In utero therapy for lower urinary tract obstruction

Lower urinary tract obstruction has a significant impact on neonatal and child health. Pulmonary hyperplasia and renal impairment could be direct or indirect consequences of this condition leading to significant morbidity and mortality. Evaluation of fetuses with suspected lower urinary tract obstruction is performed not only to confirm the diagnosis but also to assess renal prognosis. Ultrasound examination and urinary analysis aid in the evaluation of these fetuses. The decision to perform fetal intervention in these cases is a difficult one. Vesico-amniotic fetal shunting, open fetal surgery and more recently endoscopic fetal surgery for this condition are available as possible modalities of fetal intervention. Case selection for fetal intervention is extremely important in order to both avoid unnecessary intervention in those unlikely to survive, and also to avoid procedure related complications in fetuses likely to do well without intervention. Vesico-amniotic shunting has the advantage of bypassing the obstruction, however it is often associated with complications. Open fetal surgery is not usually recommended because of the complications and high fetal loss rate. Endoscopic surgery to visualise and treat the cause of lower urinary tract obstruction has been tried. Fetal endoscopic surgery is in its infancy and endoscopic procedures are limited to a few groups. This current review addresses evaluation, case selection and therapeutic options for lower urinary tract obstruction in utero. It also discusses the limited data against which the efficacy of the various options can be assessed. The current state of fetal intervention is detailed in the present review.

Identification of mesenchymal stem/progenitor cells in human first-trimester fetal blood, liver, and bone marrow

Human mesenchymal stem/progenitor cells (MSCs) have been identified in adult bone marrow, but little is known about their presence during fetal life. MSCs were isolated and characterized in first-trimester fetal blood, liver, and bone marrow. When 10(6) fetal blood nucleated cells (median gestational age, 10(+2) weeks [10 weeks, 2 days]) were cultured in 10% fetal bovine serum, the mean number (+/- SEM) of adherent fibroblastlike colonies was 8.2 +/- 0.6/10(6) nucleated cells (69.6 +/- 10/microL fetal blood). Frequency declined with advancing gestation. Fetal blood MSCs could be expanded for at least 20 passages with a mean cumulative population doubling of 50.3 +/- 4.5. In their undifferentiated state, fetal blood MSCs were CD29(+), CD44(+), SH2(+), SH3(+), and SH4(+); produced prolyl-4-hydroxylase, alpha-smooth muscle actin, fibronectin, laminin, and vimentin; and were CD45(-), CD34(-), CD14(-), CD68(-), vWF(-), and HLA-DR(-). Fetal blood MSCs cultured in adipogenic, osteogenic, or chondrogenic media differentiated, respectively, into adipocytes, osteocytes, and chondrocytes. Fetal blood MSCs supported the proliferation and differentiation of cord blood CD34(+) cells in long-term culture. MSCs were also detected in first-trimester fetal liver (11.3 +/- 2.0/10(6) nucleated cells) and bone marrow (12.6 +/- 3.6/10(6) nucleated cells). Their morphology, growth kinetics, and immunophenotype were comparable to those of fetal blood-derived MSCs and similarly differentiated along adipogenic, osteogenic, and chondrogenic lineages, even after sorting and expansion of a single mesenchymal cell. MSCs similar to those derived from adult bone marrow, fetal liver, and fetal bone marrow circulate in first-trimester human blood and may provide novel targets for in utero cellular and gene therapy.

Interstitial laser: a new surgical technique for twin reversed arterial perfusion sequence in early pregnancy

Current treatments for twin reversed arterial perfusion sequence are associated with significant morbidity and most are not feasible in early gestation. We report the use of an interstitial laser in two pregnancies complicated by this sequence at 14 and 15 weeks, respectively. A 600 microm laser fibre was introduced via a 17 gauge needle into the abdomen of the perfused twin close to the vitelline artery and umbilical vein, which were occluded by neodymium:yttrium aluminium garnet (Nd:YAG) laser. Both pregnancies continued uneventfully and each resulted in the birth of a healthy baby at term.

Freehand three-dimensional Doppler demonstration of monochorionic vascular anastomoses in vivo: a preliminary report

OBJECTIVES

To demonstrate the three-dimensional vascular anatomy of monochorionic placental anastomoses in vivo, both arterioarterial and arteriovenous.

DESIGN

Two-dimensional placental mapping techniques were used to locate arterioarterial and arteriovenous anastomoses. A freehand sweep was performed across the anastomotic site, and multiple images were stored to disk, at 17 Hz. These were then segmented to show only color information (vascular flow) using purpose-designed software (CQ analysis) and the files reconstructed into a three-dimensional volume, for multidirectional viewing and movie generation.

RESULTS

Both arterioarterial and arteriovenous anastomoses could be visualized in detail. Reconstruction of a dual volume of gray-scale and segmented color images allowed recreation of the vascular anatomy within the placental substance, as well as retention of the original directional flow information.

CONCLUSIONS

Detailed anastomotic anatomy can be demonstrated three dimensionally in vivo. Given the increasing evidence implicating various anastomotic configurations in pathological intertwin transfusion, this technique may prove useful in the antenatal assessment and treatment of monochorionic twin pregnancies.

Effect of direct fetal opioid analgesia on fetal hormonal and hemodynamic stress response to intrauterine needling

BACKGROUND

Whether the fetus can experience pain remains controversial. During the last half of pregnancy, the neuroanatomic connections for nociception are in place, and the human fetus mounts sizable stress responses to physical insults. Analgesia has been recommended for intrauterine procedures or late termination, but without evidence that it works. The authors investigated whether fentanyl ablates the fetal stress response to needling using the model of delayed interval sampling during intrahepatic vein blood sampling and transfusion in alloimmunized fetuses undergoing intravascular transfusion between 20 and 35 weeks.

METHODS

Intravenous fentanyl (10 microg/kg estimated fetal weight x 1.25 placental correction) was given once at intrahepatic vein transfusion in 16 fetuses, and changes (posttransfusion - pretransfusion) in beta endorphin, cortisol, and middle cerebral artery pulsatility index were compared with intrahepatic vein transfusions without fentanyl and with control transfusions at the placental cord insertion.

RESULTS

Fentanyl reduced the beta endorphin (mean difference in changes, -70.3 pg/ml; 95% confidence interval, -121 to -19.2; P = 0.02) and middle cerebral artery pulsatility index response (mean difference, 0.65; 95% confidence interval, 0.26-1.04; P = 0.03), but not the cortisol response (mean difference, -10.9 ng/ml, 95% confidence interval, -24.7 to 2.9; P = 0.11) in fetuses who had paired intrahepatic vein transfusions with and without fentanyl. Comparison with control fetuses transfused without fentanyl indicated that the beta endorphin and cerebral Doppler response to intrahepatic vein transfusion with fentanyl approached that of nonstressful placental cord transfusions.

CONCLUSIONS

The authors conclude that intravenous fentanyl attenuates the fetal stress response to intrahepatic vein needling.

Development of three-dimensional power Doppler ultrasound imaging of fetoplacental vasculature

To develop an off-line system for three-dimensional (3-D) ultrasound (US) reconstruction of fetoplacental vasculature using colour segmentation and reconstruction software and to determine sources of error in fully freehand ultrasound image acquisition. US images were acquired freehand with the Acuson Sequoia (5C 2-MHz transducer) using power Doppler. After digital transfer to a personal computer, CQ Analysis software (Kinetic Imaging Ltd, Liverpool, UK) was used to segment the colour information from these images, and the resulting 8-bit grey-scale images were used for 3-D rendering using commercial software (VoxBlast, Vaytek Inc., Fairfield, IA, USA). 2-D scanning, software and freehand acquisition accuracy were assessed using a linear test rig and distance and volume phantoms (Dansk Phantom Service Ltd); 2-D scanning accuracy was within 1.3%, and software reconstruction accuracy within 1% for x and y planes and up to 3% for the z plane. Fully freehand acquisition was associated with a 12% to 18% mean percentage error in distance measurement in the plane of acquisition. Volumetric reconstruction inaccuracy was between 1.5% and 19.7% for precisely separated images and between 16.2% and 39.2% for fully freehand image acquisition. Rendered 3-D US vascular images clearly delineated vascular anatomy within the placenta and cord. Fully freehand 3-D US does have a role in off-line reconstruction of vascular anatomy, although variability in the z plane precludes its use for volumetric measurement. (E-mail: a.welsh@ic.ac.uk)

Perinatal morbidity and mortality rates in severe twin-twin transfusion syndrome: results of the International Amnioreduction Registry

OBJECTIVE

Serial aggressive amnioreduction is the most widely used therapy for pregnancies that are complicated by twin-twin transfusion syndrome. Survival rates reported with this therapy are 33% to 83%, the wide range attributable to the small number of patients in these case series. Similarly, data on morbidity in survivors are imprecise. We instituted the international twin-twin transfusion syndrome registry to determine the perinatal survival and morbidity rates and the factors that influence perinatal outcome in patients with twin-twin transfusion syndrome who were treated with serial aggressive amnioreduction from 1990 to 1998.

STUDY DESIGN

A total of 223 sets of twins who were diagnosed with twin-twin transfusion syndrome before 28 weeks' gestation from 20 fetal medicine referral centers were analyzed, with follow-up data until 4 weeks after birth.

RESULTS

Three hundred forty-six twins (78%; 182 recipients and 164 donors) were born alive. Two hundred sixty-six twins (60%; 144 recipients and 122 donors) were alive 4 weeks after birth. Both fetuses survived to 4 weeks in 108 pregnancies (48.4%), whereas, at least 1 fetus survived in 158 pregnancies (70.8%). The interval between the last amnioreduction and delivery ranged from zero to 138 days (median, 17.5 days). In the infants who survived to 4 weeks after birth, abnormalities on neonatal cranial scan were diagnosed in 24% of recipients and in 25% of donors. Logistic regression analysis indicated that the survival rate was significantly related to gestational age at diagnosis, presence of end-diastolic blood flow in the umbilical artery velocity waveforms, presence of hydrops, mean volume of amniotic fluid removed per week, larger birth weight, and gestational age at delivery. The hemoglobin level difference at birth was the only significant parameter to predict abnormal cranial ultrasonography in newborns.

CONCLUSION

These data document perinatal survival and neonatal morbidity rates in severe twin-twin transfusion syndrome that were treated by serial aggressive amnioreduction. Outcome was influenced by several perinatal risk factors, which may be used to counsel patients before and during therapy.

Umbilical cortisol levels as an indicator of the fetal stress response to assisted vaginal delivery

OBJECTIVES

While it is well established that delivery by elective caesarean section is less stressful for the fetus than normal vaginal delivery, little attention has been paid to the effect on the baby of an assisted delivery.

STUDY DESIGN

We examined cortisol levels in venous cord blood from seven babies born by forceps, 10 by ventouse extraction, 28 by unassisted normal vaginal delivery, and 12 born by elective caesarean. Paired maternal bloods were taken immediately after delivery.

RESULTS

Cord blood cortisol values were significantly different in the different groups (one-way ANOVA, P < 0.0001). The forceps group had the highest values and the caesarean group the lowest; both were different from the normal vaginal delivery group (P=0.019 and P=0.046, respectively). There was no effect of length of labour, or method of pain relief on cortisol levels. Maternal values were similar in the different groups, confirming that the differences observed derived from the fetus.

CONCLUSIONS

There is increasing evidence that the stress experienced by the fetus or neonate can have long-term effects on the function of the hypothalamic-pituitary-adrenal axis in later life. We speculate that the stress caused by some assisted deliveries may contribute to this.

Maternal stress in pregnancy and its effect on the human foetus: an overview of research findings

There is evidence from human studies that anxiety or stress during pregnancy can affect birth outcome, causing babies to be born earlier and possibly smaller for gestational age. There is also some suggestive evidence for longer-term behavioural problems. Animal studies indicate that antenatal stress does have a long-term effect on the behaviour of the offspring, including a hyper-responsive hypothalamo-pituitary -adrenal axis. The human foetus can mount an independent stress response from mid-gestation. Two possible mechanisms have been demonstrated by which maternal stress or anxiety may affect the human foetus, the passage of cortisol across the placenta, and an impairment of blood flow through the maternal uterine arteries.

Simultaneous fetal cell identification and diagnosis by epsilon-globin chain immunophenotyping and chromosomal fluorescence in situ hybridization

Isolating fetal erythroblasts from maternal blood offers a promising noninvasive alternative for prenatal diagnosis. The current immunoenzymatic methods of identifying fetal cells from background maternal cells postenrichment by labeling gamma-globin are problematic. They are nonspecific because maternal cells may produce gamma-globin, give poor hybridization efficiencies with chromosomal fluorescence in situ hybridization (FISH), and do not permit simultaneous visualization of the fetal cell identifier and the FISH signal. We describe a novel technique that allows simultaneous visualization of fetal erythroblast morphology, chromosomal FISH, and epsilon-globin labeled with AMCA (7-amino-4-methylcoumarin-3-acetic acid). AMCA was chosen as the fluorescent label to circumvent the problem of heme autofluorescence because the mean difference in relative fluorescence intensity between fetal erythroblasts stained positive for antiglobin antibody and autofluorescence of unstained cells was greater with AMCA (mean 43.2; 95% confidence interval [CI], 34.6-51.9; SD = 14.0) as the reporting label compared with fluorescein isothiocyanate (mean 24.2; 95% CI, 16.4-31.9; SD = 12.4) or phycoerythrin (mean 9.8; 95% CI, 4.8-14.8; SD = 8.0). Median FISH hybridization efficiency was 97%, comparable to the 98% (n = 5 paired samples) using Carnoy fixative. One epsilon-positive fetal erythroblast was identified among 10(5) maternal nucleated cells in 6 paired mixture experiments of fetal erythroblasts in maternal blood (P <.001). Male epsilon-positive fetal erythroblasts were clearly distinguishable from adult female epsilon-negative erythroblasts, with no false positives (n = 1000). The frequency of fetal erythroblasts expressing epsilon-globin declines linearly from 7 to 14 weeks' gestation (y = -15.8 x + 230.8; R(2) = 0.8; P <.001). We describe a rapid and accurate method to detect simultaneously fetal erythroblast morphology, intracytoplasmic epsilon-globin, and nuclear FISH. (Blood. 2001;98:554-557)

Obstetricians say yes to maternal request for elective caesarean section: a survey of current opinion

AIM

To determine what proportion of obstetricians would agree to elective pre-labour CS for 'maternal request'.

METHODS

Every fifth consultant on an alphabetical list of obstetricians in England and Wales obtained from the RCOG (243) was surveyed by post and asked (a) "Would you agree to perform an elective CS on a woman with an uncomplicated singleton cephalic pregnancy at term for 'maternal request?"' and (b) if yes, in relation to this 'Has your practice changed over recent years?"

RESULTS

155 questionnaires were returned (63% response rate -- four unanswered, leaving 151 for analysis). One hundred and four (69%) consultants said they would agree to 'maternal request' for CS. Of the 'yes' respondents, 62 (60%) claimed their practice had changed recently.

CONCLUSION

This survey demonstrates that a majority of obstetricians are now prepared to agree to maternal request for CS in the absence of obstetric indications.

Twin-to-Twin Transfusion Syndrome Results From Dynamic Asymmetrical Reduction in Placental Anastomoses: A Hypothesis

Although placental vascular anastomoses between the fetoplacental circulations are ubiquitous in monochorionic twin pregnancies, the factors regulating their formation and maintenance are not understood. Increasing evidence implicates asymmetric anastomotic patterns in the aetiology of severe twin-to-twin transfusion syndrome (TTTS). The authors propose that anastomoses between placental circulations in monochorionic twins occur in a random manner at the embryological stage of connection of embryonic and extra-embryonic circulations. Placental expansion is then associated with random disruption of anastomoses and regression of their associated villus districts. TTTS develops as discordant loss of anastomoses results in asymmetrical flow resistance. Pregnancies with fetal growth concordance but discordant nuchal translucency at 10-14 weeks are at increased risk of developing subsequent severe TTTS because these clinical features indicate significant pressure differentials in the presence of a placentoplacental circulation, consistent with the presence of numerous, asymmetric anastomoses. However, since the anastomotic pattern is dynamic in the first half of pregnancy this hypothesis predicts that it will not be possible to devise a clinical test at 12 weeks that will predict with certainty the outcome of monochorionic twin pregnancies in relation to TTTS because this depends on random subsequent events.

Intrauterine rescue transfusion in monochorionic multiple pregnancies with recent single intrauterine death

To assess the role of fetal blood sampling and intrauterine transfusion in monochorionic (MC) multiple pregnancy complicated by single intrauterine death (IUD), we reviewed ten cases over a 4-year period in a tertiary referral centre which underwent fetal blood sampling within 24 h of death of its MC co-twin. Intrauterine rescue transfusion was performed in all seven anaemic fetuses (hematocrit; Hct < 30%) to raise the fetal Hct to > or = 40%. The rationale was to prevent death and/or brain injury. Two fetuses, which were severely acidaemic at blood sampling, died in utero within 24 h of the procedure. In two cases, the surviving twins manifested abnormal sonographic findings of the fetal brain 2-5 weeks later and underwent late termination. In two cases, the pregnancies continued uneventfully until delivery at 35 and 40 weeks' gestation with good neonatal outcome. In one case the co-twin delivered 1 week later at 29 weeks but died within 12 h. Fetuses without anaemia were not transfused and had normal clinical outcomes. We suggest that intrauterine rescue transfusion before the development of severe acidaemia in anaemic surviving MC co-twins may prevent fetal death, but does not necessarily prevent brain injury. Until its role becomes clearer, we recommend that its use be restricted to situations in which the parents and the local jurisdiction allow late termination as an option if brain injury subsequently manifests on ultrasound.

Quantitative digital analysis of regional placental perfusion using power Doppler in placental abruption

PURPOSE

To apply digital imaging techniques to the quantification of placental vascularity using power Doppler.

MATERIALS AND METHODS

Regional placental blood flow was measured in a case of large placental abruption, shortly after presentation and 1 week later. Images were stored digitally and analysed using purpose-designed software (CQ Analysis) to extract and measure vascular energy information. The integrated color energy (ICE) was determined in the main body of placental tissue and in a cotyledon isolated by the retroplacental clot.

RESULTS

Initial assessment at 25 weeks showed only a small difference in integrated energy between normal placenta and the isolated cotyledon (ICE ratio 1.44, P < 0.04). One week later, perfusion in the isolated cotyledon had fallen both on qualitative and quantitative assessment (ICE ratio 3.98, P < 0.0001). This area subsequently became devascularized.

CONCLUSION

Placental perfusion may be quantified using digital power Doppler analysis. Further studies are indicated to evaluate its role in assessing regional and/or global placental perfusion as well as fetal organ perfusion.

Fetal hypothalamic-pituitary-adrenal stress responses to invasive procedures are independent of maternal responses

Paired fetal and maternal samples were obtained, at fetal blood sampling and intrauterine transfusion, to study hypothalamic-pituitary-adrenal stress responses. This confirmed that the fetus mounts an hypothalamic-pituitary-adrenal stress response to transfusion via the intrahepatic vein, which involves piercing the fetal trunk, but not to transfusion via the placental cord insertion [mean cortisol response via intrahepatic vein delta = 52.6 nmol/L, 95% CI (25.3-79.9), P = 0.001; mean beta-endorphin response delta =106 pg/mL, 95% CI (45.3-167), P = 0.002]. Baseline maternal fetal ratios were 13 [95% CI (10.7-15.2)] for cortisol and 0.8 [95% CI (0.5-1.0)] for beta-endorphin. The novel findings were: 1) that the fetal responses were independent of those of the mother, which did not change during transfusion at either site; 2) that there was a correlation between baseline fetal and maternal cortisol levels (r = 0.58, n = 51, P < 0.0001) but not between baseline fetal and maternal ss-endorphin levels, suggesting cortisol transfer across the placenta, rather than joint control by placental CRH; and 3) that fetal beta-endorphin responses were apparent from 18 weeks gestation and independent of gestational age, whereas fetal cortisol responses were apparent from 20 weeks gestation and were dependent on gestational age (y = -91.4 + 5.08x, r = 0.51; n = 16; P = 0.04; CI for slope, 0.16-10.0), consistent with the maturation of the fetal pituitary before the fetal adrenal.

Antenatal factors at diagnosis that predict outcome in twin-twin transfusion syndrome

OBJECTIVE

We sought to identify clinical factors at diagnosis that predict outcome in twin-twin transfusion syndrome.

STUDY DESIGN

In this retrospective series 23 patients with twin-twin transfusion syndrome were seen in a tertiary referral fetal medicine center over a 3-year period. Ten antenatal factors were assessed to determine their ability to predict outcome by use of ordered logistic regression. These factors were the following: (1) absent or reversed end-diastolic flow in the umbilical artery, nonvisible bladder, anhydramnios, and estimated fetal weight of <3rd percentile in the donor; (2) pulsatile umbilical vein, either absent or reversed end-diastolic flow in the ductus venosus, or both, and tricuspid-mitral valve regurgitation in the recipient; and (3) gestational age at presentation, estimated fetal weight discordancy, absent arterioarterial anastomosis, and spontaneous rupture of the membranes or cervical change as pregnancy factors. Management comprised serial amnioreduction (n = 10), selective feticide (n = 5; 4 also had amnioreduction), septostomy (n = 4; 1 also had amnioreduction), and delivery (n = 2). Two patients miscarried before treatment.

RESULTS

The chance of survival of both twins fell and double deaths increased linearly with increasing number of adverse factors (P =.026). A low chance of survival was independently associated with absent or reversed end-diastolic flow in the donor umbilical artery (P =.02) and with a pulsatile umbilical vein or absent or reversed end-diastolic flow in the ductus venosus (P =.03) of the recipient. The probability of at least one twin surviving was only 33% if there was absent or reversed end-diastolic flow in the donor umbilical artery or 37% when abnormal venous recordings were seen in the recipient. An arterioarterial anastomosis detected at diagnosis also influenced prognosis, with all twins surviving when an arterioarterial anastomosis was identified (P =.04).

CONCLUSIONS

Three factors identified at diagnosis independently predict poor survival in twin-twin transfusion syndrome-absent or reversed end-diastolic flow in the donor umbilical artery, abnormal pulsatility of the venous system in the recipient, and absence of an arterioarterial anastomosis. These may have a role in the counseling of parents and in selecting the appropriate treatment strategy.

Identification of arterio-venous anastomoses in vivo in monochorionic twin pregnancies: preliminary report

OBJECTIVE

To determine whether it is possible to identify in vivo placental arterio-venous anastomoses (AVAs) by color Doppler flow mapping.

METHODS

Three monochorionic twin pregnancies (one with and two without twin-to-twin transfusion syndrome) underwent placental mapping by color Doppler ultrasound. Placental vessels along the chorionic plate were recorded together with the direction of blood flow and their location in relation to the cord insertions and to superficial arterio-arterial anastomoses. Suggestive AVAs were mapped topographically and results were compared with the findings of formal postnatal placental injection studies.

RESULTS

An AVA was identified in each of the three cases. Injection studies showed multiple AVAs. Each antenatally identified AVA was confirmed at placental injection study. Their placental location correlated to other landmarks as predicted by ultrasound.

CONCLUSIONS

This preliminary report demonstrates that AVAs can be identified using color Doppler ultrasound. This may facilitate planning for highly selective ablation of AVAs, and shorter procedure times. Formal studies are now indicated to determine the accuracy of this technique.

Pain and stress in the human fetus

Invasive diagnostic and therapeutic techniques are increasingly applied to the fetus. It is not known if the fetus feels pain during such procedures, but the fetus does mount significant stress hormonal and circulatory changes in response to these from 18-20 weeks. Perinatal stress may have long-term neurodevelopmental implications. During open fetal surgery, maternal general anaesthesia provides fetal anaesthesia. However, in closed procedures, fetal analgesia presents difficulties. The optimal drug, dose, and route of administration remain to be determined.

Clinical outcome of congenital talipes equinovarus diagnosed antenatally by ultrasound

Congenital talipes equinovarus is a common anomaly which can now be diagnosed prenatally on a routine ultrasound scan at 20 weeks of gestation. Prenatal counselling is increasingly offered to parents with affected fetuses, but it is difficult to counsel parents if there is a chance that the fetus may not have talipes. Our study correlates the prenatal ultrasound findings of 14 infants diagnosed as having unilateral or bilateral talipes during their routine 20-week ultrasound scan with their clinical findings at birth and the treatment received. No feet diagnosed as talipes on the ultrasound scan were completely normal at birth and therefore there were no true false-positive results. One foot graded as normal at 20 weeks was found to have a mild grade-1 talipes at birth, but did not require treatment other than simple stretches. A total of 32% of feet required no treatment and so could be considered functional false-positive results on the scan. Serial casting was required by 13% of feet and surgical treatment by 55%. The severity of the talipes is difficult to establish before birth. A number of patients are likely to need surgical treatment, but a proportion will have talipes so mildly that no treatment will be required. In counselling parents at 20 weeks, orthopaedic surgeons need to know whether or not there is a small chance that the ultrasound diagnosis could be wrong and also that the talipes may be so mild that the foot will not require treatment.

Clinical outcome of congenital talipes equinovarus diagnosed antenatally by ultrasound

Congenital talipes equinovarus is a common anomaly which can now be diagnosed prenatally on a routine ultrasound scan at 20 weeks of gestation. Prenatal counselling is increasingly offered to parents with affected fetuses, but it is difficult to counsel parents if there is a chance that the fetus may not have talipes. Our study correlates the prenatal ultrasound findings of 14 infants diagnosed as having unilateral or bilateral talipes during their routine 20-week ultrasound scan with their clinical findings at birth and the treatment received.

No feet diagnosed as talipes on the ultrasound scan were completely normal at birth and therefore there were no true false-positive results. One foot graded as normal at 20 weeks was found to have a mild grade-1 talipes at birth, but did not require treatment other than simple stretches. A total of 32% of feet required no treatment and so could be considered functional false-positive results on the scan. Serial casting was required by 13% of feet and surgical treatment by 55%. The severity of the talipes is difficult to establish before birth. A number of patients are likely to need surgical treatment, but a proportion will have talipes so mildly that no treatment will be required. In counselling parents at 20 weeks, orthopaedic surgeons need to know whether or not there is a small chance that the ultrasound diagnosis could be wrong and also that the talipes may be so mild that the foot will not require treatment.

Prenatal diagnosis in multiple pregnancy

Fetal abnormality is more common in multiple than in singleton pregnancies. This, together with the requirement to consider the risks with at least two babies to sample correctly each fetus and to undertake accurately-targeted selective termination, amounts to a major challenge for obstetricians involved in prenatal diagnosis. Early determination of chorionicity should be routine, since this influences not only the genetic risks but also the invasive procedure chosen for karyotyping or genotyping. Assessment of nuchal translucency identifies individual fetuses at risk of trisomy. Contrary to expectation, invasive procedures in twins appear to have procedure-related miscarriage rates that are similar to those in singletons. Instead, contamination remains a concern at chorionic villus sampling. Elective late karyotyping of fetuses may have a role in some countries. Whereas management options for discordant fetal abnormality are relatively straightforward in dichorionic pregnancies, monochorionic pregnancies are at risk of co-twin sequelae after any single intrauterine death. Techniques have now been developed to occlude completely the cord vasculature by laser and/or ultrasound guided bipolar diathermy. Given the complexities associated with prenatal diagnosis, all invasive procedures in multiple pregnancies should be performed in tertiary referral centres.

Doppler detection of arterio-arterial anastomoses in monochorionic twins: feasibility and clinical application

The accuracy of in-vivo detection of arterio-arterial anastomoses (AAA) in monochorionic (MC) twins and its predictive value for twin-twin transfusion syndrome (TTTS) was assessed in 105 consecutive MC twins scanned at fortnightly intervals. AAA were sought using spectral and colour energy Doppler and ultrasound findings were compared with placental injection studies. AAA were identified in vivo in 59 (56%) pregnancies and at injection study in 68 (65%). The overall sensitivity and specificity was 85 and 97.3% respectively for the detection of AAA. Detection rates were higher at later gestations, with anterior placentae and with larger diameter AAA. The median insonation time to detect an AAA was 10 min (range 1-30). Where an AAA was identified, 15% of pregnancies (nine of 59) developed TTTS compared to 61% (28 of 46) when no AAA was seen (odds ratio 8.6). We conclude that AAA can be detected in vivo with high sensitivity and specificity without undue prolongation of scanning times and have a role in risk stratification in the antenatal assessment of MC twins.

Ex vivo delineation of placental angioarchitecture with the microbubble contrast agent Levovist

OBJECTIVE

The aim of this study was to delineate placental vasculature with the microbubble contrast agent Levovist (99.9% galactose and 0.1% palmitic acid; Schering AG, Berlin, Germany), with the ultimate goal of delineating placental vascular anatomy in utero.

STUDY DESIGN

A placental lobule from each of 11 term human placentas was perfused on the fetal side of the circulation under physiologic conditions. Randomly assigned dose-concentration combinations of Levovist were administered through a chorionic artery into the corresponding placental lobule, and the resultant echoenhancement with power Doppler imaging was recorded for digital analysis. Interplacental variability was corrected for by averaging the results of three injections at each dose-concentration combination.

RESULTS

Echoenhancement was seen at all dose-concentration combinations in the injected lobule but not in adjacent control lobules. The three dose-concentration combinations that achieved optimal maximal integrated intensity and duration of action for both chorionic vessel and villus enhancement were 100 microL/kg of 400-mg/mL Levovist, 200 microL/kg of 400-mg/mL Levovist, and 400 microL/kg of 200-mg/mL Levovist.

CONCLUSION

Microbubble contrast injection into the fetal vasculature enabled power Doppler imaging echoenhancement both in chorionic vessels and within the villus tree. We speculate that fetal injection of contrast agent may be applied to the delineation of placental lesions or areas of interfetal transfusion, although its applicability will be hindered by the need for fetal blood sampling.

Fetal origins of reduced arterial distensibility in the donor twin in twin-twin transfusion syndrome

Twin-twin transfusion syndrome permits investigation of vascular programming independent of genetic influence. Arterial distensibiity was lower in the donor twin during infancy, implying the intrauterine vascular remodelling might result in raised cardiac afterload and could influence later cardiovascular health.

Maternal contamination at fetal muscle biopsy

Duchenne muscular dystrophy (DMD) can be diagnosed by fetal muscle biopsy and immunohistochemical staining showing the absence of dystrophin. We report a case of fetal muscle biopsy in which the needle gun was successfully fired within the fetal gluteal muscle but the sample was contaminated by maternal tissue. This was attributed to the design of the biopsy needle, allowing transient opening of the biopsy core as the needle penetrated the maternal rectus sheath, muscle, and myometrium. Histology showed tissue suggestive of maternal origin, confirmed by DNA analysis. Repeat sampling revealed fetal muscle with normal dystrophin expression. We recommend that care be taken during needle insertion to avoid maternal contamination, and tests be used to confirm the fetal source of the sample.

Twin fetuses: intravascular microbubble US contrast agent administration--early experience

PURPOSE

To explore the feasibility of administering SH U 508A by using a single-needle procedure at ultrasonography (US) in twin pregnancies to confirm interfetal transfusion in monochorionic twins and delineate placental angioarchitecture in pregnancies with twin-twin transfusion syndrome.

MATERIALS AND METHODS

Fourteen twin pregnancies were studied over 12 months: seven with monochorionic twins, including six with twin-twin transfusion syndrome; two of unknown chorionicity; and five with known dichorionic twins discordant for fetal karyotype or anomaly and undergoing selective feticide in the third trimester. Bolus injection of 100 microL/kg of estimated fetoplacental weight of 400 mg/mL of SH U 508A was performed in the intrahepatic vein of one twin, and evidence of interfetal transfusion was sought by means of digital analysis of power Doppler signals in the contralateral twin.

RESULTS

Contralateral twin echo enhancement was seen in four of the nine ultimately histopathologically proved monochorionic twins. As expected, no evidence of echo enhancement in the contralateral twin was seen in any of the five dichorionic twin pregnancies. There was no evidence of fetal compromise associated with the procedure.

CONCLUSION

These pilot results suggest that microbubbles can be used to demonstrate interfetal transfusion but not to delineate placental vascular anatomy.

Middle cerebral artery peak systolic velocity in the prediction of fetal anemia

OBJECTIVE

The fetal middle cerebral artery peak systolic velocity (MCA PSV) has been suggested as a potential test to predict the fetal hematocrit level. We tested the hypothesis that a low fetal hematocrit is associated with an increase in MCA PSV in a prospective study of normal and alloimmunized pregnancies.

METHODS

Fetal hematocrit and MCA PSV were obtained in 26 alloimmunized fetuses, immediately before their first fetal blood transfusions between 15 and 35 weeks. Results were compared with the MCA PSVs from 170 control fetuses not at risk of alloimmune anemia between 13 and 37 weeks.

RESULTS

In control fetuses, PSV varied with gestation (PSV = 0.56 - 0.032 GA + 0.00086 GA2, where GA is gestational age; R2 = 0.41). The correlation between PSV and hematocrit Z scores (Pearson correlation coefficient r = -0.69) was highly significant (P = 0.0001). Using a PSV > 1 SD, the sensitivity of the test in predicting a fetal hematocrit < 2 SD below the mean was only 64% but the specificity was 100%. However, the sensitivity of the test in predicting a fetal hematocrit < 3 SD and < 4 SD rose to 73% and 83%, while the specificity was still good (93% and 80% respectively).

CONCLUSIONS

MCA PSV and fetal hematocrit are highly significantly correlated. The sensitivity of the test was good and the high positive predictive value indicates that the presence of a raised PSV (defined as > 1 SD) is a strong indicator of fetal anemia. In conclusion, MCA PSV is a useful test in clinical practice for the detection of fetal anemia.

High sensitivity of fetal DNA in plasma compared to serum and nucleated cells using unnested PCR in maternal blood

DNA analysis of blood is conventionally performed on cells - plasma and serum are discarded. Free DNA has been demonstrated in serum in cancer and autoimmune disorders and in pregnancy. We investigated possible noninvasive prenatal diagnosis using fetal DNA from maternal plasma and serum in pregnancy. Fetal gender was determined by PCR on DNA from maternal venous blood, serum and plasma of 65 women by boiling with or without phenol/chloroform extraction. When sensitivities were compared for plasma, additional phenol/chloroform extraction proved more sensitive than boiling alone (89 vs. 50%), the observed difference was 50% (CI 19 to 81%). Extracted plasma amplified better than extracted serum (89 vs. 46%), the observed difference being 44% (CI 22 to 66%). In contrast, fetal gender could not reliably be determined from DNA extracted from maternal nucleated blood cells. The size of plasma and serum DNA at 15-17 weeks of gestation was >1,500 bp. This work confirms the presence of fetal DNA in maternal plasma and serum which may be applicable to noninvasive prenatal diagnosis of paternally derived DNA sequences. We conclude that optimal sensitivity requires two methods of DNA extraction and that the use of plasma is preferred to that of serum.

Preclinical development of noninvasive vascular occlusion with focused ultrasonic surgery for fetal therapy

OBJECTIVE

This study was undertaken to investigate the ability of focused ultrasonic surgery to occlude blood flow in vivo.

STUDY DESIGN

A 5-mm linear track exposure of 1.7-MHz focused ultrasound was applied across the femoral vessels for 5 seconds. Free field spatial peak intensities in the range of 1,000 to 4,660 W x cm(-2) were used. Vascular occlusion was confirmed after demonstration of an absent distal arterial pulse and an absent flow signal on magnetic resonance angiography and subtracted (after minus before) contrast-enhanced dual-echo steady-state sequences.

RESULTS

The minimum intensity for consistent vascular occlusion was 1,690 W x cm(-2) at a focal depth of 5 mm when the transducer was moved at 1 mm x s(-1) orthogonal to the direction of blood flow.

CONCLUSIONS

This study demonstrates that focused ultrasonic surgery can achieve reproducible vascular occlusion in vivo. Potential obstetric applications include noninvasive ultrasonographically guided occlusion of placental vessels mediating interfetal transfusion in monochorionic twins.

Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome

OBJECTIVE

We sought to correlate placental vasculature with fetal growth and outcome in monochorionic twins.

STUDY DESIGN

Eighty-two patients with consecutive monochorionic pregnancies underwent biweekly ultrasonography for determination of fetal growth and well-being. After delivery, blinded placental injection studies delineated vascular anastomoses and territory share. Degree of balance in arteriovenous anastomoses equaled the number of arteriovenous anastomoses in one direction minus the number in the other.

RESULTS

Pregnancies affected by fetofetal transfusion syndrome (n = 21) had numbers of arteriovenous and venovenous anastomoses that were similar to those in pregnancies without fetofetal transfusion syndrome but fewer arterioarterial anastomoses (P <.0001). Fetofetal transfusion syndrome occurred in 78% of pregnancies with >/=1 arteriovenous and no arterioarterial anastomoses. Birth weight discordancy correlated with placental territory discordancy (P <.0001) and the degree of balance in arteriovenous anastomoses (P =.004). The larger placental share twin had a greater growth velocity than its smaller placental share co-twin (P =.008) for all but one anastomotic pattern. Where arteriovenous anastomoses were aligned with the net venous outflow to the fetus with the smaller territory, co-twins had similar birth weights and growth velocities irrespective of placental share. Fetal survival was higher in pregnancies with an arterioarterial anastomosis (P =.01) but lower with a venovenous anastomosis (P =. 01). Survival of both fetuses was inversely associated with birth weight discordancy (P <.0001).

CONCLUSION

Although interrelationships among the various types of anastomoses are complex, our data suggest that the placental territory share and the pattern of arteriovenous anastomoses influence fetal growth, that arterioarterial anastomoses protect against fetofetal transfusion syndrome, and that venovenous anastomoses reduce perinatal survival.

Mode of delivery and subsequent stress response

We have shown that a baby's stress (saliva cortisol) and crying response to inoculation at 8 weeks was related to mode of delivery, with the greatest response shown in those born by assisted delivery and the least response in those born by elective caesarean section.

Acute cerebral redistribution in response to invasive procedures in the human fetus

OBJECTIVES

We sought to investigate the fetal hemodynamic response to the acute stress of invasive procedures.

STUDY DESIGN

The middle cerebral artery pulsatility index was measured by Doppler ultrasonography before and after 136 invasive procedures (fetal blood sampling, transfusion, shunt insertion, tissue biopsy, and ovarian cyst aspiration). The response of fetuses submitted to invasive procedures involving transgression of the fetal body, such as intrahepatic vein blood sampling, was compared with that of control procedures at the placental cord insertion.

RESULTS

The middle cerebral artery pulsatility index value fell with fetal blood sampling performed at the intrahepatic vein (median, -0.26; 95% confidence interval, -0.35 to -0.15) but not at the placental cord insertion (median, 0.05; 95% confidence interval, -0.04 to 0.19). With transfusions, the middle cerebral artery pulsatility index also fell with procedures at the intrahepatic vein (mean, -0.51; 95% confidence interval, -0.66 to -0.35) but not at the placental cord insertion (mean, -0.04; 95% confidence interval, -0.23 to 0.14). The magnitude of the response was greater with transfusions than with blood sampling alone. The middle cerebral artery pulsatility index value also fell with non-fetal blood sampling procedures involving transgression of the fetal body (mean, -0.32; 95% confidence interval, -0.56 to -0.09) but not with control non-fetal blood sampling procedures. The change in the middle cerebral artery pulsatility index was not related to gestational age, with the youngest fetus showing a fall in the middle cerebral artery pulsatility index value being at 16 weeks' gestation. Although the degree of response was weakly correlated with the duration of needling (y = -0.21 - 0.00014x; R (2) = 0.08; P =.02), multiple logistic regression demonstrated that this was instead a function of the type of the procedure. A response was seen within 70 seconds of fetal puncture. The fetal heart rate did not change significantly with procedures in any of the above-mentioned groups.

CONCLUSIONS

The human fetus mounts a cerebral hemodynamic response to invasive procedures involving transgression of the fetal body, which is consistent with the brain-sparing effect.

High failure rate of umbilical vessel occlusion by ultrasound-guided injection of absolute alcohol or enbucrilate gel

The success rate for injected umbilical vascular occlusion in the published literature exceeds 85 per cent. In this study we assessed the efficacy of two forms of injected sclerosants in achieving umbilical vessel occlusion. 12 cases of attempted ultrasound-guided occlusion over a 2 1/2 year period were reviewed. These were monochorionic (MC) twins (n=6), dichorionic twins (n=3) and singletons (n=3) undergoing fetocide for severe anomalies, or impending fetal demise. Absolute alcohol (n=6), enbucrilate gel (n=5) or both (n=1) were used in an attempt to achieve vascular occlusion. Complete vessel occlusion was achieved in only a third of cases (4/12), three with absolute alcohol and one with enbucrilate gel. In MC twins occlusion was successful in two of six cases. In contrast to previously published data, this large series, containing more cases than the total previously reported, shows considerably poorer success rates for injected umbilical vascular occlusion. Injection of currently available sclerosants can no longer be recommended for umbilical vascular occlusion in human fetuses.

Endothelin concentrations in monochorionic twins with severe twin-twin transfusion syndrome

The objective of this study was to determine endothelin (ET-1) concentrations in monochorionic twin fetuses with and without twin-twin transfusion syndrome (TTTS). Fourteen monochorionic twin pregnancies complicated by TTTS and six without TTTS were studied. Matched maternal and fetal blood samples were obtained both in utero and at birth. Amniotic fluid samples were also collected from twin pairs. ET-1 concentrations were measured by radio-immunoassay. ET-1 concentrations in recipient fetuses were higher than in the donors both in utero(P < 0.001) and at birth (P < 0.01). Fetal concentrations of ET-1 in donors were similar to non-TTTS twins. Plasma ET-1 concentrations were significantly higher (P < 0.01) in recipient fetuses with severe hydrops than those with mild/no hydrops. Maternal concentrations of ET-1 were comparable in the two groups. Endothelin concentrations in recipient twins were 2(1/2) times higher than in their co-twins and this was related to the severity of hydrops.

Vascular occlusion using focused ultrasound surgery for use in fetal medicine

OBJECTIVE

Focused ultrasound surgery (FUS) is being developed clinically for the non-invasive treatment of soft tissue tumours of the prostate, bladder, liver, kidney, muscle and breast. In the work described in this paper, the application of FUS is extended to investigate the potential to induce vascular occlusion, with the aim of applying the technique to problems in fetal medicine and oncology.

METHODS

In this feasibility study the occlusion of femoral blood flow in vivo is demonstrated using an array of multiple single exposures of 1.7 MHz focused ultrasound. These were placed in two rows of four lesions at a focal depth of 5 mm. The 4660-W cm-2 (free field spatial peak intensity) 2-s exposures were placed 2 mm apart. Vascular patency was assessed using a Siemens Vision (1.5T) magnetic resonance (MR) imaging scanner with an extremity coil, and intravenous gadolinium contrast agent. FLASH and FISP MR sequences were used to obtain full 3D data sets providing information on soft tissue damage and perfusion.

RESULTS AND CONCLUSION

Total vascular occlusion was achieved in four of nine cases and significant vascular disruption in five of nine cases. Refinement of the FUS technique and long-term studies are now indicated prior to initial clinical application in fetal medicine.

First-trimester cord entanglement in monoamniotic twins

OBJECTIVE

Monoamniotic twinning occurs in only 1% of twin pregnancies, but carries a high perinatal mortality rate. Early and reliable diagnosis is essential if attempts are to be made to reduce the complication rate. We report color Doppler demonstration of cord entanglement in the first trimester, which is diagnostic of monoamnionicity.

METHODS

Two patients with twin pregnancies were examined in the first trimester with pulsed and color Doppler insonation of their umbilical arteries.

RESULTS

Cord entanglement was suspected and proved by demonstrating differing fetal heart rate patterns in the same direction on umbilical artery Doppler analysis of a common mass of cord vessels. Following appropriate counselling, medical amnioreduction was induced at 20 weeks of gestation to reduce fetal movements and worsening cord entanglement. Delivery was by elective Cesarean section at 32 weeks' gestation and monoamnionicity was confirmed.

CONCLUSION

We report a new sign for the demonstration of monoamnionicity in twin pregnancies in the first trimester. This should improve the reliability of early diagnosis, but further studies are required to confirm that, if cord entanglement occurs, it is usually present by the end of the first trimester.

Association between maternal anxiety in pregnancy and increased uterine artery resistance index: cohort based study

OBJECTIVE

To investigate whether maternal anxiety in the third trimester is associated with an increased uterine artery resistance index.

DESIGN

Cohort based study.

SUBJECTS

100 pregnant women, with a mean gestation of 32 weeks.

OUTCOME MEASURES

Self rating Spielberger questionnaire for state anxiety and trait anxiety, and uterine blood flow waveform patterns as assessed by colour Doppler ultrasound.

RESULTS

A significant association was found between uterine artery resistance index and scores for both Spielberger state anxiety and trait anxiety (rs=0.31, P<0.002 and 0.28 P<0.005 respectively). Women with state anxiety scores >40 (n=15) had a higher mean uterine resistance index than those with scores </= 40 (mean difference with mean resistance index 24%, 95% confidence interval 12% to 38%; P<0.0001). Similarly, women with trait anxiety scores >40 (n=32) had a higher mean resistance index than those with scores </= 40, although to a lesser extent. The presence of notches in the waveform pattern produced by uterine artery blood flow was found in 4/15 (27%) women with high state anxiety scores compared with 4/85 (5%) with low anxiety scores (P<0.02).

CONCLUSIONS

This study shows an association between maternal anxiety in pregnancy and increased uterine artery resistance index. It suggests a mechanism by which the psychological state of the mother may affect fetal development, and may explain epidemiological associations between maternal anxiety and low birth weight. The influence of maternal anxiety may be one mechanism by which the intrauterine environment contributes to later disease in offspring.

X-chromosome inactivation patterns do not implicate asymmetric splitting of the inner cell mass in the aetiology of twin-twin transfusion syndrome

The aetiology of twin-twin transfusion syndrome (TTTS) is unclear. We investigated the hypothesis that monochorionic (MC) pregnancies with TTTS are associated with differences in the timing and symmetry of twinning compared to MC twin pregnancies without TTTS. DNA was extracted from the umbilical cord vessels of 26 female MC twins, 14 with and 12 without TTTS on serial antenatal ultrasound. X-inactivation patterns were determined by DNA digestion with Hhal and Hpall followed by polymerase chain reaction for a polymorphic trinucleotide repeat in the androgen receptor gene. Products were quantified by densitometry and results compared to those in peripheral blood samples of adult female controls. The median degree of non-random inactivation was similar in MC twins with TTTS, in MC twins without TTTS, and in adult controls. The percentage of individuals with skewed (> or =30/70%) inactivation patterns was no different in MC twins with TTTS compared to those without TTTS, and was similar to adult controls using either enzyme technique. In conclusion we found no difference in the degree or frequency of non-random X-inactivation patterns in TTTS. X-inactivation patterns do not appear to be a useful tool for studying the symmetry of inner cell mass splitting in monochorionic twins.

Randomised trial of educational visits to enhance use of systematic reviews in 25 obstetric units

OBJECTIVE

To evaluate the effectiveness of an educational visit to help obstetricians and midwives select and use evidence from a Cochrane database containing 600 systematic reviews.

DESIGN

Randomised single blind controlled trial with obstetric units allocated to an educational visit or control group.

SETTING

25 of the 26 district general obstetric units in two former NHS regions.

SUBJECTS

The senior obstetrician and midwife from each intervention unit participated in educational visits. Clinical practices of all staff were assessed in 4508 pregnancies.

INTERVENTION

Single informal educational visit by a respected obstetrician including discussion of evidence based obstetrics, guidance on implementation, and donation of Cochrane database and other materials.

MAIN OUTCOME MEASURES

Rates of perineal suturing with polyglycolic acid, ventouse delivery, prophylactic antibiotics in caesarean section, and steroids in preterm delivery, before and 9 months after visits, and concordance of guidelines with review evidence for same marker practices before and after visits.

RESULTS

Rates varied greatly, but the overall baseline mean of 43% (986/2312) increased to 54% (1189/2196) 9 months later. Rates of ventouse delivery increased significantly in intervention units but not in control units; there was no difference between the two types of units in uptake of other practices. Pooling rates from all 25 units, use of antibiotics in caesarean section and use of polyglycolic acid sutures increased significantly over the period, but use of steroids in preterm delivery was unchanged. Labour ward guidelines seldom agreed with evidence at baseline; this hardly improved after visits. Educational visits cost pound860 each (at 1995 prices).

CONCLUSIONS

There was considerable uptake of evidence into practice in both control and intervention units between 1994 and 1995. Our educational visits added little to this, despite the informal setting, targeting of senior staff from two disciplines, and donation of educational materials. Further work is needed to define cost effective methods to enhance the uptake of evidence from systematic reviews and to clarify leadership and roles of senior obstetric staff in implementing the evidence.

Detection of fetal messenger ribonucleic acid in maternal blood to determine fetal RhD status as a strategy for noninvasive prenatal diagnosis

OBJECTIVES

Our purpose was to test the hypothesis that reverse transcriptase-polymerase chain reaction for fetal messenger ribonucleic acid in maternal blood is more sensitive than polymerase chain reaction from genomic deoxyribonucleic acid in prenatal determination of fetal RhD blood type.

STUDY DESIGN

Fetal nucleated erythrocytes in peripheral blood from 35 RhD-negative women were enriched by triple-density gradient centrifugation, anti-CD71 magnetic sorted, and deoxyribonucleic acid and ribonucleic acid extracted. Sensitivities of reverse transcriptase-polymerase chain reaction and polymerase chain reaction were compared to predict definitive fetal RhD blood type determined in fetal tissues.

RESULTS

Reverse transcriptase-polymerase chain reaction was significantly more accurate (P = .03) than genomic-polymerase chain reaction in predicting fetal RhD blood type, both overall (28 of 35 vs 22 of 35) and when the fetus was RhD-positive (12 of 19 vs 6 of 19).

CONCLUSIONS

Reverse transcriptase-polymerase chain reaction is more sensitive than genomic-polymerase chain reaction in detection of fetal RhD sequences in maternal blood.