Crown-rump length in chromosomally abnormal fetuses at 10 to 13 weeks' gestation

Automating the Human Action of First-Trimester Biometry Measurement from Real-World Freehand Ultrasound

OBJECTIVE

Automated medical image analysis solutions should closely mimic complete human actions to be useful in clinical practice. However, more often an automated image analysis solution represents only part of a human task, which restricts its practical utility. In the case of ultrasound-based fetal biometry, an automated solution should ideally recognize key fetal structures in freehand video guidance, select a standard plane from a video stream and perform biometry. A complete automated solution should automate all three subactions.

METHODS

In this article, we consider how to automate the complete human action of first-trimester biometry measurement from real-world freehand ultrasound. In the proposed hybrid convolutional neural network (CNN) architecture design, a classification regression-based guidance model detects and tracks fetal anatomical structures (using visual cues) in the ultrasound video. Several high-quality standard planes that contain the mid-sagittal view of the fetus are sampled at multiple time stamps (using a custom-designed confident-frame detector) based on the estimated probability values associated with predicted anatomical structures that define the biometry plane. Automated semantic segmentation is performed on the selected frames to extract fetal anatomical landmarks. A crown-rump length (CRL) estimate is calculated as the mean CRL from these multiple frames.

RESULTS

Our fully automated method has a high correlation with clinical expert CRL measurement (Pearson's p = 0.92, R-squared [R2] = 0.84) and a low mean absolute error of 0.834 (weeks) for fetal age estimation on a test data set of 42 videos.

CONCLUSION

A novel algorithm for standard plane detection employs a quality detection mechanism defined by clinical standards, ensuring precise biometric measurements.

Repeated Measurement of Crown-Rump Length at 9 and 11-13 Weeks' Gestation: Association with Adverse Pregnancy Outcome

Aims: To clarify whether ultrasonographic measurements of crown-rump length (CRL) at 11-13 weeks - based on the number of gestational days determined using the CRL at 9 weeks - can predict fetal prognosis. Methods: A prospective cohort study was conducted to evaluate the association between fetal growth in the first trimester and fetal prognosis. Fetal growth in the first trimester was evaluated measuring CRLs at 11-13 weeks determined using the CRL at 9 weeks. The subjects were divided into short CRL (s-CRL) and normal CRL (n-CRL). The prognoses were compared between the two groups. Results: A total of 126 patients in the s-CRL group and 1,130 patients in the n-CRL group were enrolled. Abortion occurred in 7.1% of s-CRL and 0.9% of n-CRL subjects (p < 0.001). Among the patients with chromosomal abnormalities, the incidence of trisomy 18 was significantly greater in s-CRL (4.8 vs. 0.1%, p < 0.001). Without abortion, placental weight, frequency of small for gestational age (SGA) and birth weight in s-CRL were significantly higher than those in the n-CRL group (12.8 vs. 3.6%, p < 0.001). Conclusions: Measuring CRL at 9 weeks is useful for determining gestational days prior to measuring CRL at 11-13 weeks. After reconfirming the gestational age at 9 weeks, measuring CRL at 11-13 weeks is useful for predicting the incidence of trisomy 18 as well as SGA later in pregnancy.

Can a smaller than expected crown-rump length reliably predict the occurrence of subsequent miscarriage in a viable first trimester pregnancy?

AIM

To elicit the diagnostic value of smaller than expected crown-rump length (CRL) to predict the occurrence of subsequent miscarriage in women with a viable first trimester pregnancy.

METHODS

A cohort study was conducted in the fetal special care unit of a tertiary care maternity hospital. The recruited participants were young pregnant women at 6-13 weeks of gestation. Transvaginal ultrasonography was performed to determine pregnancy viability and measure the embryonic CRL. To compare the differences in CRL between those pregnancies that remained viable and those that subsequently miscarried, the deviation of observed and expected CRL was calculated and expressed in standard deviations (SD) as Z score. The primary outcome measure was the percentage of pregnancies with antecedent growth delay that miscarried by the end of the first trimester.

RESULTS

Of the pregnancies that subsequently miscarried, 79.3% (42/53) had smaller than expected CRL, and in 56.6% (30/53) the CRL was 2 SD or less from that expected for gestational age (GA). The mean Z score for CRL was significantly lower in pregnancies that subsequently miscarried compared to pregnancies that remained viable (-2.9 ± 2.6 vs -0.8 ± 2.1, respectively, P < 0.001). A CRL of 2 SD or less from that expected for GA as a cut-off point had a sensitivity of 56.6, specificity of 81.9, positive predictive value of 36.6, negative predictive value of 91.1, likelihood ratio positive of 3.1 and likelihood ratio negative of 0.5 in predicting subsequent miscarriage.

CONCLUSION

Viable first trimester pregnancies with small for GA CRL were associated with a higher probability of a subsequent miscarriage.

Maternal serum IGF-I, IGFBP-1 and IGFBP-3 at 11-13 weeks in trisomy 21 and trisomy 18 pregnancies

OBJECTIVE

To investigate the possible value of maternal serum concentration of insulin-like growth factor-I (IGF-I), IGF binding protein-1 (IGFBP-1) and IGFBP-3 in first-trimester screening for fetal aneuploidies.

STUDY DESIGN

Maternal serum concentrations of IGF-I, IGFBP-1 and IGFBP-3 at 11-13 weeks of gestation were measured and compared in 30 trisomy 21, 30 trisomy 18 and 120 euploid pregnancies.

RESULTS

The median multiple of the normal median (MoM) values of maternal serum IGF-I, IGFBP-1 and IGFBP-3 in trisomy 21, trisomy 18 and euploid pregnancies were not significantly different (IGF-I: 1.10, 1.14 and 1.0 MoM, respectively; IGFBP-1: 1.10, 1.01 and 1.0 MoM; IGFBP-3: 0.90, 1.16 and 0.98 MoM).

CONCLUSION

Measurement of maternal serum IGF-I, IGFBP-1 and IGFBP-3 at 11-13 weeks of gestation is unlikely to be useful in screening for trisomies 21 and 18.

A model and scoring system to predict outcome of intrauterine pregnancies of uncertain viability

OBJECTIVES

To define the incidence and outcome of intrauterine pregnancy of uncertain viability (PUV) and to develop and assess the performance of a model and a scoring system to predict ongoing viability.

METHODS

Of 1881 consecutive women undergoing transvaginal ultrasonography, a cohort of 493 women with an empty gestational sac < 20 mm in mean diameter, gestational sac < 25 mm in mean diameter and containing yolk sac only or an embryonic pole < 6 mm in maximum length and without visible heart activity were followed until the end of the first trimester. Women with multiple pregnancies or who underwent termination of pregnancy were excluded. Outcome measures were pregnancy viability at initial 7-14-day follow-up and first-trimester viability at 11-14 weeks. The data were split randomly into two sets (two-thirds and one-third, respectively) in order to first develop and then test a mathematical model and a 'simple' model in the prediction of viability at each outcome point, based on maternal demographics, ultrasound features and symptoms. The performance of each system was assessed by receiver-operating characteristics (ROC) curve analysis and calibration plots on a test dataset.

RESULTS

The incidence of PUV in this population was 29.2% (549/1881). Of the 493 pregnancies with initial (7-14 days) follow-up available, 307 (62.3%) were viable at this time and of the 444 pregnancies with follow-up at the end of the first trimester, 225 (50.7%) were still viable. Initial (7-14-day) viability was predicted by the model with an area under the ROC curve (AUC) of 0.837 (95% CI, 0.791-0.884) in the training dataset and 0.821 (95% CI, 0.756-0.885) in the test dataset. First-trimester (11-14-week) viability was predicted by the model with an AUC of 0.788 (95% CI, 0.734-0.842) in the training dataset and 0.774 (95% CI, 0.701-0.848) in the test dataset. The scoring system performed slightly worse than did the model, but had the advantage of being easily applicable.

CONCLUSIONS

When early pregnancy viability cannot be established immediately with ultrasound, use of either a logistic regression model or a scoring system allows an individualized prediction of first-trimester outcome.

Prenatal sonographic features of fetuses in trisomy 13 pregnancies. IV

Prenatal ultrasound is a powerful tool to detect structural abnormalities associated with the fetuses in trisomy 13 pregnancies. This article provides a comprehensive review of the prenatal sonographic markers of trisomy 13 in the first trimester, including fetal nuchal translucency thickness, fetal heart rate, fetal nasal bone, fetal tricuspid regurgitation, ductus venous flow, fetal crown-rump length, fetal trunk and head volume, fetal frontomaxillary facial angle, gestational sac volume and umbilical cord diameter, along with biochemical markers such as maternal serum free beta-human chorionic gonadotropin, maternal serum pregnancy-associated plasma protein-A, maternal serum placental growth factor, and the fetal and total cell-free DNA concentration in the maternal circulation.

Down syndrome screening: imagining the screening test of the future

Prenatal screening for Down syndrome (DS) is performed by risk calculation based on biochemical and biometric parameters. This way, approximately 75-85% of all DS cases can be detected. A way to improve detection rates is to search for new screening markers. Since the majority of biomarkers used in current DS screening are predominantly produced by the placenta, and the presence of an extra chromosome (as in DS) complicates placental development and function, it is plausible to assume that new potential screening markers may also originate from the placenta. Any alterations in these markers can be attributed to abnormal placental development and function. This article focuses on normal early placental development and function compared with that in DS pregnancies. Using this knowledge, we reason towards candidate biomarkers that may be useful in screening for DS.

Placental protein 13 as a first trimester screening marker for aneuploidy

OBJECTIVE

To determine whether Placental Protein 13 (PP13) could be an additional marker in first trimester screening for aneuploidies.

METHODS

To evaluate differences in multiples of the gestation-specific normal median (MoMs), PP13 concentrations were measured in serum samples from Down syndrome, trisomy 18 and 13 affected pregnancies and euploid singleton pregnancies (four for each case matched for duration of storage, maternal weight and age).

RESULTS

The PP13 MoM in Down syndrome cases (n = 153) was 0.91 [not statistically significant from controls (n = 853); P = 0.06; Wilcoxon rank sum test, two-tail]. PP13 MoMs were decreased in trisomy 18 (n = 38-median MoM 0.64; P < 0.0001) and trisomy 13 cases (n = 23-median MoM 0.46; P < 0.0001). There was a slight upward trend in MoM values of the Down syndrome cases with gestational weeks. The PP13 MoM was significantly correlated with the pregnancy associated plasma protein-A MoM and the free beta-subunit of human chorion gonadotrophin (fbeta-hCG) MoM.

CONCLUSION

PP13 does not seem to be a good marker for Down syndrome. PP13 MoMs are, however, significantly lower in trisomy 18 and 13 pregnancies. The addition of PP13 to the current screening test could be valuable for improving the discrimination of aneuploid from euploid pregnancies.

Morphological and functional evaluation of normal and abnormal fetal growth by ultrasonography

Correction or estimation of gestational age is essential for the evaluation of fetal growth. When necessary, an appropriate fetal biometric parameter should be selected depending on fetal size. In the first trimester, crown-rump length (CRL) is appropriate, especially when the CRL is 20-40 mm. In the second trimester, biparietal diameter (BPD), head circumference (HC), and femur length (FL) are of equal predictability. Fetal weight estimation is still the basis of evaluation of fetal growth. The most predictable formula currently available includes the parameters BPD (or HC), abdominal circumference (AC), and FL. Serial measurements of AC are useful for diagnosis of intrauterine growth restriction (IUGR) and macrosomia. Quantitative evaluation of soft tissue deposition may be informative for macrosomia. Functional evaluation using Doppler velocimetry is essential in IUGR cases associated with uteroplacental insufficiency. Analysis of blood velocity waveforms of the umbilical and intracranial arteries, predominantly the middle cerebral artery, is widely performed. An increase in the pulsatility index (PI) or resistance index (RI) of the umbilical artery and/or a decrease in the PI or RI of the middle cerebral artery are highly predictable for fetal hypoxia and/or acidosis.

Dating and growth in the first trimester

Measurement of embryonic or foetal size using the greatest length of the embryo or foetal crown rump length can be used to accurately determine the gestational age of a normal first trimester pregnancy to within three to five days. Transvaginal ultrasound scan can be used to measure the size of an embryo and gestation sac earlier than transabdominal ultrasound. The original Robinson curve used for dating pregnancies is still valid in most cases. Ultrasound dating in the first trimester is now recommended for all women with spontaneous pregnancies, even those with certain menstrual dates. First trimester growth in normal pregnancy is not uniform and is influenced by both maternal and foetal factors. Early foetal growth restriction is demonstrated in many pregnancies that subsequently end in first trimester miscarriage and is also demonstrated in fetuses with triploidy, trisomy 18 and possibly trisomy 13. Pregnancies which are small at the 11-14 week ultrasound scan appear to be at risk of later intrauterine growth restriction, preeclampsia and preterm delivery. Cross-sectional and serial measurement of foetal growth in the first trimester may be helpful in predicting both miscarriage and adverse late pregnancy outcomes.

Evidence of early first-trimester growth restriction in pregnancies that subsequently end in miscarriage

OBJECTIVES

To examine whether viable early pregnancies that subsequently end in miscarriage exhibit evidence of first-trimester growth restriction.

DESIGN

Prospective cohort study.

SETTING

Early pregnancy unit (EPU) of a teaching hospital.

POPULATION

Women attending EPU between 5 and 10 weeks of gestation.

METHODS

Women with spontaneously conceived intrauterine, viable singleton pregnancies with certain last menstrual period and regular cycles were included. The deviation between the observed and expected crown-rump length (CRL) for gestation was calculated and expressed as a z score. Pregnancies were followed up until the 11-14 week scan, and the deviation between those that remained viable and miscarried subsequently was calculated.

MAIN OUTCOME MEASURES

Viability at 11-14 week scan.

RESULTS

Over 6 months, 316 women met the inclusion criteria. Twenty-four (7.4%) women were excluded. Of the remaining 292, the pregnancy remained viable in 251 (86%) and 41 (14%) suffered a miscarriage. At the first transvaginal ultrasound, the z score of the mean measured CRL for pregnancies that remained viable was -0.82, SD 1.46, while in pregnancies that subsequently miscarried the z score was -2.42 and the CRL was significantly smaller, SD 1.31 (P < 0.0001). In the latter group, the initial CRL was below the expected mean for gestational age in all women, while in 61% (25/41), the CRL was at least 2 SDs below the expected mean.

CONCLUSIONS

CRL was significantly smaller in pregnancies that subsequently ended in miscarriage. This suggests that early first-trimester growth restriction is associated with subsequent intrauterine death.

First trimester ultrasonography in screening and detection of fetal anomalies

An obstetrical ultrasound examination provides invaluable information regarding the fetus. Until the mid-1980s, ultrasound in the first trimester was limited to localization of the pregnancy, establishing viability, and accurate dating. With the advent of high-resolution ultrasound and transvaginal scanning, a significant amount of information about the fetus can be gained and provided to the patient at a very early stage in gestation. This article provides an overview of the role of first trimester (11-13 + 6 weeks' gestation) ultrasound in screening and diagnosis of fetal anomalies. The first trimester is an ideal time for screening for aneuploidy, primarily due to the advantages that nuchal translucency (NT) measurement provides. NT measurement is also useful in establishing the risk of congenital cardiac disorders and a number of genetic and non-genetic syndromes. Significant NT thickening is associated with an increase in perinatal morbidity and mortality. Potential mechanisms resulting in increased NT are discussed. A number of new ultrasound markers for fetal aneuploidy have been investigated over the past several years, some of which appear to improve the screening efficacy of early ultrasonography. The role of these is reviewed. A number of fetal anomalies can now be consistently diagnosed in the first trimester. Their appearance at this early gestational age is discussed as well. It is clear that, data obtained by first trimester ultrasound are useful in counseling expectant parents and in planning the appropriate follow-up.

Prediction of delivery date by sonography in the first and second trimesters

OBJECTIVE

To compare the dates of delivery predicted by last menstrual period (LMP), crown-rump length (CRL) and biparietal diameter (BPD) with the actual date of delivery in a population of pregnant women divided into those with certain and those with uncertain LMP.

METHODS

Healthy women were enrolled at the first visit during their pregnancy to a general practitioner in Odense, Denmark, and underwent ultrasound examinations in the first and second trimesters. Data from a study of 798 women who gave birth in the period August 2001 to April 2003 are presented, although only the 657 spontaneous deliveries were used for analysis (n = 339 and 318 in the certain and uncertain LMP groups, respectively). Data on pregnancy and delivery were collected from the medical records. Wilcoxon's signed rank test was used to test the hypothesis of no difference in prediction error (predicted - actual date of delivery) between the three methods.

RESULTS

The median prediction errors estimated by sonography in the first and second trimesters and by corrected LMP according to cycle length were 2.32, 0.16, and 3.00 days, respectively, in women with certain LMP, and 1.71, 0.00, and 3.00 days, respectively, in women with uncertain LMP. The median gestational age at delivery estimated by sonography in the first and second trimesters and by corrected LMP according to cycle length was 282, 280, and 283 days, respectively, in both groups.

CONCLUSION

An ultrasound examination in the second trimester (17-22 completed weeks) is the best predictor of the date of delivery at the individual level, followed by an ultrasound examination in the first trimester. Having an uncertain LMP does not affect the sonographic prediction of date of delivery.

Relation Between Increased Fetal Nuchal Translucency Thickness and Chromosomal Defects

OBJECTIVE

To examine the prevalence and distribution of all chromosomal defects in fetuses with increased nuchal translucency thickness.

METHODS

Assessment of risk for trisomy 21 was carried out by a combination of maternal age and fetal nuchal translucency thickness at 11-13 + 6 weeks. A search of the database was made to identify, first, all singleton pregnancies in which fetal karyotyping was carried out and, second, the cases where the fetal nuchal translucency was equal to or above the 95th centile for fetal crown-rump length. The prevalence and distribution of chromosomal defects were determined for each nuchal translucency category: between the 95th centile for crown-rump length and 3.4 mm, 3.5-4.4 mm, 4.5-5.4 mm, 5.5-6.4 mm, 6.5-7.4 mm, 7.5-8.4 mm, 8.5-9.4 mm, 9.5-10.4 mm, 10.5-11.4 mm, and 11.5 mm or more.

RESULTS

The search identified 11,315 pregnancies. The median maternal age was 34.5 (range 15-50) years, and the median fetal crown-rump length was 64 (range 45-84) mm. The fetal karyotype was abnormal in 2,168 (19.2%) pregnancies, and the incidence of chromosomal defects increased with nuchal translucency thickness from approximately 7% for those with nuchal translucency between the 95th centile for crown-rump length and 3.4 mm to 75% for nuchal translucency of 8.5 mm or more. In the majority of fetuses with trisomy 21, the nuchal translucency thickness was less then 4.5 mm, whereas in the majority of fetuses with trisomies 13 or 18 it was 4.5-8.4 mm, and in those with Turner syndrome it was 8.5 mm or more.

CONCLUSION

In fetuses with increased nuchal translucency, approximately one half of the chromosomally abnormal group is affected by defects other than trisomy 21. The distribution of nuchal translucency is different for each type of chromosomal defect.

LEVEL OF EVIDENCE

II-3.

Cardiac Circumference Measurement: Possible Screening Tool in Early Pregnancy for Anomalous Cardiac Development

OBJECTIVE

In this study, cardiac circumference (CC), measured by transvaginal sonography, was analyzed to determine the growth during the early stage of pregnancy and its relationship to abdominal circumference and femur length (FL).

METHODS

Biometric measurements, including CC, were obtained in 1,182 euploid fetuses at 9-16 weeks' gestation. The CC measurements were related to gestational age (GA), abdominal circumference, and FL. The corresponding 95% confidence intervals were calculated.

RESULTS

A linear growth function was observed between CC (mm) and GA (days) (r2 = 0.601; p < 0.0001; y = 0.573 GA - 24.185). Similarly, a good correlation is described with a linear function between CC (mm) and abdominal circumference (mm) (r2 = 0.70; p < 0.0001; y = 0.343 AC + 3.696) and between CC (mm) and FL (mm) (r2 = 0.626; p < 0.0001; y = 1.335 FL + 14.444). The regression analysis that best correlates the dependent variable CC (mm) with the independent variables, GA (days), abdominal circumference (mm), and FL (mm), is: y = 0.137 GA + 0.235 AC + 0.199 FL - 3.303 (r2 = 0.708; p < 0.0001).

CONCLUSION

Our results provide normative data of the growth of the CC in early pregnancy. The good correlation described between CC and abdominal circumference and FL suggests that cardiac measurements in early pregnancy alone, or related to other fetal biometric parameters, could be used as a screening tool to identify fetuses at risk for abnormal heart development.

Fetal head-to-trunk volume ratio in chromosomally abnormal fetuses at 11 + 0 to 13 + 6 weeks of gestation

OBJECTIVE

To determine the pattern of early growth disturbance in chromosomally abnormal fetuses by comparing the volume of the fetal head to that of the trunk.

METHODS

The fetal trunk and head volume was measured using three-dimensional (3D) ultrasound in 145 chromosomally abnormal fetuses at a median gestational age of 12 (range, 11 + 0 to 13 + 6) weeks. The head volume was measured separately and then subtracted from the total head and trunk volume to obtain the volume of the fetal trunk. The head-to-trunk ratios were then calculated and the Mann-Whitney U-test was used to determine the significance of differences from 500 chromosomally normal fetuses.

RESULTS

The fetal head volume for crown-rump length (CRL) was significantly smaller than normal in trisomy 21, trisomy 13 and Turner syndrome (P < 0.001, P < 0.001 and P = 0.001, respectively), whereas no significant differences were found in trisomy 18 and triploidy (P = 0.139 and P = 0.070, respectively). The fetal trunk volume for CRL was significantly smaller in all chromosomal abnormalities (P < 0.001) except Turner syndrome (P = 0.134). The head-to-trunk ratio for CRL was significantly larger in trisomy 18, trisomy 13 and triploidy (P < 0.001), but normal in trisomy 21 (P = 0.221) and Turner syndrome (P = 0.768).

CONCLUSIONS

In trisomy 21 and Turner syndrome, the growth deficit was symmetrical with the head and trunk being equally affected, whereas in triploidy and trisomies 18 and 13 there was asymmetrical growth restriction with the trunk being more severely compromised than the head.

Alveolar capillary dysplasia in an infant with trisomy 21

We present a case of an infant with Down syndrome (trisomy 21) who was affected by alveolar capillary dysplasia and other complications including endocardial cushion defect, hypothyroidism, and intrauterine growth restriction. The patient was the product of a third pregnancy to a 33-year-old woman with no significant risk factors. The child lived for 3 months, during which he developed intractable dyspnea, hypoxemia, and cardiac dysfunction and he eventually died from septicemia and multiorgan failure. In addition to the facial phenotypic features and cardiac anomalies, the autopsy revealed the characteristic microscopic pulmonary findings of alveolar capillary dysplasia with misalignment of pulmonary veins. This appears to be the first reported case of this anomaly associated with trisomy 21. In addition to the many reasons for pulmonary hypertension that occur in children with trisomy 21, alveolar capillary dysplasia may have to be included in the differential diagnosis although it appears to be a rare association.

Fetal trunk and head volume in chromosomally abnormal fetuses at 11+0 to 13+6 weeks of gestation

OBJECTIVE

To examine the pattern of growth in chromosomally abnormal fetuses at 11+0 to 13+6 weeks of gestation and compare the trunk and head volume to crown-rump length (CRL) in defining the growth deficit in such fetuses.

METHODS

The fetal trunk and head volume was measured using three-dimensional (3D) ultrasound in 140 chromosomally abnormal fetuses at 11+0 to 13+6 (median 12) weeks of gestation, and the values were compared to 500 chromosomally normal fetuses. In each chromosomally abnormal fetus, the observed fetal trunk and head volume was subtracted from the expected mean (delta value) of the chromosomally normal fetuses of the same gestational age, and this difference was expressed as a percentage of the appropriate normal mean. The Mann-Whitney U-test was used to determine the significance of differences between the chromosomally normal and abnormal groups.

RESULTS

In trisomy 21 (n=72) and Turner syndrome (n=14) fetuses, compared to chromosomally normal fetuses, the CRL for gestation was similar (P=0.335 and P=0.317, respectively), but the fetal trunk and head volume was about 10-15% lower (P<0.001 and P=0.004, respectively). In trisomy 18 (n=29), trisomy 13 (n=14) and triploidy (n=11), the deficit in volume was about 45% (P<0.001), whereas the deficit in CRL was less than 15% (P<0.001).

CONCLUSIONS

In the quantification of the degree of early growth impairment in chromosomally abnormal fetuses, measurement of the fetal trunk and head volume using 3D ultrasound may be better than measurement of CRL.

Fetal trunk and head volume measured by three-dimensional ultrasound at 11 + 0 to 13 + 6 weeks of gestation in chromosomally normal pregnancies

OBJECTIVE

To establish the relationship between fetal trunk and head volume measured by three-dimensional (3D) ultrasound and gestational age at 11 + 0 to 13 + 6 weeks of gestation.

METHODS

The fetal trunk and head volume were measured using 3D ultrasound in 417 chromosomally normal fetuses from singleton pregnancies at 11 + 0 to 13 + 6 (median, 12 + 0) weeks of gestation. Regression analysis was used to determine the significance of the association between fetal volume and gestational age. The Bland-Altman analysis was used to compare the measurement agreement and bias for a single examiner and between different examiners.

RESULTS

The fetal trunk and head volume increased linearly with gestation from a mean of 5.8 mL at 11 + 0 weeks to 33.3 mL at 13 + 6 weeks and 1 SD was 4.4 mL. There was also a significant linear association between fetal volume and crown-rump length (CRL), from a mean of 5.1 mL at a CRL of 45 mm to 37.5 mL at a CRL of 84 mm and 1 SD was 2.7 mL. However, within this gestational range, a doubling in CRL, from a mean of 48 mm at 11 + 0 weeks to 79 mm at 13 + 6 weeks, was associated with a 5-6-fold increase in fetal volume. The mean difference in fetal volume between paired measurements by the same sonographer was -0.87 mL (95% limits of agreement, -2.31 to 4.05 mL) and the mean difference between paired measurements by two sonographers was -1.09 mL (-5.49 to 3.32 mL).

CONCLUSIONS

3D ultrasound can provide a reproducible measurement of the fetal trunk and head volume in early pregnancy. At between 11 + 0 and 13 + 6 weeks there is a 5-6-fold increase in fetal volume but only a doubling in CRL.

Fetal gender and sonographic assessment of crown-rump length: implications for multifetal pregnancy reduction

OBJECTIVES

Fetal size is a common criterion for the selection of an individual fetus to be reduced during multifetal pregnancy reduction. We investigated whether a difference in crown-rump length (CRL) exists between male and female fetuses at 9-13 weeks' gestation.

METHODS

A total of 883 singleton pregnancies was evaluated at the time of chorionic villus sampling. The mean gestational age at the time of intervention was 10.9 weeks. Pregnancies were dated by certain last menstrual period (LMP). Pregnancies with uncertain dating by LMP or with a sonographic difference of gestational age > 1 week compared with LMP were excluded, as were all cases with chromosomal abnormalities. CRL differences between male and female fetuses were compared using Student's t-test.

RESULTS

A total of 417 female and 466 male fetuses fulfilled our study criteria. Their gestational ages ranged between 9.3 and 13.9 weeks. We found no significant difference in size between the male and female fetuses.

CONCLUSION

Using the CRL to guide multifetal pregnancy reduction should not result in a clinically significant selection of either gender.

Early transvaginal fetal orbital measurements: a screening tool for aneuploidy?

OBJECTIVE

To assess whether simple biometric parameters such as orbital diameters measured in early pregnancy by transvaginal sonography can be used as screening tools for aneuploid fetuses.

METHODS

The study group consisted of 2771 fetuses of pregnant women referred to our center for genetic amniocentesis and examined by transvaginal sonography between 11 and 16 weeks' gestation. Karyotypes were normal in 2717 fetuses, and 54 fetuses were aneuploid. Individual values for the aneuploid fetuses were compared with normative data obtained previously for single orbital measurements (interocular and binocular distance) versus gestational age and head measurements.

RESULTS

The orbital diameters were within the normal range in the cases with trisomy 21, gonosomal aberrations, trisomy 18, and unbalanced anomalies. Three of the 4 fetuses with trisomy 13 had hypotelorism, confirmed later at autopsy in 2 cases and after delivery in 1 case.

CONCLUSIONS

With regard to the small number of cases, our data suggest that ocular biometric parameters may be useful sonographic markers for trisomy 13, even if further evaluation is needed.

Prenatal diagnosis of hypoplastic left heart syndrome and trisomy 18 in a fetus with normal nuchal translucency and abnormal ductus venosus blood flow at 13 weeks of gestation

We describe a case of early prenatal diagnosis of a major congenital heart anomaly and trisomy 18 in a low-risk pregnant woman. Nuchal translucency (NT) measurement at 13 weeks' gestation was 1.2 mm and Doppler evaluation of the ductus venosus detected a persistent reversed flow during atrial contraction. This finding prompted us to perform fetal echocardiography which showed hypoplastic left heart syndrome. Karyotyping following chorionic villus sampling diagnosed trisomy 18. Review of the recent literature suggests that the finding of an abnormal ductus venosus Doppler pattern in the late first trimester of pregnancy may be an early sign of either congenital cardiac or chromosomal abnormality, even in the presence of normal NT screening.

Uterine artery Doppler at 11-14 weeks of gestation in chromosomally abnormal fetuses

OBJECTIVE

To determine whether the major chromosomal abnormalities are associated with impaired placentation in the first trimester of pregnancy.

METHODS

This was a prospective study of 692 singleton pregnancies undergoing fetal karyotyping at 11-14 weeks of gestation. Uterine artery Doppler was carried out and the mean pulsatility index was calculated just before chorionic villus sampling.

RESULTS

The fetal karyotype was normal in 613 pregnancies and abnormal in 79, including 39 cases of trisomy 21, 11 of trisomy 18, 11 of trisomy 13, eight of Turner syndrome and 10 with other defects. There were no significant differences in the median value of uterine artery mean PI between any of the individual groups. Although in the combined group of trisomy 18, trisomy 13 and Turner syndrome fetuses, the median pulsatility index (1.60) was significantly higher than in the chromosomally normal group (median pulsatility index, 1.51; P = 0.021), in the majority of abnormal fetuses (24 of 30) mean pulsatility index was below the 95th centile of the normal group (mean pulsatility index, 2.34). There was no significant association between uterine artery mean pulsatility index and fetal nuchal translucency thickness or fetal growth deficit.

CONCLUSIONS

The high intrauterine lethality and fetal growth restriction associated with the major chromosomal abnormalities are unlikely to be the consequence of impaired placentation in the first trimester of pregnancy.

Growth hormone binding protein in normal and aneuploid pregnancy: a paradoxical decrease in trisomy 18

OBJECTIVE

To explore whether abnormalities in growth hormone binding protein (GHBP) may underlie the growth restriction associated with fetal aneuploidy.

DESIGN

A retrospective casecontrol study.

SETTING

Monash Medical Centre. Clayton, Victoria, Australia.

POPULATION

Twenty-one trisomy 18, and 30 trisomy 21 pregnancies, and 170 chromosomally normal pregnancies at 15-18 weeks of gestation representing three to five controls per case matched for source, gestation and duration of storage.

METHODS

GHBP was measured using a ligand immunofunctional assay

RESULTS

In the chromosomally normal pregnancies GHBP levels decreased slightly but significantly across the narrow gestational window studied. Compared with controls, levels of GHBP, expressed as median (95% CI) multiples of the median (MoM). in the trisomy 21 pregnancies were similar, 1.0 (0.92-1.39) MoM and 1.27 (1.04-1.50) MoM, respectively; P = 0.061 (Mann-Whitney U test) but were significantly reduced in the trisomy 18 pregnancies, 0.68 (0.5 1-0.84) MoM: P = 0.0014 (Mann-Whitney U test).

CONCLUSIONS

These data suggest that decreased levels of maternal growth hormone binding protein, and by implication growth hormone receptor complement, may underlie the early severe growth restriction that is characteristic of trisomy 18.

Fetal heart rate in chromosomally abnormal fetuses

OBJECTIVES

To determine the effects of chromosomal defects on fetal heart rate at 10-14 weeks of gestation.

METHODS

Fetal heart rate at 10-14 weeks of gestation in 1061 chromosomally abnormal fetuses was compared to that from 25,000 normal pregnancies. The chromosomally abnormal group included 554 cases of trisomy 21, 219 cases of trisomy 18, 95 of trisomy 13, 50 of triploidy, 115 of Turner syndrome and 28 of sex chromosome abnormalities other than Turner syndrome.

RESULTS

In the normal group, fetal heart rate decreased from a mean value of 170 beats per minute (bpm) at 35 mm of crown-rump length to 155 bpm at 84 mm crown-rump length. In trisomy 21, trisomy 13 and Turner syndrome fetal heart rate was significantly higher, in trisomy 18 and triploidy the heart rate was lower and in other sex chromosome defects it was not significantly different from normal. Fetal heart rate was above the 95th centile of the normal range in 10%, 67% and 52% of fetuses with trisomy 21, trisomy 13 and Turner syndrome, respectively. The fetal heart rate was below the 5th centile in 30% of fetuses with triploidy and 19% of those with trisomy 18.

CONCLUSIONS

Trisomy 21, trisomy 13 and Turner syndrome are associated with fetal tachycardia, whereas in trisomy 18 and triploidy there is fetal bradycardia. Inclusion of fetal heart rate in a first-trimester screening program for trisomy 21 by a combination of maternal age and fetal nuchal translucency thickness is unlikely to provide useful improvement in sensitivity.

Histomorphological features of chorionic villi at 10-14 weeks of gestation in trisomic and chromosomally normal pregnancies

This study examines histomorphometric features in chorionic villi obtained by chorionic villus sampling (CVS) at 11-14 weeks of gestation from 124 ongoing pregnancies (38 with trisomy 21, 14 with trisomy 18, 11 with trisomy 13 and 61 chromosomally normal controls). In the trisomy 21 group there was an inverse relationship between fetal nuchal translucency thickness (NT) and villus diameter and number of capillaries per villus cross-section. In about half of the cases there was perivillous fibrinoid present, and the amount of this increased with gestation. Compared to the chromosomally normal group, in trisomy 18 the villus diameter was smaller and the number of capillaries per villus cross-section was reduced. In the trisomy 21 group, villi had an increased percentage of two layered trophoblast present and an increased proportion of villus capillaries with nucleated red blood cells present. In all three trisomies, but particularly in trisomies 18 and 13, both the amount of basophilic stippling of the basement membrane and the proportion of cases with stippling was increased. These results provide data on the possible mechanisms of increased fetal NT and on abnormal placental development in fetal trisomies.

Short communication: trophoblast proliferation is increased in chorionic villi from pregnancies with fetal trisomy 18

Pregnancies with fetal trisomy 18 suffer from severe intrauterine growth restriction from the first trimester. This cross-sectional study of chorionic villi obtained from ongoing singleton pregnancies at 10-14 weeks of gestation, semiquantitatively examines chorionic villus stromal and trophoblastic cell proliferation rates in ongoing chromosomally normal and trisomy 18 pregnancies. Chorionic villi were stained using a standard immunohistochemistry protocol with a monoclonal antibody to the Ki-67 antigen and the number of Ki-67 positive trophoblastic and stromal cells per villous cross-section was compared between groups. The number of Ki-67 positive trophoblastic and stromal cells was significantly higher in the group (n=10) with trisomy 18 compared to the chromosomally normal group (n=25;t=2.1, P=0.03 and t=5.3, P<0.001 respectively). Abnormalities in control of cell turnover during development may be important in the pathogenesis of the clinical features of trisomic pregnancies.

Chromosomally abnormal early ongoing pregnancies: correlation of ultrasound and placental histological findings

The pathophysiology of placental microscopic changes in chromosomally abnormal pregnancies remains poorly understood. We have reviewed the relationship between ultrasound findings and villous histological features in a group of 25 ongoing pregnancies presenting with fetal aneuploidy at 11 to 15 weeks of gestation. The chromosomal abnormalities were diagnosed by chorion villous sampling, and the data were compared with those of a group of 25 chromosomally normal pregnancies undergoing surgical termination and matched for gestational age. The aneuploid group included 10 pregnancies with trisomy 21, nine with trisomy 18, three with triploidy, two with monosomy X, and one with trisomy 13. The overall degree of agreement between the two investigators for the histological diagnosis was good (kappa, 0.64), and the sensitivity of histology ranged between 72.0% and 80.0%. Fetal and placental edema was observed on scan in 10 and 7 cases, respectively, of the aneuploid group and was systematically associated with trophoblastic hypoplasia, stromal edema, or cavitation, reduced vascularization, and ramification of the main villous trunks. Fetoplacental hydrops was not observed in the euploid group. These findings indicate that histological changes observed in the placenta of fetuses from ongoing pregnancies presenting with aneuploidy can be linked with early fetal hydrops. The villous features in these cases are probably secondary to a reduction in the villous circulation due to a cardiovascular defect and leading to generalized stromal edema. The reduced villous branching and trophoblastic hypoplasia could be secondary to the enlargement of all villous types or to a basic defect in placental development.

First trimester ultrasonography of multiple gestations: a review

The objective was to review current literature pertaining to first trimester ultrasonography of multiple gestations. To this goal, all manuscripts published in the English language regarding this topic were selected and reviewed in a MEDLINE search from 1966 through May 1998. Additional sources were identified through cross-referencing. Current widespread application of first trimester ultrasonography and especially transvaginal sonography has introduced a new dimension in both diagnostic and management aspects of multiple gestations. Application of first trimester ultrasonography in multiple gestations enables an earlier and more precise depiction of important anatomical details regarding fetal viability, chorionicity, pregnancy outcome, structural abnormalities, pathophysiology of developmental disorders (such as twin reverse arterial perfusion [TRAP] sequence), early sonographic signs associated with fetal aneuploidy (nuchal translucency and abnormal crown-rump length), and potential fetal growth discordancy. First trimester ultrasonography also assists in guiding operative procedures including: amniocentesis, chorionic villus sampling, and selective fetal reduction. Enhanced information obtained with high-resolution, first trimester transvaginal ultrasonography is rapidly becoming a standard for establishing critical information that will assist clinicians to stratify management of multiple gestations. Given the increasing incidence of multiple gestations because of various assisted reproductive technology modalities, it is important that obstetricians become aware of the potential advantages of first trimester ultrasonography in clinical management of multiple gestations.

Reversed end-diastolic umbilical flow in a first-trimester fetus with congenital heart disease

Reversed end-diastolic umbilical artery velocities and a reduced chorionic sac were first seen at 10 weeks in a pregnancy subsequently showing a normal male karyotype on chorionic villi. Four weeks later Doppler studies demonstrated normal umbilical artery waveforms. At 20 weeks, ultrasound examination of the fetus revealed a mild pericardic effusion, hypoplastic righ heart with hypertrophic myocardium and a single umbilical artery, suggesting pulmonary atresia. After neonatal death, pathological studies confirmed pulmonary atresia. This case suggests that reversed end-diastolic umbilical flow in the first trimester may identify a subgroup of fetuses with a lethal abnormality (heart defect, severe intra-uterine retardation, aneuploidy or others).

Fetal heart rate at 10 to 14 weeks and birthweight

In 6644 singleton pregnancies resulting in live births, the fetal heart rate was measured at 10 to 14 weeks of gestation (median 12). There was no significant association between fetal heart rate and birthweight. These findings demonstrate that if there is an association between fetal heart rate, birthweight and subsequent development of cardiovascular disease the responsible intrauterine insult and/or the adaptive fetal response are not present at 10 to 14 weeks of gestation.

First-trimester growth restriction and fetal aneuploidy: the effect of type of aneuploidy and gestational age

OBJECTIVE

Our purpose was to determine the effect of type of aneuploidy and gestational age on first-trimester fetal growth.

STUDY DESIGN

Crown-rump length measurement was obtained in pregnancies undergoing chorionic villus sampling in three large prenatal diagnosis centers. One hundred forty-four aneuploid fetuses, from 9 to 13 weeks' gestation, were compared with 440 matched control fetuses for evidence of crown-rump length shortening. Shortening was defined by the observed/expected crown-rump length. Expected values of crown-rump length based on last menstrual period were obtained from regression equations generated from a separate normal group. Threshold values for aneuploidy screening were determined on the basis of receiver-operator characteristic curves.

RESULTS

There was significant crown-rump length shortening in trisomy 18 compared with normal fetuses, with observed/expected values < or = 0.80 (odds ratio 13.78, 95% confidence interval 5.64 to 33.88, p < 0.000001); for trisomy 13 the observed/expected crown-rump length was < or = 0.90 (odds ratio 3.64, 95% confidence interval 1.08 to 12.96, p < 0.03). There was no significant shortening of crown-rump length in Down syndrome, with observed/expected values < or = 0.92 (odds ratio 0.86, 95% confidence interval 0.50 to 1.47, p = 0.6). With shortened crown-rump length (observed/expected value < 0.86) the risk of any aneuploidy is increased (odds ratio 2.52, 95% confidence interval 1.6 to 3.96, p < 0.0001). When the first-trimester crown-rump length was shortened by > or = 14 mm, the aneuploidy risk was high (odds ratio 9.04, 95% confidence interval 3.26 to 28.67, p < 0.00001).

CONCLUSION

In the first trimester fetuses with trisomy 18 and 13 appear to be growth restricted, in contrast to fetuses with trisomy 21. In at-risk pregnancies crown-length that is shorter than expected significantly increase the odds that aneuploidy is present.

Umbilical Doppler velocimetry in fetuses with trisomy 18 at 10-18 weeks' gestation

The aim of our study was to obtain measurements of the umbilical artery pulsatility index (PI) in pregnancies before invasive procedures for prenatal diagnosis, in order to investigate its potential prognostic value in predicting trisomy 18. We performed a prospective study including 1785 consecutive women from 10 to 18 weeks with singleton pregnancies undergoing chorionic villus sampling (n = 559) or genetic amniocentesis (n = 1226) in our unit. Doppler measurements were performed transvaginally (tenth to 13th week of gestation) or transabdominally (14th to 18th week of gestation) immediately before the invasive procedure. In 7 out of 10 fetuses subsequently diagnosed as trisomy 18, the PI was above the 95th centile, providing a detection rate of 70 per cent, a specificity of 95.1 per cent, a positive predictive value of 7.7 per cent, and a negative predictive value of 99.8 per cent. When the 90th percentile was assayed as a cut-off, the efficacy of PI as a marker of trisomy 18 yielded a sensitivity of 90 per cent and a specificity of 90.4 per cent, with a positive predictive value of 5.2 per cent and a negative predictive value of 99.9 per cent. We suggest that although the use of a single PI measurement for screening purposes needs to be confirmed by further investigation, trisomy 18 fetuses show an abnormal increase in umbilical PI in the first half of pregnancy, and its relation to the early onset of fetal growth retardation needs to be further explored.

Early prenatal diagnosis of triploidy

OBJECTIVE

Our purpose was to investigate the role of ultrasonography and maternal serum human chorionic gonadotropin in the early prenatal diagnosis of triploid pregnancies.

STUDY DESIGN

A retrospective study on 61,314 consecutive singleton pregnancies examined by ultrasonography at 10 to 14 weeks' gestation was performed to identify the prenatal features of those complicated by triploidy. When available, the serum human chorionic gonadotropin level was measured and ascertained retrospectively. Cases lost to follow-up or for which no karyotype was available were excluded from the final analysis.

RESULTS

Overall there were 18 cases of triploidy identified in a population of 58,862 singleton pregnancies, giving a prevalence of 1 in 3270. Fetal defects were observed in 8 (44.4%) of these cases; these included holoprosencephaly (n = 4), exomphalos (n = 3), and posterior fossa cyst (n = 1). In 6 (33.3%) cases the placenta showed molar changes. The fetal crown-rump length was below the 5th percentile in 10 of the 16 (62.5%) cases for which the menstrual age was also available. Fetal nuchal translucency thickness was above the 95th percentile in 12 (66.7%) cases, and the fetal heart rate was below the 5th percentile in 4 of the 13 (30.8%) cases evaluated. The maternal human chorionic gonadotropin level was high in 11 of the 13 (84.6%) cases tested, with similar distribution of the high values in molar and nonmolar triploidies.

CONCLUSION

The combination of ultrasonographic examination of the fetoplacental features and measurement of the maternal serum level of human chorionic gonadotropin enables the diagnosis of most cases of triploidy at 10 to 14 weeks' gestation.

Noninvasive first-trimester screening for fetal aneuploidy

We reviewed all studies concerning noninvasive first trimester screening for fetal aneuploidy obtained from a MEDLINE search through June 1996 with additional sources identified through cross-referencing. Three screening and diagnostic modalities are of potential application in noninvasive first trimester testing for fetal aneuploidy: ultrasound, maternal biochemical markers, and analysis of fetal cells retrieved from maternal sources. Sensitivities of the sonographic finding of nuchal translucency thickness in combination with maternal age for trisomy 21, performed between 10 and 14 weeks of gestation in experienced hands, and maternal biochemical markers independently may be as high as 86 percent and 60 percent, respectively. Sensitivity, specificity, and predictive values of these diagnostic modalities alone, in combination with each other, or in conjunction with other predisposing factors such as maternal age, in large low risk populations have not currently been established. Analysis of fetal cells retrieved from maternal sources, although more complex, may offer definitive noninvasive prenatal diagnosis yet is not currently available in clinical practice. We conclude that noninvasive first trimester screening for fetal aneuploidy modalities including sonographic examination for nuchal translucency thickness and maternal biochemical markers, is feasible. Clinical feasibility; and all-encompassing clinical management paradigms of these and other early noninvasive first trimester screening methods for fetal aneuploidy, are not yet available.

Combining nuchal translucency with umbilical Doppler velocimetry for detecting fetal trisomies in the first trimester of pregnancy

OBJECTIVE

The aim of our study was to evaluate whether the combined use of umbilical artery pulsatility index (UAPI) and nuchal translucency (NT) measurements would be useful in the prediction of fetal chromosomal abnormalities at 10 to 13 weeks of gestation.

DESIGN

A prospective study.

POPULATION AND METHODS

Five hundred and fifty-three consecutive women with singleton pregnancies between 10 and 13 weeks of gestation, who underwent chorionic villus sampling at our institution. UAPI and fetal NT thickness were measured immediately before the invasive procedure. Pregnancies in which structural malformations had been detected by ultrasound were excluded.

RESULTS

Using the 95th centile and 3 mm as the cutoffs for UAPI and NT, respectively, the detection rate for all chromosomal anomalies was 84.2%, with a false positive rate (1-specificity) of 6.6%, a positive predictive value of 31.3%, and a negative predictive value of 99.4%. Out of the 553 tested pregnancies 502 had both parameters within the normal range and only three of them (0.6%) were chromosomally abnormal; in six of the eight cases (75%) in which both parameters were abnormal a chromosome anomaly was present. Of the 43 cases in which only one parameter was abnormal, 10 were chromosomally abnormal (23.2%).

CONCLUSIONS

Our results suggest that the presence of chromosomal anomalies may be strongly suspected when an increased NT thickness (NT > or = 3 mm) is associated with an abnormally high UAPI at 10 to 13 weeks of gestation. The number of cases studied is small, however, and these conclusions are tentative and preliminary. The value of a single measurement of NT and UAPI for screening purposes needs to be substantiated by further investigation.