Darryl J. Maxwell

Estimation of fetal lung volume using enhanced 3-dimensional ultrasound: a new method and first result

Objective To measure fetal lung volume using a computer based, enhanced, 3‐dimensional ultrasound imaging system.

Third Trimester Intrauterine Fetal Death Caused by Arterial Aneurysm of the Umbilical Cord

Umbilical artery aneurysm (UAA) of the umbilical cord is an extremely rare lesion, with only 8 reported cases in the English-language literature; 7 of these were associated with significant fetal morbidity or mortality and 4 were associated with fetal trisomy 18. We report an additional case of UAA with normal karyotype that resulted in intrauterine growth restriction and fetal demise. It has been suggested that these aneurysms cause fetal hypoxia and intrauterine fetal death, either by compression of the umbilical vein or by acute kinking of the umbilical cord. Cytogenetic analysis should be performed in all cases diagnosed with this unusual lesion, and placental mosaicism for trisomy 18 should be excluded.

Short communication: Vaginal delivery can be considered in monochorionic diamniotic twins

The outcomes of 60 sets of monochorionic diamniotic (MCDA) twins were compared with 218 sets of dichorionic diamniotic (DCDA) twins. The caesarean section rates for MCDA were similar to those for DCDA twins (56.6 versus 53.6%, P > 0.1). Although the number of babies with 5‐minute Apgar score of <7 was significantly higher for vaginally delivered MCDA twins compared with that of DCDA twins (12 versus 3.5%, P < 0.001), the umbilical artery pH of <7.2 was similar (20 versus 13%, P > 0.05). Admission to neonatal intensive care unit (NICU) and neonatal mortality were also similar in both groups. Delivery by caesarean section was associated with increased admission to the NICU and neonatal mortality for MCDA twins when compared with vaginal delivery group. From this retrospective cohort study, we can conclude that vaginal delivery for MCDA twins appeared to be a reasonable management option when similar selection criteria for vaginal delivery of DCDA twins were applied.

Screening for trisomy 21: the significance of a positive second trimester serum screen in women screen negative after a nuchal translucency scan.

Screening of pregnancies for trisomy 21 is now an accepted part of antenatal care. Measurement of fetal nuchal translucency in the first trimester and analysis of maternal serum biochemistry in the second trimester are both established methods of screening. The performance characteristics of both tests in an unselected population are well described and the choice of test offered is usually determined by local policy and resources. We present data from a screening programme offering women with a low risk result from nuchal translucency measurement a second trimester serum screen. There were eight cases of trisomy 21 in the 2683 women screened, all of which presented with a high-risk nuchal screen result. Serum screening of 1057 women who screened negative by nuchal translucency gave 46 high-risk results, all of which were, therefore, false positive for trisomy 21. Second trimester biochemistry screening following a negative nuchal translucency screen did not increase the detection of trisomy 21.Screening of pregnancies for trisomy 21 is now an accepted part of antenatal care. Measurement of fetal nuchal translucency in the first trimester and analysis of maternal serum biochemistry in the second trimester are both established methods of screening. The performance characteristics of both tests in an unselected population are well described and the choice of test offered is usually determined by local policy and resources. We present data from a screening programme offering women with a low risk result from nuchal translucency measurement a second trimester serum screen. There were eight cases of trisomy 21 in the 2683 women screened, all of which presented with a high-risk nuchal screen result. Serum screening of 1057 women who screened negative by nuchal translucency gave 46 high-risk results, all of which were, therefore, false positive for trisomy 21. Second trimester biochemistry screening following a negative nuchal translucency screen did not increase the detection of trisomy 21.

In vitro estimation of foetal liver volume using ultrasound, x-ray computed tomography and magnetic resonance imaging

Sixteen formalin-fixed foetal livers were scanned in vitro using a new system for estimating volume from a sequence of multiplanar 2D ultrasound images. Three different scan techniques were used (radial, parallel and slanted) and four volume estimation algorithms (ellipsoid, planimetry, tetrahedral and ray tracing). Actual liver volumes were measured by water displacement. Twelve of the sixteen livers also received x-ray computed tomography (CT) and magnetic resonance (MR) scans and the volumes were calculated using voxel counting and planimetry. The percentage accuracy (mean +/- SD) was 5.3 +/- 4.7%, -3.1 +/- 9.6% and -0.03 +/- 9.7% for ultrasound (radial scans, ray volumes), MR and CT (voxel counting) respectively. The new system may be useful for accurately estimating foetal liver volume in utero.

Antenatal detection of arteriovenous anastomoses in monochorionic twin pregnancy

To revalidate the detection technique for arteriovenous anastomoses in an unselected group of monochorionic twins, and to make recommendations about its applicability for more widespread use.

Incorporating 3D and 4D Ultrasound into Clinical Practice

3D ultrasound has been slow to make significant impact in clinical practice. In a large part, this is because 2D ultrasound is of such superior quality that sonographers have not seen any gain in adopting the new technology. More recently, however, diverse application of 3D technology has taken place in many branches of medicine, with obstetrics and gynaecology at the forefront. Several manufacturers now produce machines of remarkable sophistication and utility. Hardware and software have been integrated to allow the release of information from the ultrasound examination that has hitherto not been possible. In addition, virtual real time 3D images (4D ultrasound) have captured the imagination of both public and media. We report our preliminary clinical experience with 3 and 4D ultrasound in a limited clinical environment. While not suitable for wide scale application at present, we believe this technology has inherent advantages that will secure its clinical role and that this role will widen rapidly in the near future.

P06.04: Antenatal detection of arterio-venous (A-V) anastomoses in monochorionic twins—can we incorporate it in routine twin surveillance?

There are only a very few reports of fetal parvovirus infection in the circumstance of a twin pregnancy. We report a case of differential fetal infection following maternal parvovirus infection in a dichorionic twin pregnancy. A 32-year-old woman was diagnosed with parvovirus infection following exposure to her infected child at 19 weeks’ gestation in a dichorionic diamniotic twin gestation. Maternal seroconversion was documented and parvovirus B19 DNA was present on PCR testing. Fetal monitoring with serial ultrasound assessment was instituted and at 25 weeks gestation Twin I (male) displayed mild ascites, pericardial effusion, placentomegaly and oligohydramnios. The MCA PSV was elevated. Twin II (female) was sonographically unremarkable and the MCA PSV was not elevated. A single fetal intravascular transfusion for Twin I was performed (pretransfusion Hb 80 g/L). Twin I fetal blood was positive for parvovirus B19 DNA and serum demonstrated both IgG and IgM. Following the fetal transfusion the sonographic hydrops resolved, although the placentomegaly persisted. Delivery at 37 weeks’ gestation resulted in live male and female fetuses. Both were vigorous at delivery. Individual neonatal venepuncture showed B19 DNA on PCR to be present in Twin I but absent in Twin II. IgM was present for B19 in Twin I but not Twin II. Both neonates had B19 IgG antibodies, passively acquired from the mother. Histopathology of the placentae demonstrated mild edema in that of Twin I but no inclusion cells. The placenta of Twin II was unremarkable. In conclusion, we present a case of discordant fetal infection in a dizygotic dichorionic twin pregnancy for parvovirus, with a dual live birth at term and no adverse perinatal sequelae. This case demonstrates the ability for differential transplacental infection of this virus and the assistance of MCA flow studies to guide therapy in a multiple pregnancy at risk of parvovirus infection.

Late termination for fetal abnormality: providing essential information for parents

Termination of pregnancy for fetal abnormality in the second half of pregnancy is a distressing experience for parents who are often fearful of the process of termination. Some of this fear may be engendered by a lack of information, and staff caring for couples in this situation may not feel sufficiently sure of the likely course of late termination to answer their questions. There is little existing literature to provide guidance. We studied all late terminations for abnormality occurring in our unit over an 18-month period in order to provide parents and staff with appropriate information.