Assessment of the cervix in the third trimester of pregnancy using transvaginal ultrasound scanning.

OBJECTIVES: To evaluate the inter- and intra-observer reproducibility of a technique for examining physical characteristics of the uterine cervix in the third trimester of pregnancy using transvaginal ultrasound scanning (TVS). STUDY DESIGN: Forty-six women of over 27-week-gestation underwent TVS of the cervix using a Toshiba 140 scanner with a 6 MHz probe. Twenty were scanned once and 14 women twice by the same operator, and another 12 women by two different operators. Measurements of cervical length, including length and width and opening of the internal os were taken from hardcopy images. Of the 26 women scanned twice, sets of images were analysed by a blinded single observer. Of the 20 women scanned once, measurements from the hardcopy images were taken by two blinded observers. RESULTS: The mean difference in measurement of the distance from the tip of the cervix to foetal head was 2.3mm for two hardcopy image observers,-1.96mm for two scans by the same operator and -1.52 mm for two scanners. Corresponding differences in width of opening of the internal os were 1.8, 0.44 and 0.32 mm, respectively. Interpretation of two images taken on each occasion gave similar results to those taken from three or more images. CONCLUSIONS: This method of obtaining TVS measurements from the cervix from hardcopy images that has satisfactory intra- and inter-observer error. It remains to be established whether this method will be better than Bishop score in predicting the outcome of induced or spontaneous labour. The technique appears to be suited for use in multicentre trials of TVS of the cervix at term.

Ultrasonographic markers for chromosomal abnormalities in women with negative nuchal translucency and second trimester maternal serum biochemistry.

OBJECTIVE: To analyze the value of second trimester ultrasound examination among those women whose fetuses were indicated to be at low risk of chromosomal anomalies on the basis of both first trimester nuchal translucency measurement and second trimester biochemical screening. METHODS: A retrospective study of 5500 pregnancies carried out at the fetal medicine unit, Royal Free Hospital. During a period of over 3 years 5500 pregnancies underwent a first trimester scan and nuchal translucency measurement which enabled the detection of 62% (20 of 32) of all chromosomal anomalies. From the remaining pregnancies that underwent second trimester biochemical screening, 3548 were considered negative (risk < 1:250; using maternal serum free beta human chorionic gonadotrophin and alpha fetoprotein). The ultrasound markers that were examined were: shortened femur length, echogenic bowel, pyelectasis, choroid plexus cysts and echogenic intracardiac foci. The likelihood ratios for chromosomal aneuploides for each of these markers were calculated. RESULTS: Of the 3548 screen negative pregnancies, 3541 (99.8%) had a normal karyotype. Seven (0.2%) fetuses had an abnormal karyotype including four (0.11%) with trisomy 21, one with trisomy 18 and two with 47XXY. Second trimester ultrasound markers were found in two of the five (40%) with severe chromosomal anomalies compared to 184 of 3541 (5.2%) with normal karyotypes. Detection of one or more ultrasound markers in a screen negative pregnancy increased the possibility of chromosomal aneuploidy and a negative ultrasound decreased the risk by a likelihood ratio of 0.6 (95% confidence interval, 0.3-1.3). The risk was considerably increased when two or more markers were detected and we would recommend karyotyping under these circumstances. CONCLUSION: This preliminary data indicates a possible role for abnormal ultrasound markers in assessing the risk of chromosomal abnormalities in patients considered to be at low risk by nuchal translucency and serum screening. However analysis of a much larger study group will have to be conducted to assess the significance of individual markers.

The value of sonography in early pregnancy for the detection of fetal abnormalities in an unselected population.

OBJECTIVE: To determine the value of early pregnancy sonography in detecting fetal abnormalities in an unselected obstetric population. DESIGN Prospective cross-sectional study. All women initially underwent transabdominal sonography and when the anatomical survey was considered to be incomplete, transvaginal sonography was also performed (20.1%). Nuchal translucency was measured and karyotyping was performed as appropriate. SETTING: University Department of Obstetrics and Gynaecology. PARTICIPANTS: 6634 sequential unselected women (mean maternal age 29.9 years, range 13-50; mean gestational age 12+4 weeks, range 11+0-14+6), carrying 6443 live fetuses participated in this study. MAIN OUTCOME MEASURE: Detection rate of fetal anomalies and the associated cost per case detected in early pregnancy. RESULTS: The incidence of anomalous fetuses was 1.4% (92/6443) including 43 chromosomal abnormalities. The detection rate for structural abnormalities was 59.0% (37/63, 95% CI 46.5-72.4) and the specificity was 99.9% in early pregnancy. When the first and second trimester scans were combined, the detection for structural abnormalities was 81.0% (51/63, 95% CI 67.7-89.2). Seventy-eight percent (31/40) of chromosomal abnormalities (excluding three cases of XXY) were diagnosed at 11-14 weeks, either because of a nuchal translucency greater than or equal to the 99th centile for gestational age (43%; 17/40, 95% CI 27.4-60.4), or due to the presence of structural abnormalities (35%; 14/40, 95% CI 21.2-52.8). Sixty-five percent (15/23) of cases of trisomy 21 were also diagnosed either because of having a nuchal translucency greater than or equal to the 99th centile (57.0%; 13/23) or due to the presence of a structural abnormality (9.0%; 2/23). Overall, the detection rate of structurally abnormal fetuses was 59% (37/63) in early pregnancy and 81% in combination with the second trimester scan. The cost per abnormality diagnosed in early pregnancy is estimated to be pound sterling 6258 per structurally abnormal fetus, pound sterling 7470 per chromosomal abnormality and pound sterling 4453 per anomalous fetus. CONCLUSION: The majority of fetal structural and chromosomal abnormalities can be detected by sonographic screening at 11-14 weeks, but the second trimester scan should not be abandoned.

The sonographic identification of fetal gender from 11 to 14 weeks of gestation.

OBJECTIVE: To determine the feasibility of correctly identifying fetal gender from 11 to 14 weeks' gestation. METHODS: A prospective cross-sectional study in a university Department of Obstetrics and Gynaecology, London. A total of 524 women from an unselected population underwent a detailed assessment of fetal anatomy at 11-14 weeks of gestation (confirmed by crown-rump length) by means of transabdominal sonography, and transvaginal sonography (26%) when necessary. Fetal gender was identified in the transverse and sagittal planes, and was confirmed at birth. RESULTS: The overall success of correctly assigning fetal gender increased with gestational age from 46% to 75%, 79% and 90% at 11, 12, 13 and 14 weeks, respectively. The ability of the operator to assign fetal gender significantly improved with increasing gestational age (p < 0.0001), being 59%, 87%, 92% and 98% at 11, 12, 13 and 14 weeks, respectively. The accuracy of correctly identifying fetal gender when attempted did not change with gestational age. Fetal gender or the performance of the scan by different operators did not affect the results. CONCLUSION: Whilst the accuracy of sonographic determination of fetal gender at 11-14 weeks is good, it still falls significantly short of invasive karyotyping tests.

Increased nuchal translucency and CATCH 22.

Recent developments in cytogenetics has shown that 22q11 microdeletion is related to a broad spectrum of malformations which are described under the acronym CATCH 22 (Cardiac, Abnormal faces, Thymic hypoplasia, Cleft palate, Hypocalcaemia and 22 chromosome deletion). We describe a case of a fetus with increased nuchal translucency at 12 weeks' gestation presenting with congenital cardiac defects of DiGeorge syndrome type and hypocalcaemia at birth. The neonate was also diagnosed as carrying the 22q11 microdeletion. When nuchal translucency measurement is increased, CATCH 22 spectrum of malformations should be considered and therefore a thorough karyotype analysis should be performed to exclude microdeletion of chromosome 22.

First trimester sonographic detection of chromosomal abnormalities in an unselected population.

OBJECTIVE: To investigate the role of first trimester sonography in detecting chromosomal abnormalities in an unselected obstetric population. METHODS: 2281 women (mean maternal age 30 years [range 16-47]; mean gestational age 12(+3) weeks [range 11-14]) underwent transabdominal scanning to assess fetal structure and, if anatomical survey was considered to be incomplete (31% of cases), transvaginal sonography was also performed. Measurement of nuchal translucency was included and karyotyping performed as considered appropriate. RESULTS: There were 16 chromosomal abnormalities; 13 (81%) were diagnosed at 11-14 weeks either because of a nuchal translucency greater than or equal to the 99th centile for gestational age (7/16; 44% [95% CI 25-63]) or due to the presence of structural abnormalities (6/16; 38% [95% CI 14.2-61.8]). Seventy-five percent of cases of trisomy 21 were also diagnosed either because of having a nuchal translucency greater than or equal to the 99th centile (5/8; 63%) or due to the presence of a structural abnormality (1/8; 13%). CONCLUSIONS: A significant proportion of fetal chromosomal abnormalities can be detected by first trimester sonographic screening to assess fetal structural appearance. The sensitivity of detection can be improved by combining measurement of nuchal translucency with detailed examination of fetal anatomy.

The significance of choroid plexus cysts, echogenic heart foci and renal pyelectasis in the first trimester.

OBJECTIVE: To determine the significance of certain soft ultrasonographic markers for chromosomal abnormalities in the first trimester. DESIGN: This was a prospective cross-sectional study. SETTING: University Department of Obstetrics and Gynaecology, London, UK. METHODS: A total of 5385 women from an unselected population underwent a detailed assessment of fetal anatomy at 11-14 weeks of gestation (confirmed by crown-rump length) by transabdominal sonography (5.0 MHz) and transvaginal sonography (6.0 MHz) when necessary. RESULTS: In normal fetuses, the prevalences of choroid plexus cysts, pyelectasis and echogenic heart foci were 2.2, 0.9 and 0.6%, respectively in the first trimester and 2.0, 0.8 and 0.8%, respectively in the second trimester. Pyelectasis (likelihood ratio = 8.0, p = 0.03) and echogenic heart foci (likelihood ratio = 10.3, p = 0.02) were found to be associated significantly with fetal aneuploidy, while choroid plexus cysts were not. CONCLUSIONS: Although the majority of aneuploidies were detected by increased nuchal translucency and/or the presence of structural abnormalities (78%; 25/32), the use of soft ultrasonographic markers in the first trimester would have increased the overall detection by a further 3%. These data are preliminary and many thousands of pregnancies will need to be examined to determine the significance of the individual markers in different chromosomal abnormalities.