Doppler and birth weight Z score: predictors for adverse neonatal outcome in severe fetal compromise
- Fernanda C da Silva†1, 2Email author,
- Renato A Moreira de Sá†1, 2,
- Paulo RN de Carvalho†2 and
- Laudelino M Lopes†2
© da Silva et al; licensee BioMed Central Ltd. 2007
Received: 06 March 2007
Accepted: 20 March 2007
Published: 20 March 2007
An adequate placental perfusion is crucial for the normal growth and well being of the fetus and newborn. The blood flow through the placenta can be compromised in a variety of clinical situations, always causing important damage to the gestation. Our objective is to identify significant predictors for adverse neonatal outcome in severe fetal compromise.
Consecutive premature fetuses at between 25 and 32 weeks with severe placental insufficiency were examined prospectively. Inclusion criteria were: (i) singletons (ii) normal anatomy; (iii) abnormal umbilical artery Doppler pulsatility index (PI); (iv) abnormal cerebroplacental ratio; (v) middle cerebral artery (MCA) PI < - 2SD ("brain sparing"); (vi) last Doppler examination performed within 24 hours prior to delivery. All 46 patients that met criteria and started the study were followed to the end. We considered as independent potential predicting variables: absent or reversed end diastolic flow in umbilical artery, abnormal ductus venosus S/A ratio, absent or reversed flow during atrial contraction in the ductus venosus and birth weight Z score. Outcome parameters were: neonatal mortality and severe neonatal morbidity.
Backward stepwise logistic regression analysis was used to determine the optimal model for the prediction of neonatal mortality and severe neonatal morbidity. In this analysis birth weight Z score index showed the strongest association OR = 1,87 [1,17-2,99] with all neonatal outcome, all other independent variables were excluded for the optimal model. There was no mortality for the group with normal birth weight Z score.
Our study suggests that birth weight Z score is the strongest predictor of adverse neonatal outcome in severe placental insufficiencies. Such use of Z scores, allowing to get rid of gestational age or sex covariates could be extended to estimated fetal weight and might help in making important decisions in the management of compromised pregnancies.
An adequate placental perfusion is crucial for the normal growth and well being of the fetus and newborn. The blood flow through the placenta can be compromised in a variety of clinical situations, always causing important damage to the gestation.
Placental insufficiency promotes compensatory hemodynamic fetal changes including blood flow redistribution towards essential fetal organs, at the expense of others . The fetal compensatory response results in increased blood flow to the brain, also called the "brain sparing effect" . On the other hand, there is reduction in fetal growth, of liver size, and a reduction or absence of fat deposit. As the placental disease progresses, however, the fetus no longer can keep his vital organs functioning, ultimately leading to severe compromise with acid-base disturbance and death.
Doppler analysis, mainly the umbilical artery indices, signals the malfunctioning of the placenta. Doppler can monitor the fetal hemodynamic changes, as the more the fetus is compromised, the more the arterial and venous flow is deteriorated. Nevertheless, Doppler examination is not absolute and additional information is necessary to adequately assess fetal status .
The challenge in monitoring pregnancies complicated by placental insufficiency remains today, as no method of diagnosis or follow-up is complete. The dilemma involves essentially premature babies since the effects of prematurity need to be highly considered. Research is still needed to help finding the best time of delivery, when the effects of fetal hipoxia become worse than those of the low gestational age and weight.
Gestational age at delivery showed strong association with all postpartum complications . Using Z score indices, gestational age effect and gender effect can be removed. Our hypothesis is that Doppler and birth weight Z score index must be important to predict neonatal outcome. The aim of this investigation was to examine the relationship between, Doppler, birth weight Z score and adverse neonatal outcome in severe fetal compromise.
Between November 2003 and December 2006, all patients referred, between 25 to 32 weeks, with severe fetal compromise were examined prospectively. Inclusion criteria were: (i) singletons (ii) normal fetal anatomy; (iii) umbilical artery Doppler pulsatility index (PI) more than 2 standard deviations (SD) above the gestational mean values ; (iv) abnormal cerebroplacental ratio (middle cerebral artery pulsatility index divided by umbilical artery pulsatility index) ; (v) middle cerebral artery (MCA) PI more than 2SD below the gestational age mean ("brain sparing") ; (vi) last Doppler examination performed within 24 hours prior to delivery. Gestational age was determined by last menstrual period and/or sonographic examination prior to 20 weeks of gestation . All 46 consecutive patients that met inclusion criteria agreed participating in the study, by signing a written informed consent, and none were lost in follow up.
This protocol was approved by Hospital Ethics Comitee (protocol number 08/2005).
Z scores according to the reference charts for estimated fetal weight  were calculated in all cases using the following formulae:
Z score = (X GA - M GA )/SD GA
Where XGA is the measured birth weight at a known gestational age (GA), MGA is the mean value according to the reference used at this GA and SDGA is the standard deviation of the mean value at this GA according to the reference.
Outcome analysis was limited to the neonatal period. Outcome parameters were: neonatal mortality and severe neonatal morbidity. The clinical course at the neonatal period was reviewed for all surviving infants. The criteria for classification as severe neonatal outcome are the presence of one of following diagnoses: periventricular-intraventricular hemorrhage (PIH) grade 3 or 4, retinopathy of prematurity (ROP) stage 3 or 4, cystic periventricular leukomalatia (CPL) or broncopulmonary dysplasia (BPD) .
Stepwise logistic regression analysis was performed to determine the optimal model for the prediction of neonatal outcome. The Fisher's exact test was used to compare the frequency of outcomes between groups. The area under receiver-operator characteristic (ROC) curve was calculated for the significant independent variable, p < 0.05 was considered statistically significant.
All statistical analyses were performed using SPSS for Windows, version 10.0 (SPSS, Inc., Chicago, Illinois).
The study period was from November 2003 to December 2006. The mean gestational age at Doppler imaging was 28 weeks gestation, with the mean interval from Doppler imaging to delivery of 3 days.
All forty-six patients that initiated the study were included in the follow up. In 34 fetuses (74%) there was absent or reverse end-diastolic flow in umbilical artery. Nineteen fetuses (41%) had an abnormal ductus venosus S/A ratio. In 04 fetuses (9%) there was absent or reversal flow during atrial systole in ductus venosus. Twenty-two fetuses (48%) had birth weight Z score index below lower limit (-1.645).
Results of backward stepwise logistic regression analysis for neonatal outcome.
-Birth weight Z score
-Absent or reversal end diastolic flow in umbilical artery.
-Abnormal ductus venosus S/A ratio
-Absent or reversal flow during atrial systole in ductus venosus.
-Birth weight Z score
-Absent or reversal end diastolic flow in umbilical artery.
-Abnormal ductus venosus S/A ratio.
-Absent or reversal flow during atrial systole in ductus venosus
Z score birth weight index for the prediction of neonatal outcome.
Although there are many underlying etiologies, IUGR resulting from placental insufficiency is most relevant clinically because outcome could be altered by appropriate diagnosis and timely delivery. It is important to analyze which fetus is at risk and which is the parameter to be considered for timely delivery. Fetal growth restrictions are a physical sign rather than a single disease . Noninvasive antenatal surveillance tools, such as Doppler ultrasound are limited.
Multivessel Doppler surveillance is usually used in the assessment of the fetus at risk. The goal of fetal surveillance in high risk fetuses is to balance fetal and neonatal risk to optimize the timing of intervention. Deterioration of uteroplacental function is initially reflected by abnormal blood flow in the arterial Doppler and ongoing compromise is manifested by abnormal venous Doppler [3, 14]. There is a clear association between severe degrees of umbilical Doppler abnormalities, such as absent or reverse end-diastolic velocities and poor pregnancy outcome. Based on previous studies, we assumed that cerebroplacental ratio is potentially more advantageous in predicting outcome . The fetus with abnormal cerebroplacental ratio is usually the one that might benefit from timely appropriate management.
Multivessel Doppler assessment is not absolute and additional information is necessary to estimate the neonatal prognosis. The relationship between abnormal arterial and venous Doppler findings and neonatal outcomes is not well clarified [16, 17]. It is important to identify the fetus at risk for adverse neonatal outcome to intervene appropriately and to avoid over treatment and unnecessary fetal and maternal risk.
Our study has demonstrated that pathological Doppler findings in conjunction with fetal weight Z score index can identify the fetus at risk for neonatal mortality and morbidity. We speculate that Z score index can result in significant clinical improvement to predict the outcome of severe placental insufficiency.
- Bamberg C, Kalache KD: Prenatal diagnosis of fetal growth restriction. Semin Fetal Neonatal Med 2004, 9: 387-94. 10.1016/j.siny.2004.03.007View ArticlePubMedGoogle Scholar
- Bahado-Singh RO, Kovanci E, Jeffres A, Oz U, Deren O, Copel J: The Doppler cerebroplacental ratio and perinatal outcome in intrauterine growth restriction. Am J Obstet Gynecol 1999, 180: 750-6. 10.1016/S0002-9378(99)70283-8View ArticlePubMedGoogle Scholar
- Baschat AA, Gembruch U, Harman CR: The sequence of changes in Doppler and biophysical parameters as severe fetal growth restriction worsens. Ultrasound Obstet Gynecol 2001, 18: 571-7. 10.1046/j.0960-7692.2001.00591.xView ArticlePubMedGoogle Scholar
- Arduini D, Rizzo G: Normal values of pulsatility index from fetal vessels: a cross-sectional study on 1556 helthy fetuses. J Perinat Med 1990, 18: 165-72.View ArticlePubMedGoogle Scholar
- Wladimiroff JW, Tonge HM, Stewart PA: Doppler ultrasound assessment of cerebral blood flow in the human fetus. Br J Obstet Gynaecol 1986, 93: 471-5.View ArticlePubMedGoogle Scholar
- Nyberg DA, Abuhamad A, Ville Y: Ultrasound assessment of abnormal fetal growth. Semin Perinatol 2004, 28: 3-22. 10.1053/j.semperi.2003.10.010View ArticlePubMedGoogle Scholar
- Hecher K, Campbell S, Doyle P, Harrington K, Nicolaides K: Assessment of fetal compromise by Doppler ultrasound investigation of fetal circulation. Arterial, intracardiac, and venous blood flow velocity studies. Circulation 1995, 91: 129-38.View ArticlePubMedGoogle Scholar
- Wladimiroff JW, Van Der Wijngard JAGW, Degani S, Noordam MJ, Van Eyck J, Tonge HM: Cerebral and umbilical arterial blood flow velocity waveforms in normal and growth-retarded pregnancies. Obstet Gynecol 1987, 69: 705-9.PubMedGoogle Scholar
- Rizzo G, Cappohni A, Talone PE, Arduini D, Romanini C: Doppler indices from inferior vena cava and ductus venosus in predicting pH and oxygen tension in umbilical blood at cordocentesis in growth-retarded fetuses. Ultrasound Obstet and Gynecol 1996, 7: 401-10. 10.1046/j.1469-0705.1996.07060401.xView ArticleGoogle Scholar
- Schwärzler P, Bland JM, Holden D, Campbell S, Ville Y: Sex-specific antenatal reference growth charts for uncomplicated singleton pregnancies at 15–40 weeks of gestation. Ultrasound Obstet Gynecol 2004, 23: 23-29. 10.1002/uog.966View ArticlePubMedGoogle Scholar
- Moreira de Sá RA, Lopes LM, Dourado ALM, Costa Junior IB, Novaes BC: Antepartum Fetal Testing in Pré-eclampsia Model – Índices from Ductus Venosus – Cutt-Off Point. Hypertens Pregnancy 2004, (suppl 01):89.
- Vermont Oxford Network – Release 10.0. Manual of Operations for Infants Born in 2006 69-80.
- Brodsky D, Christou H: Current concepts in intrauterine growth restriction. J Intensive Care Med 2004, 19: 307-19. 10.1177/0885066604269663View ArticlePubMedGoogle Scholar
- Senat MV, Schwarzler P, Alcais A, Ville Y: Longitudinal changes in the ductus venosus, cerebral transverse sinus and cardiotocogram in fetal growth restriction. Ultrasound Obstet Gynecol 2000, 16: 19-24. 10.1046/j.1469-0705.2000.00159.xView ArticlePubMedGoogle Scholar
- Pardi G, Buscaglia M, Ferrazzi E, Bozzetti P, Marconi AM, Cetin I: Cord sampling for the evaluation of oxygenation and acid-base balance in growth-retarded human fetuses. Am J Obstet Gynecol 1987, 92: 31-8.Google Scholar
- Baschat AA, Gembruch U, Reiss I, Gortner L, Weiner CP, Harman CR: Relationship between arterial and venous Doppler and perinatal outcome in fetal growth restriction. Ultrasound Obstet Gynecol 2000, 16: 407-13. 10.1046/j.1469-0705.2000.00284.xView ArticlePubMedGoogle Scholar
- Baschat AA, Galan HL, Bhide A, Berg C, Kush ML, Oepkes D: Doppler and biophysical assessment in growth restricted fetuses: distribution of test results. Ultrasound Obstet Gynecol 2006, 27: 41-7. 10.1002/uog.2657View ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.