Prenatal findings in generalized amyoplasia

Amyoplasia is a rare, sporadic condition characterized by different degrees of maldevelopment of the skeletal muscles, which are replaced by fibrous and fatty tissue. In this report, we present a case of generalized amyoplasia presenting at 19 weeks' gestation. The most striking finding was the absence of fetal movements, resulting in severe multiple congenital contractures, hydrops, and polyhydramnios. At autopsy, histological examination of the skeletal muscle showed small groups of poorly developed fibres within areas of fat. This report suggests that generalized amyoplasia could be a common cause of severe forms of multiple congenital contractures, but is probably underdiagnosed at post-mortem because of inadequate examination of muscles. Definitive diagnosis is important in determining the risks of recurrence in these cases.

Prenatal detection of preaxial upper limb reduction in trisomy 18

BACKGROUND

Abnormalities of the upper and lower extremities, such as club feet, rocker-bottom feet, and abnormal hand posturing, are frequently detected prenatally in trisomy 18 fetuses. Aplasia of the radius, usually associated with the absence or hypoplasia of the first metacarpal and thumb, is the most prevalent reduction malformation in trisomy 18 infants. Because this anomaly is easily missed during prenatal ultrasonography, the role of prenatal detection of this particular preaxial upper limb reduction has not been emphasized.

CASES

Three cases of trisomy 18 in which preaxial upper limb reduction (radial aplasia) was identified prenatally by ultrasound are reported. Although in all cases there were additional ultrasonographic findings suggestive of trisomy 18, the prenatal detection of preaxial upper limb reduction facilitated the diagnosis.

CONCLUSION

Ultrasonographic examination of fetal forearms for the detection of preaxial upper limb reduction should be a routine part of the prenatal evaluation of fetuses in whom trisomy 18 is suspected.

Uptake of meta-analytical overviews of effective care in English obstetric units

OBJECTIVE

To establish the current availability of meta-analytical overviews of effective care in perinatal medicine, in the form of Effective Care in Pregnancy and Childbirth and the Oxford Database of Perinatal Trials, in English obstetric units and to find out how obstetricians without either one keep up to date.

DESIGN

Standardised telephone questionnaire.

SUBJECTS

The consultant obstetrician deemed to be the Royal College of Obstetricians and Gynaecologists' administrative contact in each of the 24 teaching hospitals, and in 74 of 173 (43%) district general hospitals in England.

MAIN OUTCOME MEASURES

Knowledge and use of Effective Care and the Oxford Database in the obstetric unit.

RESULTS

Thirty-seven percent of units did not have access to either Effective Care or the Oxford Database, with significant differences between district general hospitals and teaching hospitals in lack of availability (33/74 (45%) versus 3/24 (12%) respectively, P = 0.02). Effective Care was available in 51% of district general hospitals and 79% of teaching hospitals, compared with the availability of the Oxford Database which was only available in 16% and 62%, respectively. Reasons given for not obtaining either included non-awareness, expense, and perceived lack of need. The consultants with neither Effective Care nor the Oxford Database claimed to keep up to date by various methods, usually as information from colleagues.

CONCLUSIONS

These results reflect both inefficient dissemination of medical knowledge in obstetrics and the reluctance of obstetricians to consider adapting their practice as a result of evidence from meta-analyses of randomised controlled trials. Although Effective Care is more widely available than the Oxford Database, its datedness renders it inferior to the database as a means of facilitating effective care in obstetrics.

Angioarchitecture of monochorionic placentas in relation to the twin-twin transfusion syndrome

OBJECTIVE

Twin-twin transfusion syndrome in the midtrimester is associated with a perinatal mortality rate exceeding 80%. Although attributed to intertwin transfusion along vascular anastomoses, these occur in all monochorial placentas, not just the 10% with twin-twin transfusion syndrome. We compared fetoplacental angioarchitecture in monochorionic twin placentas with and without twin-twin transfusion syndrome.

STUDY DESIGN

The fetoplacental circulations of both twins in 20 monochorial placentas were perfused immediately after delivery under optimal physiologic conditions and anastomoses delineated by dye-contrast injection. Ten were from pregnancies with evidence of midtrimester twin-twin transfusion syndrome and 10 were from pregnancies without twin-twin transfusion syndrome.

RESULTS

Placentas from pregnancies with twin-twin transfusion syndrome had significantly fewer anastomoses than did those without twin-twin transfusion syndrome, both overall (median one versus six, respectively; p < 0.001) and for each of the different types (arterioarterial, venovenous, and arteriovenous, p < 0.001). Whereas multiple anastomoses were present in all controls, only one twin-twin transfusion syndrome placenta had more than a single communication. Anastomoses in the twin-twin transfusion syndrome group were more likely to be of the deep than the superficial type (80% vs 36% in controls, p < 0.01).

CONCLUSIONS

Placental vascular anastomoses in monochorial pregnancies complicated by twin-twin transfusion syndrome are both fewer in number and of a different type than those without twin-twin transfusion syndrome. These differences seem implicated in the underlying pathophysiologic features of twin-twin transfusion syndrome and are of relevance to the development of newer therapies such as placental laser surgery.

True knot of the umbilical cord: a difficult prenatal ultrasonographic diagnosis

We examined retrospectively the use of ultrasonography in 18 cases in which a true knot of the umbilical cord was found at delivery. All women had a normal second-trimester scan in which no cord abnormality was detected. Thirteen (72%) also had third-trimester color Doppler ultrasonography, at which time the cord anomaly was again missed. In one of these cases the diagnosis could have been made with color flow imaging, but the abnormal pattern was mistaken instead for multiple loops of cord. On the other hand, the diagnosis of true knot was considered prenatally in two cases, but not confirmed at delivery, when only a prominent false knot was found in one and a normal cord in the other. We conclude that true knots of the umbilical cord do not have a characteristic appearance in utero and therefore are easily missed at routine prenatal ultrasonography.

Fetal cholecystomegaly: a prenatal marker of aneuploidy

The fetal gall bladder can now be easily identified during the second and third trimesters using high-resolution ultrasonography. In this report we present eight fetuses with an enlarged gall bladder detected on prenatal ultrasonography at a mean gestational age of 24.6 weeks (range 19-31 weeks). Additional ultrasonographic findings were present in four cases: fetal anomalies and intrauterine growth retardation in three and polyhydramnios in one. Of those cases associated with fetal anomalies, one women underwent amniocentesis at 21 weeks revealing trisomy 18. The other two declined prenatal karyotyping; neonatal karyotyping revealed trisomy 13 in one and trisomy 18 in the other. Although an enlarged fetal gall bladder can be a normal variant in the second and third trimesters, the prenatal detection of cholecystomegaly should prompt a search for associated anomalies and other markers of aneuploidy. If found, prenatal karyotyping should be considered.

Single-cell analysis of the RhD blood type for use in preimplantation diagnosis in the prevention of severe hemolytic disease of the newborn

OBJECTIVE

Our purpose was to develop a molecular assay to determine the fetal RhD blood type on single diploid cells, including blastomeres.

STUDY DESIGN

Polymerase chain reaction amplification of a 99 bp deoxyribonucleic acid fragment of the RhD gene or a 113 bp fragment from the RhCE gene was performed from 20 venous blood samples and 20 amniotic fluid samples and from 60 single-cultured lymphoblasts and 12 media blanks mixed in a blinded fashion. This reaction was similarly tested after whole-genome amplification on 10 lymphoblasts and seven human blastomeres.

RESULTS

Deoxyribonucleic acid amplification was successful and correct from all genomic deoxyribonucleic acid samples. Ninety-seven percent of single cells amplified; correct diagnosis was made in 96%. Five blastomeres successfully amplified. No media blanks produced amplified, contaminating deoxyribonucleic acid.

CONCLUSIONS

The RhD blood type can be determined reliably from single cells and can be used for preimplantation genetic diagnosis for the prevention of rhesus hemolytic disease.

Exencephaly in autosomal dominant brachydactyly syndrome

Exencephaly was diagnosed at 17 weeks in a 27-year-old primigravida with abnormalities of the hands and a family history suggestive of autosomal dominant brachydactyly and clinodactyly. In this family there was also a history of 'anencephaly'. To our knowledge, this is the first report on the association of exencephaly and autosomal dominant brachydactyly. As the relationship between hand and cranial anomalies is well established, we suggest that this association in our case could be due to a defect in the same gene.

Are routine alpha-fetoprotein and acetylcholinesterase determinations still necessary at second-trimester amniocentesis? Impact of high-resolution ultrasonography

OBJECTIVE

To audit routine measurement of alpha-fetoprotein (AFP) and acetylcholinesterase in amniotic fluid (AF) samples obtained at second-trimester amniocentesis.

METHODS

We reviewed retrospectively 1737 consecutive AF specimens obtained for cytogenetic evaluation over a 4-year period and routinely assayed for AFP and acetylcholinesterase. In all instances, high-resolution ultrasonography was performed before amniocentesis. Details of pregnancy outcome of all cases with AF AFP levels greater than 2.0 multiples of the median and a positive or faint acetylcholinesterase band were obtained.

RESULTS

There were 31 abnormal results (1.8%, 1 of 56). Of these, 25 cases had elevated AF AFP and/or positive acetylcholinesterase. Ultrasonography correctly identified all 18 fetuses with anomalies associated with abnormal levels of these biochemical markers, including open neural tube defects and/or anterior abdominal wall defects (17 cases) and fetal hydrops (one). In the remaining seven, no fetal anomalies were detected, and all neonates were structurally normal after birth. In addition, six pregnancies with faint acetylcholinesterase and normal AF AFP showed no fetal abnormalities at ultrasonographic examination and post-delivery.

CONCLUSIONS

High-resolution ultrasonography was more accurate than AF biochemistry in the detection of congenital anomalies associated with elevated AFP levels and acetylcholinesterase in the AF. Routine measurement of these biochemical markers in AF samples obtained for cytogenetic analysis appears to have a very low yield and would therefore not be cost-effective in practices where high-resolution ultrasonography is performed before amniocentesis.

Antenatal lung maturation--should we all be using thyrotropin-releasing hormone?

Thyrotropin-releasing hormone (TRH) appears to be a promising antenatal therapy to help reduce neonatal lung disease. Clinical trials, however, show differing results. At present the optimum dosage, frequency and method of administration have not been established. TRH has been shown significantly to elevate blood pressure in patients with preeclampsia suggesting it should not be used in this group. Moreover concerns over its use in growth retarded fetuses and its long-term neonatal effects have not been addressed. Further trials are needed before routine clinical use can be recommended.

Third-trimester hyperechogenic bowel in Down syndrome

The association between second-trimester hyperechogenic bowel and Down syndrome has been well established in the literature. In this report we present a case of Down syndrome in which this finding was only detected during the third-trimester scan, after normal bowel echogenicity was documented in the second trimester. This report suggests that hyperechogenic bowel could be a late manifestation of Down syndrome.

Fetal intraluminal gastric masses after second trimester amniocentesis

Eight instances of homogeneous, well-defined echoes within the fetal stomach were identified on routine second trimester detailed scan over a 7 month period, a prevalence of 1 in 287 or 0.35%. This finding was significantly more frequent in women who had cytogenetic amniocentesis than in those who had not had the procedure (4 in 266 [1.5%] versus 4 in 2031 [0.2%], respectively; P < 0.01). Indirect signs of intra-amniotic bleeding, such as particles in the amniotic fluid, chorioamniotic separation, or hyperechogenic bowel, were present in four cases. The association between echogenic material within the fetal stomach and cytogenetic material within the fetal stomach and cytogenetic amniocentesis is discussed.

Discordant iliac and femoral artery flow velocity waveforms in fetuses with single umbilical artery

OBJECTIVE

The aim of this study was to investigate pelvic and femoral arterial flow velocity waveforms in fetuses with a single umbilical artery.

STUDY DESIGN

Seven fetuses with single umbilical artery and no other ultrasonographically detected anomalies were studied with color Doppler ultrasonography at a median gestational age of 24 weeks (range 18 to 34 weeks). Flow velocity waveforms from the relevant vessels were obtained as follows: (1) umbilical artery from a free loop of cord, (2) common iliac artery from both sides just below the aortic bifurcation, (3) internal iliac artery and intraabdominal portion of the umbilical artery from the vessel visualized alongside the fetal bladder, and (4) femoral artery on both sides from the upper third of the fetal thigh. The pulsatility index was measured, and comparisons were made with the paired t test. A p value < 0.05 was considered significant.

RESULTS

The pulsatility index in the umbilical artery was normal in all cases. There were highly significant differences between the common iliac arteries in each side (difference in pulsatility index 2.7, 95% confidence interval 2.0 to 3.5, p < 0.001). Significant differences between both femoral arteries were also noted (difference in pulsatility index 1.0, 95% confidence interval 0.3 to 1.7, p < 0.001). In both vessels the pulsatility index was always higher in the side that did not participate in the placental circuit.

CONCLUSION

This study demonstrates that fetuses with single umbilical artery have asymmetric arterial blood flow patterns in the pelvic and lower extremities.

Fetal plasma cortisol and beta-endorphin response to intrauterine needling

The purpose of this study was to investigate whether the fetus mounts a hormonal stress response to a potentially painful procedure, intrauterine needling. Cortisol and beta-endorphin concentrations in fetal plasma obtained during uncomplicated fetal blood sampling or intrauterine transfusions by needling the fetal intra-abdominal portion of the umbilical vein (intrahepatic vein) were compared to hormone concentrations in fetal plasma obtained by the conventional technique of needling the placental cord insertion, which is not innervated. Cortisol and beta-endorphin concentrations did not increase within 10 minutes of fetal abdominal needling (n = 15). However, more prolonged needling during transfusion at the intrahepatic vein was associated with an increase in fetal plasma cortisol (median increase 48 nmol/L; 95% Cl, 23-86) and beta-endorphin (207 pg/mL; 113-307) concentrations compared to transfusion at the placental cord insertion (p < 0.005 for both hormones). The magnitude of rise in hormone increased linearly with the duration of needling (cortisol, r = 0.80; beta-endorphin, r = 0.88, p < 0.05 for both). These data suggest that the fetus mounts a hormonal stress response to invasive procedures. They raise the possibility that the human fetus feels pain in utero, and may benefit from anaesthesia or analgesia for invasive procedures.

Clinical utility of fetal RhD typing in alloimmunized pregnancies by means of polymerase chain reaction on amniocytes or chorionic villi

OBJECTIVE

Our purpose was to describe the clinical utility of a deoxyribonucleic acid amplification method for determining fetal RhD status in alloimmunized pregnancies

STUDY DESIGN

Six RhD-negative women with alloimmunized pregnancies and heterozygous partners underwent amniocentesis (n = 5) or chorionic villus sampling (n = 1). Fetal RhD type was determined by polymerase chain reaction and results disclosed to the attending physicians.

RESULTS

Knowledge of the fetal RhD status avoided further invasive procedures in two pregnancies and facilitated the timing or performance of intrauterine transfusions in the remainder.

CONCLUSIONS

In alloimmunized pregnancies the ability to RhD-type the fetus in amniotic fluid avoids the risks of fetomaternal hemorrhage and increased sensitization associated with fetal blood sampling or chorionic biopsy. This allows more rational pregnancy management, avoiding invasive procedures in the presence of an RhD-negative fetus, or planning therapeutic interventions or offering termination of pregnancy in the presence of an RhD-positive fetus.

The influence of operator transducer pressure on ultrasonographic measurements of amniotic fluid volume

OBJECTIVE

Our purpose was to study the effect of operator transducer pressure on amniotic fluid index and single deepest pool measurements and their intraobserver and interobserver variability.

STUDY DESIGN

Forty subjects in the third trimester with intact membranes were studied by two observers at three predetermined operator pressures. Pressure was measured by interfacing a flexible water-filled reservoir connected to a manometer between the maternal abdomen and the ultrasonography transducer. The amniotic fluid index and single deepest pool were measured on screen by another operator, and data were analyzed by calculating components of variance.

RESULTS

Compared with medium pressure, low pressure resulted in a 13% increase in amniotic fluid index (p < 0.001), and high pressure resulted in a 21% fall in amniotic fluid index (p < 0.001). The single deepest pool was less sensitive to pressure, with a 11% increase at low pressure (p < 0.001) and a 16% fall at high pressure (p < 0.001). Intraobserver error was 17% for amniotic fluid index and 18% for single deepest pool when operator pressure was controlled at medium pressure; this increased to 28% and 24%, respectively, when pressure was not controlled (p < 0.01). Interobserver error was consistently very low.

CONCLUSION

Both techniques are highly sensitive to the pressure applied to the maternal abdomen during scanning. The reproducibility of amniotic fluid index and single deepest pool is comparable. The use of the same observer for serial measurements of amniotic fluid index would appear to be less important than careful attention to transducer pressure.

Potential for pre-implantation determination of human platelet antigen type using DNA amplification: a strategy for prevention of allo-immune thrombocytopenia

To demonstrate that fetal human platelet antigen (HPA1) type can be determined by amplification from picogram quantities of DNA, nested oligonucleotide DNA primers were designed to amplify a portion of the platelet glycoprotein GpIIIa gene which spans the polymorphic HPA site. Specific oligonucleotides were designed to hybridise either to the amplified HPA1a allele or to the HPA1b allele. DNA dilutions were used as a template and HPA1 type, determined by this method from as little as 2 pg of DNA in 6 cases, was compared to direct typing of blood from the same individuals. In each case nested polymerase chain reaction amplified the specific HPA locus from as little as 2 pg of DNA and determination of HPA1 type agreed with typing of blood.

Clinical and echographic features of in utero cardiac dysfunction in the recipient twin in twin-twin transfusion syndrome

OBJECTIVE

Fetal twin-twin transfusion syndrome (TTTS) presenting in the second trimester has been associated with almost no perinatal survival until recently, when serial drainage of amniotic fluid has improved the prognosis to 70%-80%. Most recipient twins now survive but develop cardiac dysfunction. The study was undertaken to evaluate the abnormal echocardiographic features and clinical complications of cardiac disease in the recipient twin of TTTS.

DESIGN

Antenatal and postnatal echocardiographic and clinical observational study.

SETTING

Antenatal studies in a tertiary referral centre. Postnatal management and follow up were performed by the same paediatric cardiologist, either at the obstetric hospital or at the regional referral centre.

PATIENTS

Twin pregnancies complicated by TTTS with severe polyhydramnios diagnosed earlier than 25 weeks that proceeded until viability (n = 5).

INTERVENTION

Serial fetal echocardiography with colour Doppler. Postnatal echocardiography in the first week and between two and seven months. Serial amnioreduction was performed in all pregnancies. Digoxin treatment, pericardiocentesis, paracentesis, or laser ablation of placental anastomoses was undertaken when there was hydrops.

RESULTS

Increased cardiothoracic ratio and tricuspid regurgitation were seen in all recipient twins. High pulmonary artery velocities developed in three. One recipient twin died a week after delivery of endocardial fibroelastosis and infundibular pulmonary stenosis. Two other had balloon dilatation for pulmonary stenosis, one shortly after birth and one at four months. A further twin has apical thickening of the right ventricle at six months. The remaining recipient twin had normal echocardiographic findings at follow up.

CONCLUSION

This report characterises for the first time a cardiac disease acquired in utero in the recipient twin in pregnancies complicated by TTTS. Clinical manifestations in utero range from mild to critical pulmonary stenosis or lethal cardiomyopathy. Although perinatal prognosis seems to be related to the severity of dysfunction when first diagnosed in utero, follow up in infancy is recommended in view of the possibility of progressive pulmonary stenosis.

Erythropoietic suppression in fetal anemia because of Kell alloimmunization

OBJECTIVE

Our purpose was to test the hypothesis that maternal anti-Kell alloimmunization produces fetal anemia by erythroid suppression.

STUDY DESIGN

Erythropoiesis in 11 anemic fetuses from maternal anti-Kell alloimmunization was compared with that in 11 fetuses where the mother was alloimmunized to RhD; each was matched for hematocrit, gestational age, hydrops, and perinatal outcome. Comparisons of the difference were performed by either paired t or Wilcoxon tests.

RESULTS

The anti-Kell group had reduced reticulocytosis (p = 0.007) and erythroblastosis (p = 0.045) and lower amniotic fluid bilirubin concentrations (p = 0.02) in comparison with the anti-D group. No correlation was found between hematocrit and reticulocytosis in the anti-Kell group, whereas the anti-D group had a significant linear relationship (r = 0.63, p < 0.05), indicating a progressive reticulocytosis in response to the degree of anemia.

CONCLUSION

These findings suggest that erythroid suppression, rather than hemolysis, is the predominant mechanism in producing fetal anemia related to maternal Kell alloimmunization. Fetal blood sampling is the investigation of choice in the evaluation of anemia related to maternal Kell alloimmunization, because reduced hemolysis means amniotic fluid bilirubin concentrations correlate poorly with anemia.

Fetal hyperechogenic bowel following intra-amniotic bleeding

OBJECTIVE

To test the hypothesis that increased echogenicity of the fetal bowel at second-trimester scans results from intra-amniotic bleeding.

METHODS

We studied 726 patients undergoing second-trimester amniocentesis for advanced maternal age. Three groups were identified according to the color of the amniotic fluid (AF) obtained: clear fluid, blood-stained fluid, and dark brown fluid. Two to 4 weeks after the amniocentesis, all patients had a targeted ultrasound examination for the detection of fetal structural anomalies and markers of chromosomal abnormalities, which included a survey of the fetal bowel. The incidence of hyperechogenic bowel in each group was compared by Fisher exact test. P < .05 was considered significant.

RESULTS

In 694 cases, the AF was clear (95%), in 20 blood-stained (3%), and in 12 dark brown (2%). Hyperechogenic bowel was detected in 14 fetuses with clear fluid (2%), in two with blood-stained fluid (10%), and in three with dark brown fluid (25%). Fetuses with proven intra-amniotic bleeding (ie, dark brown or blood-stained AF at amniocentesis) had a significantly higher incidence of hyperechogenic bowel compared to those with clear AF (five of 32 [15.6%] and 14 of 694 [2.0%], respectively; P < .001, 95% confidence interval for the difference in proportions 6.3-17.6%).

CONCLUSIONS

Our study demonstrates that intra-amniotic bleeding is associated with an increased incidence of fetal hyperechogenic bowel at second-trimester ultrasound scans. This sonographic phenomenon may be due to the presence of blood in the fetal bowel caused by fetal swallowing of bloody AF.

Direct fetal administration of immunoglobulins: another disappointing therapy in alloimmune thrombocytopenia

Current management strategies to prevent fetal intracranial haemorrhage in perinatal alloimmune thrombocytopenia (PAIT) include serial platelet transfusion and/or maternal high-dose intravenous immunoglobulin (IVIG) administration. The former involves multiple invasive procedures, while the latter is both expensive and of questionable efficacy. We report the use of direct fetal IVIG in 2 fetuses with PAIT, undergoing serial intrauterine platelet transfusions. Fetal IVIG had no effect on fetal platelet count. We conclude that direct fetal IVIG administration does not appear to have a role in the management of PAIT, and that current management strategies remain far from ideal.

Direct volume measurement at midtrimester amnioinfusion in relation to ultrasonographic indexes of amniotic fluid volume

OBJECTIVE

Our purpose was to investigate the relationship between amniotic fluid volume and semiquantitative ultrasonographic assessment of amniotic fluid in the midtrimester.

STUDY DESIGN

Sixteen pregnancies between 16 and 28 weeks with minimal amniotic fluid (severe oligohydramnios or anhydramnios) and intact membranes were studied at the time of clinically indicated amnioinfusion. The amniotic fluid index and deepest pool measurement were determined before and immediately after the procedure. Correlations were sought by means of standard regression techniques with amniotic fluid volume (i.e., volume infused) on the basis of the assumption that amniotic fluid volume before amnioinfusion was effectively nil.

RESULTS

There was a significant linear relationship between amniotic fluid index and volume infused (y = 7.336 + 0.015x; R2 = 0.30, p < 0.05). However, no correlation with the deepest pool measurement technique was found (R2 = 0.11, p > 0.05).

CONCLUSION

Amniotic fluid index is preferable to deepest pool measurement in assessing amniotic fluid volume in the second trimester of pregnancy. The low variance (30%) suggests that better predictors of amniotic fluid volume are still required.

The value of color Doppler ultrasound in the prenatal diagnosis of hypoplastic umbilical artery

The prenatal diagnosis of hypoplastic umbilical artery has recently been reported, based on the visualization of discordant size between both umbilical arteries in association with discordant umbilical artery flow velocity waveforms. In this report we present two cases of hypoplastic umbilical artery and describe the use of color flow imaging and Doppler ultrasound in the prenatal evaluation of this condition. The principal advantages of these techniques include the confirmation of blood flow within the hypoplastic artery, thus ruling out the possibility of an atrophic non-functional artery, and the demonstration of size discrepancy at the level of the intra-abdominal portion of the umbilical arteries, validating the intra-amniotic cord findings. Color Doppler ultrasound is an important tool for diagnosing and evaluating vascular anomalies affecting the umbilical cord.

Prenatal determination of human platelet antigen type using DNA amplification following amniocentesis

OBJECTIVES

To demonstrate that fetal human platelet antigen (HPA1) type can be determined, without the need for fetal blood sampling, by amplification of fetal DNA from amniotic fluid cells using polymerase chain reaction and allele specific oligonucleotide hybridisation.

DESIGN

Oligonucleotide DNA primers were designed to amplify a portion of the platelet glycoprotein GpIIIa gene which spans the site of the single base change which differentiates HPA1a from HPA1b. Specific oligonucleotides were designed to hybridise either to the amplified HPA1a allele or to the HPA1b allele. Amniotic cells were used as the DNA template both directly and following formal isolation of DNA. Fetal HPA1 type, determined by this method in fifteen pregnancies not at risk of perinatal alloimmune thrombocytopaenia, was compared to typing of fetal blood obtained following cordocentesis. The methodology was then used to HPA type the fetus in two pregnancies at risk of the disease.

SETTING

Department of Molecular Biology and Centre for Fetal Care, Queen Charlotte's Hospital.

SUBJECTS

Fifteen women undergoing amniocentesis and fetal blood sampling for other indications and two women at risk of perinatal allo-immune thrombocytopaenia whose partners were heterozygotes.

RESULTS

In the 15 control cases and the two clinical cases, determination of fetal HPA1 type from amniotic fluid cells agreed with typing of fetal blood. There was no difference in the efficiency of amplification from amniotic fluid cells directly or from isolated DNA.

CONCLUSIONS

Fetal HPA type may be reliably determined by amplification of DNA from amniotic fluid cells, eliminating the need for fetal blood sampling or immunoglobulin administration when the fetus is HPA1a negative.

Impaired fetal blood gas status in polyhydramnios and its relation to raised amniotic pressure

A substantial proportion of perinatal losses in polyhydramnios occur as unexplained normally formed stillbirths. In order to investigate the relationship between fetal condition and raised amniotic pressure (AP), fetal blood gas and acid-base status were determined together with AP in 22 pregnancies with polyhydramnios. At fetal blood sampling, 8 (36%) had a venous pH value and 16 (73%) a pO2 value below the reference range. Both fetal pH and pO2 were significantly negatively correlated with the degree of elevation in AP (y = 7.43 - 0.036x, r = 0.56, p = 0.006, where y = pH and x = AP z score, and y = -1.6 - 0.48x, r = 0.54, p = 0.01, where y = pO2 z score, respectively). Although some of these fetuses were hydropic, had congenital anomalies, or were from multiple pregnancies, univariate and multiple logistic regression analyses indicated that the above associations could not be accounted for by these potentially confounding variables. This work suggests that abnormal fetal blood gas status in human pregnancies with poly-hydramnios is associated with elevated AP.

Fetal blood sampling from intrahepatic vein versus cord insertion: effect on pH and blood gases

OBJECTIVE

To determine whether venous pH, base excess, and blood gas values collected by antenatal ultrasound-guided sampling from the fetal intrahepatic vein (intra-abdominal umbilical vein, portal sinus, or portal vein) differ from those obtained from the placental cord insertion.

METHODS

Retrospective analysis was done of 1053 clinically indicated fetal blood sampling procedures performed between 1988-1992. One hundred sixty-eight appropriate for gestational age (AGA) singleton fetuses were identified after exclusion of those with conditions believed likely to have impaired fetal blood gas status. Fetal venous pH, carbon dioxide pressure, oxygen pressure, and base excess from 52 samplings at the intrahepatic vein were compared cross-sectionally to those from 116 samplings at the placental cord insertion, using analysis of covariance to correct for gestational age.

RESULTS

There was no systematic difference in the blood gas or acid-base values between the two sites of fetal venous blood sampling.

CONCLUSIONS

Acid-base and blood gas status in AGA fetuses is not affected by the site of sampling. Values obtained at the intrahepatic vein may be interpreted using reference ranges derived from sampling at the placental cord insertion.

Amiodarone given by three routes to terminate fetal atrial flutter associated with severe hydrops

BACKGROUND

We describe the concurrent administration of amiodarone using three different routes in order to provide: 1) rapid and adequate fetal loading without giving unduly high doses to the mother, and 2) a maintenance dose to the fetus without risking repeated invasive procedures.

CASE

Rapid atrial flutter was seen on ultrasound in a fetus with severe hydrops at 27 weeks' gestation. Following failed transplacental therapy with sotalol and flecainide, amiodarone was administered to the fetus via the intravenous, intraperitoneal, and transplacental routes. Conversion to sinus rhythm and resolution of hydrops followed this treatment.

CONCLUSION

Combined triple-route administration of amiodarone to the fetus can be effective in treating supraventricular tachycardia and may have a role in the management of life-threatening fetal arrhythmias refractory to transplacental therapy.

Prenatal determination of fetal RhD type by DNA amplification

BACKGROUND

An RhD-negative woman whose partner is heterozygous may have preexisting anti-RhD antibodies that may or may not affect a subsequent fetus, depending on whether it is heterozygous. A safe method of determining fetal RhD type early in pregnancy would eliminate the risks to an RhD-negative fetus of fetal-blood sampling or serial amniocenteses.

METHODS

We determined the RhD type in 15 fetuses using the polymerase chain reaction in amniotic cells and serologic methods in fetal blood collected simultaneously. In another 15 fetuses, the RhD type determined from chorionic-villus samples was compared with that identified by typing of DNA from the fetus itself.

RESULTS

RhD typing of DNA from amniotic cells correctly indicated the serologic type in every fetus. Of 10 fetuses with RhD-negative mothers, 4 were identified as RhD-negative and 6 as RhD-positive. Of five fetuses with RhD-positive mothers, four were identified as RhD-positive and one as RhD-negative. There was also complete agreement between the results of RhD typing of DNA from chorionic-villus samples and the results of typing of DNA from fetal tissue. Eleven fetuses were RhD-positive, and 4 were RhD-negative. Four RhD-positive fetuses had RhD-negative mothers. Three RhD-negative fetuses had RhD-positive mothers. There was no contamination by maternal RhD-positive DNA of the samples from RhD-negative fetuses.

CONCLUSIONS

Determining fetal RhD type in amniotic cells without invading the fetomaternal circulation is a reliable method that will be valuable in the management of Rh alloimmunization.

Carbohydrate metabolism in fetuses with Rh alloimmunization

Glucose, insulin, glucagon and fructosamine were measured in the plasma of control (n = 34) and of Rh fetuses (n = 22) before the first and subsequent transfusion. Prior to treatment, Rh fetuses, compared to controls, had raised concentrations of glucose (p = 0.01), glucagon (p = 0.04) and fructosamine (p = 0.004). Fetal insulin levels were not significantly different. Before subsequent transfusion, despite correction of anemia, Rh fetuses were clearly hyperinsulinemic even after correction for gestation (p = 0.002) and had low glucagon concentrations (p = 0.01) when compared with values at the first transfusion. This metabolic milieu appears similar to that of fetuses of diabetic mothers which have increased plasma glucose and insulin during most of the last third of gestation.

Disappearing lung echogenicity in fetal bronchopulmonary malformations: a reassuring sign?

Congenital bronchopulmonary malformations detectable on prenatal ultrasound include cystic adenomatoid malformation (CAM), lobar sequestration, and upper airway atresia. We describe three fetuses with prenatally detected intrathoracic lesions in which the associated pulmonary hyperechogenicity disappeared before delivery. In the first case of pulmonary sequestration, the infant was asymptomatic after birth. However, in a case of CAM and another with laryngeal atresia, respiratory distress developed after delivery, despite recent scans showing apparently normal lung fields. This experience suggests that ultrasonic resolution of hyperechogenic lung lesions in utero does not necessarily indicate resolution of the underlying pathology.

Fetal ovarian cysts: diagnostic and therapeutic role for intrauterine aspiration

Antenatal diagnoses of fetal ovarian cysts have not usually been confirmed until postnatal surgery. We describe 2 cases of hemorrhage into fetal ovarian cysts in which cyst aspiration in utero allowed both confirmation of the diagnosis prenatally and obviated the need for neonatal surgery. In both cases, cytology of the cyst aspirate demonstrated luteinized granulosa cells and biochemistry showed estradiol levels of > 10,000 pmol/l, indicating ovarian etiology. Hemorrhage, which had been suspected on ultrasound, was confirmed by cytology, showing hemosiderin-laden macrophages. There was no evidence of recurrence in either case following aspiration. The described association of fetal hypothyroidism was excluded by testing thyroid function in cord blood and/or cyst aspirate. We suggest that intrauterine aspiration contributes to the management of fetal ovarian cysts by confirming their ovarian origin, demonstrating the presence or absence of hemorrhage and facilitating preservation of ovarian function both by reducing the risk of torsion and the need for neonatal surgery.

Transplacental transfer of cefuroxime in uncomplicated pregnancies and those complicated by hydrops or changes in amniotic fluid volume

The transplacental transfer of cefuroxime was determined at antenatal fetal blood sampling in a cross sectional study of 78 patients between 15-35 weeks' gestation, 8-138 minutes after a maternal intravenous dose of 750 mg. Mean serum cefuroxime concentration, measured by high performance liquid chromatography, was 7.4 (95% confidence interval (CI) 6.8 to 8.1) mg/l in control fetuses; concentrations in hydropic fetuses were similar (6.2 mg/l, CI 4.7 to 7.7) but in fetuses with oligohydramnios they were significantly lower, (4.9 mg/l, CI 3.6 to 6.2). Antibiotic concentration did not correlate with gestational age and remained unchanged by transfusion of packed red cells. We conclude that (i) fetal serum concentrations of cefuroxime obtained after a maternal dose of 750 mg are only adequate for prophylaxis against organisms with a minimum inhibitory concentration of < 4 mg/l and (ii) transplacental passage of cefuroxime is significantly reduced in the presence of oligohydramnios.

Cystic lesions of the fetal kidney: diagnosis and prediction of postnatal function by fetal urine biochemistry

Fetal urine was aspirated under ultrasound control from 21 large cystic renal masses in 18 pregnancies of 20 to 35 weeks gestation. None were associated with bladder or ureteric dilatation. At postnatal investigation, 12 kidneys were demonstrated to be hydronephrotic (5 with no or poor function) and 9 multicystic. Urinary concentrations of sodium (Na+), calcium (Ca++), and phosphate (PO4--) were significantly higher in the multicystic group than in the hydronephrotic, whereas urea and creatinine levels were lower. Determination of urinary PO4-- enabled differential diagnosis with no false-positive or false-negative cases. Among hydronephrotic kidneys, no biochemical parameter accurately predicted postnatal function, although creatinine was increased in all three nonfunctioning kidneys. In hydronephrotic kidneys, urinary Na+ concentration increased with advancing gestational age (r = .66; P < .02), suggesting that the duration of hydronephrosis has a negative effect on renal function.