuses evoked by uterine contractions.

BACKGROUND: During fetal hypoxia blood is redistributed to the brain ('brain-sparing'). Sequential changes of the cerebral and placental circulation in parallel in comparisons between basal conditions and acute hypoxic stress have not yet been thoroughly studied in human fetuses. AIM: To explore acute fetal middle cerebral artery (MCA) circulatory changes relative to umbilical artery (UA) blood flow in a clinical experimental model with hypoxic stress provoked by uterine contractions during an oxytocin challenge test (OCT). STUDY DESIGN: Prospective comparative between imminently compromised (OCT positive) and un-compromised (OCT negative) fetuses. SUBJECTS AND METHODS: 82 term pregnancies suspected of intrauterine growth restriction were exposed to simultaneous electronic fetal heart rate monitoring and Doppler recordings of pulsatility index (PI) in the UA and MCA during basal conditions and during uterine contractions and relaxations at an OCT. OUTCOME MEASURES: Sequential changes of UA and MCA PI, OCT positive vs. negative cases. Nonparametric statistics with a P < 0.05 considered significant. RESULTS: The UA PI was significantly higher in OCT positive cases (N = 10) compared with OCT negative cases (N = 72) during uterine contractions and relaxations, but not during basal measurements. During contractions and relaxations the MCA PI decreased significantly in both groups (brain-sparing), but significantly more in OCT positive cases. CONCLUSIONS: During acute hypoxic stress, changes towards a centralization of blood flow to the brain develop in imminently compromised (OCT positive) fetuses at an expense of the umbilicoplacental blood flow, and the brain-sparing flow is more pronounced than in un-compromised (OCT negative) fetuses.

Increased pulsatility in the fetal ductus venosus is not related to altered cardiac strain in high-risk pregnancies.

OBJECTIVE: Blood flow velocity patterns in fetal veins are considered to reflect cardiac function, but have not been convincingly documented. The aim of this study was to generate reference values for fetal cardiac strain and compare it with results in fetuses with signs of increased venous pulsatility. METHODS: Cardiac four-chamber loops were prospectively stored and analyzed for strain and strain rate in a cohort of 250 healthy fetuses. The results were compared with recordings in 38 fetuses with increased vascular impedance in the umbilical artery, including several with abnormal blood flow velocities in the ductus venosus (DVs) and umbilical vein. RESULTS: In the control group, strain rate was slightly higher in the right ventricle, but strain and velocities were similar. There was a significant effect of frame rate on the values of strain and strain rate, but not on velocity. No differences in cardiac strain or strain rate were observed between the control group and the compromised fetuses. There was no correlation between changes in venous blood flow and cardiac strain. CONCLUSIONS: Increased venous pulsatility was not related to fetal cardiac strain. This might indicate that the DVs does not primarily open due to increased central venous pressure and that cardiac strain is affected late in the process of moderate fetal hypoxia.

Computer analysis of three-dimensional power angiography images of foetal cerebral, lung and placental circulation in normal and high-risk pregnancy.

Three-dimensional (3-D) ultrasound (US) has greatly improved evaluation of organ circulation. The aim of this study was to explore the possible use of this new technique in normal and high-risk pregnancies. Fetal brain, lung and placenta 3-D power Doppler signal intensity were recorded in 115 normal singleton pregnancies (24 to 42 weeks gestation) and in 67 high-risk pregnancies. Mean image pixel signal intensity was calculated for each organ and a brain-lung ratio. In normal pregnancy, placental and lung signal intensity increased until 33, with a rapid decrease after 38, weeks of gestation. Fetal cerebral signal intensity increased with gestational age. Placental and fetal lung signal intensity was significantly lower in high-risk pregnancies than in the control group, with increased fetal brain and brain-lung ratios. The present results suggest a reduction of placental perfusion after 38 weeks of gestation in normal pregnancy, with redistribution of fetal circulation. Lung signal intensity increased abruptly at 32 weeks of gestation, which might reflect lung maturity. The new method showed signs of centralization of fetal circulation at the end of gestation. The results might suggest a possible clinical use for fetal surveillance in high-risk pregnancies.

No association between female circumcision and prolonged labour: a case control study of immigrant women giving birth in Sweden.

OBJECTIVE: Several authors' associate female genital circumcision with obstructed and prolonged labour, but the World Health Organization recently stated that no scientific evidence confirms such a relationship. The object of this study was to compare the duration of the second stage of labour between circumcised and non-circumcised women in a high-income community in Europe. METHODS: Sixty-eight circumcised nulliparous women originally from the Horn of Africa were compared to a group of 2486 non-circumcised nulliparous who gave birth at a university hospital setting in Sweden, 1990-1996. Defibulation was routinely performed during labour. FINDINGS: Circumcised women were found to have had second stage labour, which was significantly statistically shorter (35/53 min, respectively, p < or = 0.001) and a lower risk of prolonged labour than the non-circumcised group. CONCLUSIONS: Prolonged labour does not seem to be associated to female genital circumcision in affluent societies with high standards of obstetric care.

Incomplete protection by prophylactic surfactant against the adverse effects of large lung inflations at birth in immature lambs.

OBJECTIVE: To investigate whether preceding surfactant instillation prevents the harmful effect of large lung inflations at birth in immature lambs, and, if not, to find out for how long the immature lung remains sensitive to large inflations. DESIGN: In an exploratory study, 12 preterm lambs given surfactant at birth were randomized to receive five large lung inflations at four different times: at birth just before or immediately after surfactant treatment; at 10 min; or at 60 min of age. In a confirmatory study, 10 pairs of preterm lamb twins were all given surfactant before the first breath. One lamb in each pair was randomised to receive large lung inflations immediately after surfactant while the other twin underwent similar inflations at 10-15 min of age. SETTING: Animal laboratory. EXPERIMENTAL ANIMALS: Anaesthetized lambs delivered by cesarean section at a gestational age of 127 days. INTERVENTIONS: Surfactant supplementation at birth. Five sustained lung inflations of 16 ml/kg at different times in relation to surfactant instillation. Pressure-limited mechanical ventilation for 4 h. MEASUREMENTS AND RESULTS: The response to surfactant was assessed by ventilator settings, lung mechanics and lung histology. Preceding surfactant supplementation did not prevent the adverse effect of large lung inflations at birth on ventilatory efficiency and lung mechanics, but seemed to protect against severe lung injury. No adverse effect was seen from large lung inflations given at 10 min of age or later. CONCLUSION: Prophylactic surfactant supplementation does not fully protect against the harmful effect of large lung inflations during a short sensitive period immediately after birth.

Acute increase of umbilical artery vascular flow resistance in compromised fetuses provoked by uterine contractions.

BACKGROUND: An impaired placental circulation is involved in the mechanism of late fetal heart rate (FHR) decelerations. OBJECTIVES: To explore umbilical artery (UA) Doppler velocimetry changes in response to uterine contractions during the oxytocin challenge test (OCT) and assess the potentially clinical value of 'OCT Doppler velocimetry'. METHODS: 111 women with pregnancy complications were subjected to an OCT with simultaneous recordings of FHR and UA pulsatility index (PI). Positive OCT cases (late FHR decelerations) were compared with negative OCT cases (normal FHR patterns). Only negative OCT cases were allowed a trial of vaginal delivery. RESULTS: The UA PI was higher in OCT positive (N=21) than in negative cases (N=90) during uterine contractions and relaxations (P<0.05), but not during basal measurements. A positive OCT, but not negative, was associated with an increase of PI during contractions and relaxations compared with basal measurements (P<0.05). Fetal growth restriction (N=58), operative delivery for fetal distress (ODFD) in labor (N=10), and birth asphyxia (N=8) were not associated with PI changes significantly different from cases without these complications. CONCLUSIONS: During uterine contractions and relaxations, but not during basal measurements, a significantly higher UA PI evolved in OCT positive cases compared with OCT negative cases. This indicates a pathophysiological mechanism disclosed only during uterine activity. Although these changes would not have been revealed by traditional Doppler velocimetry, the data suggest a limited predictive value of 'OCT Doppler velocimetry' on the short-term neonatal outcome.