Abstract Background: A comparison of fetal ultrasonographic biometric parameters of the head head circumference - HC, biparietal diameter - BPD in breech presented fetuses. Publication types Research Support, Non-U. This ratio, when calculated from ultrasound examination in the third trimester, was also found to correlate well with the "breech head" shape.
Ultrasound identifi cation of these babies should prevent the misdiagnosis of fetal growth retardation based on serial BPD measurements alone.
The term "breech head" in reference to the cranial deformity was fi rst suggested by Haberker et al. The distinctive distortion of the cranium is presumably secondary to the forces applied to the growing cranium by the uterine fundus as the fetus is constrained in the breech position in late gestation, often with the head retrofl exed.
The term size, primiparity and oligohydramnios were recognized as additional factors predisposing to in utero constraint. In babies with "breech head" screened ultrasonographically by Kasby et al.
Once the constraint is relieved postnatally, the head shape has the potential for complete resolution. In itself, the deformation does not indicate an underlying calvarial or CNS structural malformation 1. It is likely that the altered head shape is a refl ection of intrauterine environmental factors and it suggests that the cranial abnormality under consideration is a postural deformation associated with the in utero breech position.
It is not known how early the head deformation can occur, but we have ultrasound evidence of marked dolichocephaly in the breech fetus as early as 31 weeks.
The evidence presented as well as our results show that in a considerable proportion of breech babies the BPD is smaller than expected from the commonly accepted norms without necessarily refl ecting growth retardation. It further acknowledges that gestational age prediction from the third trimester BPD is unreliable. This ratio is a measure of dolichocephaly and a value above 1. Third trimester ultrasound measurements of head circumference HC , femur length FL and abdominal circumference AC should be used in preference to the biparietal diameter BPD for the assessment of fetal growth.
HC and FL parameters correlate with gestational age. In cases of ultrasonographic biometric discrepancy between BPD and FL, the fetal position should be taken into account. Their evaluation system was simple, a score of 2 was assigned for each normal variable and 0 when the biophysical parameter was absent or abnormal. Recently, however, Manning and associates showed that the addition of the NST did not improve discriminative accuracy, when all the other four variables were normal.
The outcome used for measuring true or false normal test results was fetal death within 1 week of a normal biophysical profile. Their observed false-negative rate was 0. Overall, the results of the biophysical profile were normal, equivocal, or abnormal in The accuracy of the biophysical profile may be enhanced if guidelines to define prerequisites for the test are established. For example, to properly evaluate FBM a function governed by circadian rhythm and maternal glucose level , during the day.
Additionally, prior to testing it should be determined that the mother is not on medication known to inhibit the fetal CNS. The umbilical arteries UA and therefore Doppler interrogation of these vessels allows for the assessment of placental circulation.
In the normal placenta, the resistance to passive flow decreases with increasing gestational age. However, in the growth restricted fetus, often the resistance to flow increases leading to an overall decease in flow. It should be noted that it is the pathological conditions leading to IUGR and not fetal growth restriction itself that lead to abnormal umbilical artery Doppler values. A number of authors have evaluated and tested the efficacy of UA Dopplers in the monitoring of the growth restricted fetus.
In addition, there is continued debate regarding the implications of abnormal UA Doppler results. Unfortunately, the Doppler studies in isolation do not predict the timing of perinatal insults, and they are not able to predict which neonates will be compromised. Therefore, this type of monitoring should be used as an adjunct to other perinatal testing. It may be used to help guide the frequency of NST or biophysical profile testing in the at risk pregnancy.
Progressive decline in the flow, absent and finally reversed flow in the UA Doppler studies should prompt intensive fetal surveillance and may guide the decision to deliver when gestational age and other fetal surveillance are taken into account.
In most centers management protocols list use of the NST as the initial evaluation of the fetus with altered growth. In the event the test is nonreactive, a biophysical score is then obtained. UA Dopplers are used to determine the frequency of fetal testing, as abnormal Dopplers will prompt more frequent NSTs. Most obstetricians agree that in the face of IUGR and abnormal biophysical and bioelectric tests, intervention, regardless of pulmonary maturity, is necessary to prevent fetal death or asphyxia possibly leading to long-term CNS deficits.
By comparison the question of when to deliver an IUGR fetus, who has attained pulmonary maturity but in whom biophysical and bioelectric tests remain normal, has not been scientifically answered yet. Some physicians feel that, under these circumstances, delivery should be effected by 36—38 weeks' gestation, in the hope of preventing long-term CNS abnormalities.
Optimal diabetic antenatal care entails the early detection and appropriate management of fetal growth acceleration. The large-for-gestational age LGA neonate is at greater risk for perinatal mortality and morbidity when compared with the normal sized infant. In another study of infants weighing more than g, neonatal morbidity, neonatal mortality, and maternal morbidity were For clinical purposes, macrosomia is generally defined as a fetal weight in excess of g.
To effect improvement in perinatal care, the evolution as well as the extent or severity of macrosomia should be determined and quantified earlier in pregnancy and prior to term or attainment of maximal size and weight.
Toward this end, we concur with others who believe that fetal weight above the 90th centile for gestational age is a more meaningful clinical definition of macrosomia than is absolute birth weight. Our experience parallels that of Hadlock and associates who contend that LGA fetuses are a nonhomogeneous population with two main forms of macrosomia.
On the other hand, asymmetric macrosomia occurs in diabetic patients falling into White's A—C classification. In these asymmetric LGA fetuses the head and femur measurements vary in size and length but fall below the 90th centile rank.
Fetal abdominal circumference and thigh diameter, however, both reflect soft tissue mass and may be significantly larger than normal. Fetal macrosomia is difficult to predict in the antenatal period. In the other ten fetuses AC values exceeded the upper limits of normal 2 SD above the mean for nondiabetic pregnancies between 28 and 32 weeks' gestation; delivered at term, the reliability of the macrosomia index for detection of evolving macrosomia prior to term has not been determined.
Platt and associates reported that a transverse fetal thigh diameter greater than 5. Femur length is part of the standard biometric assessment of gesational age and fetal weight. Of clinical importance, vaginal delivery was attempted in of the diabetic gravidas.
The probability of cesarean delivery for disproportion in fetuses predicted to be macrosomic was Although several formulas are now available for sonographic estimation of fetal weight, to date, only two studies have evaluated the accuracy of fetal weight estimation for the detection of macrosomia. Because of this variation, a fetus weighing g may be estimated to weigh as little as g or as much as g. Clearly, such a wide range of estimates would result in a significant number of false-negative and false-positive results.
Korndorffer and associates, in a preliminary study, compared three methods for predicting macrosomia and were able to correctly diagnose only five of ten LGA fetuses by the best method. The standard deviation of differences was These authors caution that the large standard deviations of mean differences behoves the obstetrician to use clinical judgment and centile ranks of fetal sonar parameters in addition to weight estimates when planning delivery of fetuses suspected of being macrosomic.
Available methods for fetal antenatal assessment in diabetic pregnancies include biochemical urinary estriols , bioelectric antepartum fetal heart rate testing , and biophysical ultrasound modalities. Biochemical tests, specifically serial urinary estriol determinations, have served as the standard of fetal well-being against which the value of fetal heart rate testing has been compared. Recent reports, however, have seriously questioned the value of estriol determinations as the standard.
Further, the cost of serial estriols is high and there is a delay in obtaining laboratory results. Golde and associates used bioelectric and biophysical testing to manage insulin-dependent diabetic pregnant women.
Antepartum fetal heart rate testing AFHRT is, at present, the predominant approach used to assess fetal status in the insulin-dependent diabetic mother. As a result of the low false-negative rate, the contraction stress test CST has had the greatest clinical usefulness in diabetic gestations. The nonstress test NST , although widely used, has not been tested in large numbers of diabetic pregnancies. Whittle and associates and Dooley and associates have demonstrated that NSTs are superior to estriol determinations.
Dynamic ultrasound imaging provides another screening modality by allowing in utero observation of fetal activity. Although several aspects of fetal behavior have been studied, at present, fetal breathing movements FBM and body movements FM appear to be the most promising.
Natale and associates hypothesize that local excesses of carbon dioxide produced by increased glucose oxidation might stimulate fetal medullary chemosensitive areas and produce increased FBM. Improved neonatal care has sharply reduced the incidence of neonatal deaths in IDMs. As a result attention is presently being focused on antepartum and intrapartum methods that allow for the early detection and treatment of fetal disease.
In a prospective, blinded, clinical study they found that perinatal mortality consistently rose when the last test score prior to delivery fell. Whereas Of the 93 perinatal deaths, Of prognostic significance, completely normal test scores were associated with a perinatal mortality rate of 0. Clearly, large numbers of diabetic pregnancies must be serially assessed by biophysical profile testing before its accuracy can be precisely determined.
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J Pediatr , Methods: All ultrasound biometric measurements were performed according to the methodology published with the reference charts. Risk pregnancies, multiple pregnancies and breech presentations were excluded.
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