Middle cerebral artery Doppler indices at different sites: prediction of umbilical cord gases in prolonged pregnancies

Middle cerebral artery Doppler pulsatility index as a predictor of intrapartum meconium release in prolonged pregnancies

OBJECTIVES

The aim of this study was to asses the correlation of middle cerebral artery pulsatility index (MCA-PI) and perinatal outcomes in prolonged pregnancies.

STUDY DESIGN

This was a prospective study of all consecutive pregnant women beyond 41 weeks' gestation attending for obstetric surveillance during a two years period. We evaluated the predictive value of MCA-PI lower than the 5th percentile (<p5) and the occurrence of: cesarean delivery for fetal distress, 5-min Apgar score <7, arterial cord pH < 7.15, presence of thick meconium at delivery, need for admission to the neonatal intensive care and/or neonatal death.

RESULTS

Three hundred and one pregnancies met the inclusion criteria and were managed expectantly. Of them, 31 (10.3%) fetuses had an MCA-PI < p5, which showed a significant relationship with the presence of thick meconium at birth (p < 0.001), but was not related to any of the other perinatal outcomes.

CONCLUSION

In prolonged pregnancies, the finding of MCA-PI < p5 is related to meconium emission at the time of delivery, but is not associated with an increased risk of adverse perinatal outcome.

Reference values for pulsatility index of fetal anterior and posterior cerebral arteries in prolonged pregnancy

OBJECTIVE

To establish consistent normal reference values for fetal anterior cerebral artery (ACA) and posterior cerebral artery (PCA) pulsatility index (PI) in prolonged pregnancy.

METHODS

This prospective cross-sectional observational study included singleton normal prolonged pregnancies into two study groups according to the gestational age: from 40 + 0 to 40 + 6 and from 41 + 0 to 41 + 6 weeks. The PI was assessed in both anatomical segments of ACA (ACA-S1 and ACA-S2) and of PCA (PCA-S1 and PCA-S2) with color Doppler imaging and pulsed Doppler examination, and reference centiles charts were generated. PI values from the two investigated segments of each vessel were also compared.

RESULTS

Data were obtained in 771 patients: n = 448 in the 40 + 0 and 40 + 6 weeks group, and n = 323 in the 41 + 0 and 41 + 6 weeks group. A moderate decrease in PI was observed as pregnancy progressed. No differences in PI values were found between the two anatomical segments of ACA and PCA.

CONCLUSION

This study provides Doppler reference values for the fetal ACA and PCA PI. It also shows that Doppler examination could be performed indifferently in one of the two anatomical segments of these arteries.

Reduced growth velocity from the mid-trimester is associated with placental insufficiency in fetuses born at a normal birthweight

BACKGROUND

Fetal growth restriction (FGR) due to placental insufficiency is a major risk factor for stillbirth. While small-for-gestational-age (SGA; weight < 10th centile) is a commonly used proxy for FGR, detection of FGR among appropriate-for-gestational-age (AGA; weight ≥ 10th centile) fetuses remains an unmet need in clinical care. We aimed to determine whether reduced antenatal growth velocity from the time of routine mid-trimester ultrasound is associated with antenatal, intrapartum and postnatal indicators of placental insufficiency among term AGA infants.

METHODS

Three hundred and five women had biometry measurements recorded from their routine mid-trimester (20-week) ultrasound, at 28 and 36 weeks' gestation, and delivered an AGA infant. Mid-trimester, 28- and 36-week estimated fetal weight (EFW) and abdominal circumference (AC) centiles were calculated. The EFW and AC growth velocities between 20 and 28 weeks, and 20-36 weeks, were examined as predictors of four clinical indicators of placental insufficiency: (i) low 36-week cerebroplacental ratio (CPR; CPR < 5th centile reflects cerebral redistribution-a fetal adaptation to hypoxia), (ii) neonatal acidosis (umbilical artery pH < 7.15) after the hypoxic challenge of labour, (iii) low neonatal body fat percentage (BF%) reflecting reduced nutritional reserve and (iv) placental weight < 10th centile.

RESULTS

Declining 20-36-week fetal growth velocity was associated with all indicators of placental insufficiency. Each one centile reduction in EFW between 20 and 36 weeks increased the odds of cerebral redistribution by 2.5% (odds ratio (OR) = 1.025, P = 0.001), the odds of neonatal acidosis by 2.7% (OR = 1.027, P = 0.002) and the odds of a < 10th centile placenta by 3.0% (OR = 1.030, P < 0.0001). Each one centile reduction in AC between 20 and 36 weeks increased the odds of neonatal acidosis by 3.1% (OR = 1.031, P = 0.0005), the odds of low neonatal BF% by 2.8% (OR = 1.028, P = 0.04) and the odds of placenta < 10th centile by 2.1% (OR = 1.021, P = 0.0004). Falls in EFW or AC of > 30 centiles between 20 and 36 weeks were associated with two-threefold increased relative risks of these indicators of placental insufficiency, while low 20-28-week growth velocities were not.

CONCLUSIONS

Reduced growth velocity between 20 and 36 weeks among AGA fetuses is associated with antenatal, intrapartum and postnatal indicators of placental insufficiency. These fetuses potentially represent an important, under-recognised cohort at increased risk of stillbirth. Encouragingly, this novel fetal assessment would require only one additional ultrasound to current routine care, and adds to the potential benefits of routine 36-week ultrasound.

Color doppler indices of proximal and distal parts of middle cerebral artery in fetuses with intrauterine growth restriction

INTRODUCTION

Intrauterine growth restriction (IUGR) is a major clinical issue for pregnant women. The purpose of this study was to evaluate color Doppler indices of the proximal and distal parts of the middle cerebral artery (MCA) of the fetus.

METHODS

In this cross-sectional study, 350 pregnant patients, with gestation age of 32-40 who were suspected to have intrauterine growth restriction, participated. The patients were referred for color Doppler sonography at the Imam Reza Hospital (Kermanshah, Iran) from May 2011 to September 2012. The following indices were measured for the proximal and distal part of the MCA: pulsatility index (PI), resistive index (RI), fetal heart rate (FHR), systolic to diastolic (S/D) ratio, and peak systolic velocity (PSV). The data were analyzed applying Tukey's-test, Paired-Samples t-test, and simple linear regression analysis using SPSS 19.

RESULTS

Average age of the mother, the frequency of pregnancy, and fetus gestational age were 27.79±0.17 years, 2.09±1.3, and 34.19±2.52 weeks, respectively. For gestation age of <36weeks, all Doppler indices of the distal part of the fetus MCA were significantly different from those of proximal part (p<0.05). Comparing indices of gestation age <36 weeks with those of >36 weeks, significant difference was found between the Doppler indices of the proximal parts as well as for the distal parts (p<0.05).

CONCLUSION

Measurement of fetus MCA indices may depend to the sampling location; however, this needs further investigation in order to find a clear probe location.

Review: Systematic review of the utility of the fetal cerebroplacental ratio measured at term for the prediction of adverse perinatal outcome

AIM

This systematic review evaluates the utility of the fetal cerebroplacental ratio (CPR) when assessed at term (from 37 + 0 weeks gestation) as a predictor of adverse obstetric and perinatal outcomes.

DATA SOURCES AND SEARCH STRATEGY

An electronic search of Pubmed and Embase using variations of 'cerebroplacental ratio' and 'cerebroumbilical ratio' was conducted by two independent reviewers. Full text studies written in English that reported on low CPR and its correlation with relevant obstetric and perinatal outcomes were included.

RESULTS

Twenty one studies satisfied inclusion with 13 prospective and eight retrospective analyses. Fetal CPR was predictive of caesarean section for intrapartum fetal compromise, small for gestational age and fetal growth restriction and neonatal intensive care unit admission. Low CPR was also significantly associated with abnormal fetal heart rate pattern, meconium stained liquor, low Apgar score, acidosis at birth and composite adverse perinatal outcome scores. The CPR when taken at term had comparable if not better predictive value than that when taken at preterm. Most studies included small for gestational age fetuses and postdate pregnancies. Subtle variation existed in the threshold for low CPR.

CONCLUSION

The CPR at term has a strong association with adverse obstetric and perinatal outcomes. This review suggests the predictive utility of CPR at term is promising however there is insufficient evidence to demonstrate its value as a stand-alone test. Inclusion of CPR as a component of clinical care may help better identify fetuses at risk of adverse outcome, and this should be tested with randomised control trials.

Role of cerebroplacental ratio for fetal assessment in prolonged pregnancy

OBJECTIVE

The aim of this study was to assess the role of the cerebroplacental ratio (CPR), i.e. the ratio between the middle cerebral artery and umbilical artery pulsatility indices, in detecting fetal compromise in prolonged pregnancy.

METHODS

Women attending a dedicated postdates clinic at 41 weeks' gestation were recruited for the study and CPR was calculated at 41+3 weeks. Induction of labor was offered at 42 weeks to those women still undelivered. Unfavorable outcome was defined as cord arterial pH < 7.15 with a base deficit of > 11 mM/L or operative delivery for abnormal intrapartum fetal electrocardiogram ST-segment analysis. The 5(th) centiles of the CPR, obtained from published reference ranges (0.90) and from our population (0.98), were used as lower cut-off values.

RESULTS

Three hundred and twenty women who reached a gestational age of over 41 weeks were eligible for inclusion in the study. The median gestational age at delivery was 294 (range, 289-300) days. Unfavorable outcome was observed in 58/320 pregnancies. There was no significant difference in the proportion of unfavorable outcomes between the two groups defined using either CPR cut-off value (both P > 0.05).

CONCLUSION

CPR is not predictive of unfavorable outcome in women with pregnancies lasting more than 41 weeks.

[Management of post-term pregnancies: the role for AFI, biophysical score and doppler]

OBJECTIVE

To evaluate the role of ultrasound and doppler assessment in the management of prolonged pregnancies and to state its modalities.

METHOD

Medline, PubMed, embase and the Cochrane library were searched using terms prolonged pregnancy, post date pregnancy amniotic fluid, ultrasound assessment, doppler, biophysical profile.

RESULTS

Single deepest vertical pool measurement is the method of choice of the assessment of amniotic fluid. Indeed, when this method was used, significantly fewer case of oligohydramnios were diagnosed and fewer women had inductions of labor. However, this method is not superior to the amniotic fluid index in the prevention of poor perinatal outcomes. There is a significant difference in the incidence of fetal distress, meconium stained fluid and caesarean section for fetal distress when the amniotic fluid is reduced as compared with normal amniotic fluid. However, sensibility and predictive positive value of oligohydramnios to predict poor perinatal outcomes is moderate. Similary, in most studies, diagnosis of an abnormal uterine, umbilical, aortic or cerebral blood flow doppler was associated with a weak prediction of a poor perinatal outcome. Therefore, we do not recommend its use in management of prolonged pregnancy. There were significantly more diagnosis of oligoamnios and more abnormal antenatal monitoring results in the modified biophysical profile group as compared with the group managed with only single deepest pool but no differences in cord blood gases, neonatal outcome, or in outcomes related to labour and delivery were noted between the two groups. Therefore, biophysical profile including AFI offers no advantage in detecting adverse outcomes and may cause more interventions.

CONCLUSION

Close monitoring of fetal condition including assessment of amniotic fluid by single deepest pool twice a week from 41 weeks of gestation is recommended in the management of prolonged pregnancy. Induction of labor could be considered when oligohydramnios is diagnosed by single deepest pool less than 2 cm.

Postdates and antenatal testing

The standard definition of a prolonged pregnancy is 42 completed weeks of gestation. The incidence of prolonged pregnancy varies depending on the criteria used to define gestational age at birth. It is estimated that 4 to 19% of pregnancies reach or exceed 42 weeks gestation. Several studies that have used very large computerized databases of well-dated pregnancies provided insights into the incidence and nature of adverse perinatal outcome such as an increased fetal and neonatal mortality as well as increased fetal and maternal morbidity in prolonged pregnancy. Fetal surveillance may be used in an attempt to observe the prolonged pregnancy while awaiting the onset of spontaneous labor. This article reviews the different methodologies and protocols for fetal surveillance in prolonged pregnancies. On the one hand, false-positive tests commonly lead to unnecessary interventions that are potentially hazardous to the gravida. On the other hand, to date, no program of fetal testing has been shown to completely eliminate the risk of stillbirth.