Cranial sonographic markers of fetal open spina bifida at 11 to 13 weeks of gestation

First-trimester ultrasound of the cerebral lateral ventricles in fetuses with open spina bifida: a retrospective cohort study

BACKGROUND

Beyond 18 weeks of gestation, an increased size of the fetal lateral ventricles is reported in most fetuses with open spina bifida. In the first trimester of pregnancy, the definition of ventriculomegaly is based on the ratio of the size of the choroid plexus to the size of the ventricular space or the entire fetal head. However, contrary to what is observed from the midtrimester of pregnancy, in most fetuses with open spina bifida at 11 to 13 weeks of gestation, the amount of fluid in the ventricular system seems to be reduced rather than increased.

OBJECTIVE

This study aimed to compare the biometry of the lateral ventricles at 11 0/7 to 13 6/7 weeks of gestation between normal fetuses and those with confirmed open spina bifida.

STUDY DESIGN

This was a retrospective cohort study that included all cases of isolated open spina bifida detected at 11 0/7 to 13 6/7 weeks of gestation over a period of 5 years and a group of structurally normal fetuses attending at our center over a period of 1 year for the aneuploidy screening as controls. Transventricular axial views of the fetal brain obtained from cases and controls were extracted from the archive for post hoc measurement of cerebral ventricles. The choroid plexus-to-lateral ventricle length ratio, sum of the choroid plexus-to-lateral ventricle area ratio, choroid plexus area-to-fetal head area ratio, and mean choroid plexus length-to-occipitofrontal diameter ratio were calculated for both groups. The measurements obtained from the 2 groups were compared, and the association between each parameter and open spina bifida was investigated.

RESULTS

A total of 10 fetuses with open spina bifida were compared with 358 controls. Compared with controls, fetuses with open spina bifida showed a significantly smaller size of the cerebral ventricle measurements, as expressed by larger values of choroid plexus-to-lateral ventricle area ratio (0.49 vs 0.72, respectively; P<.001), choroid plexus-to-lateral ventricle length ratio (0.70 vs 0.79, respectively; P<.001), choroid plexus area-to-fetal head area ratio (0.28 vs 0.33, respectively; P=.006), and choroid plexus length-to-occipitofrontal diameter ratio (0.52 vs 0.60, respectively; P<.001). The choroid plexus-to-lateral ventricle area ratio was found to be the most accurate predictor of open spina bifida, with an area under the curve of 0.88, a sensitivity of 90%, and a specificity of 82%.

CONCLUSION

At 11 0/7 to 13 6/7 weeks of gestation, open spina bifida is consistently associated with a reduced amount of fluid in the lateral cerebral ventricles of the fetus, as expressed by a significantly increased choroid plexus-to-lateral ventricle length ratio, choroid plexus-to-lateral ventricle area ratio, choroid plexus area-to-fetal head area ratio, and choroid plexus length-to-occipitofrontal diameter ratio.

Research progress on ultrasound and molecular markers for prenatal diagnosis of neural tube defects

Neural tube defects (NTDs) are severe congenital anomalies that result from the failure of early neural tube closure during fetal neurogenesis. They are the most common and severe congenital malformations of the central nervous system. Identifying reliable prenatal diagnostic ultrasound and molecular markers that can predict NTDs is of paramount importance. Early diagnosis of NTDs allows embryonic treatment and prevention strategies, which are crucial for reducing the disability rate associated with these malformations, reducing the burden on individuals and on society. The purpose of this comprehensive review was to summarize the ultrasound biomarkers between 11 and 13 weeks of gestation and the molecular biomarkers used in the diagnosis of NTDs, providing additional insights into early screening for NTDs.

A novel artificial intelligence model for measuring fetal intracranial markers during the first trimester based on two-dimensional ultrasound image

OBJECTIVE

To establish reference ranges of fetal intracranial markers during the first trimester and develop the first novel artificial intelligence (AI) model to measure key markers automatically.

METHODS

This retrospective study used two-dimensional (2D) ultrasound images from 4233 singleton normal fetuses scanned at 11+0-13+6 weeks of gestation at the Affiliated Suzhou Hospital of Nanjing Medical University from January 2018 to July 2022. We analyzed 10 key markers in three important planes of the fetal head. Based on these, reference ranges of 10 fetal intracranial markers were established and an AI model was developed for automated marker measurement. AI and manual measurements were compared to evaluate differences, correlations, consistency, and time consumption based on mean error, Pearson correlation analysis, intraclass correlation coefficients (ICCs), and average measurement time.

RESULTS

The results of AI and manual methods had strong consistency and correlation (all ICC values >0.75, all r values >0.75, and all P values <0.001). The average absolute error of both only ranged from 0.124 to 0.178 mm. AI achieved a 100% detection rate for abnormal cases. Additionally, the average measurement time of AI was only 0.49 s, which was more than 65 times faster than the manual measurement method.

CONCLUSION

The present study first established the normal standard reference ranges of fetal intracranial markers based on a large Chinese population data set. Furthermore, the proposed AI model demonstrated its capability to measure multiple fetal intracranial markers automatically, serving as a highly effective tool to streamline sonographer tasks and mitigate manual measurement errors, which can be generalized to first-trimester scanning.

Pre and postnatal care characteristics and management features of children born with myelomeningocele in the post-folate fortification era of staple foods in Costa Rica (2004-2022)

PURPOSE

To describe the clinical characteristics of pre- and postnatal care of children born with myelomeningocele in Costa Rica from 2004 to 2022 after the introduction of mandatory fortification of four major staple foods, describing the clinical features of this cohort including the size of the meningomyelocele, neurological level, presence of symptomatic Chiari II at birth, kyphosis, and the severity of hydrocephalus requiring cerebrospinal fluid (CSF) shunting. These results were compared against the pre-fortification historical data to determine favorable outcomes from this health policy.

METHODS

We performed a retrospective review of the clinical records of patients with myelomeningocele at the spina bifida clinic from the National Children's Hospital of Costa Rica who were born between 2004 and 2022, a period when staple food fortification was implemented in the country for four food staples (wheat and corn flour, rice, and dairy products). Pre and postnatal care data pertaining to the number of obstetric ultrasound studies, the trimester in which they were performed, the detection of myelomeningocele and associated hydrocephalus, gestational age and route of delivery, neurological level, myelomeningocele defect size, associated kyphosis and symptomatic Chiari II malformation at birth, time periods of myelomeningocele repair, and CSF shunting were examined. A descriptive comparative frequency analysis between myelomeningocele (MMC) defect size, CSF shunt insertion, symptomatic Chiari II, and kyphosis between the different functional levels was performed with the estimation of the Fisher's exact chi-square test by contingency tables, and 0.05 was set as significance level. Additionally, the postnatal features of this cohort were compared against pre-fortification historical data obtained from 100 live-born patients between 1995 and 1996.

RESULTS

A total of 215 patients that were live born between 2004 and 2022 were eligible for analysis with a follow up ranging from 1 to 19 years (median follow up: 7.9 years). Among 99.1% of the mothers of patients who had prenatal consultations, 95.8% had an average of 3.8 obstetric ultrasound studies which led to a 59% prenatal detection rate of myelomeningocele. The pre and post fortification features showed a male/female ratio that changed from 0.92 to 1.25 respectively. Among these newborns, there was an increase from 54 to 64% cesarean sections as method for delivery. Only 26% of the pre fortification patients had the MMC defect repaired in the first 24 h, 32% from 24 to 72 h, 20% from 72 h to 1 week, and 22% later than 10 days respectively which deeply contrasted with the post fortification cohort where 7.5% had the MMC defect repaired in less than 8 h, 12.2% from 8 to 12 h, 66.5% 12-24 h, and 12.7% from 24 to 48 h and 1% later than 48 h, respectively (P < 0.01). Regarding the post fortification myelomeningocele anatomic and functional characteristics, defect size was measured as less than 3 cm in 7% of cases, 3 to 5 cm in 50% of cases, 5 to 7 cm in 42% of cases, and greater than 7 cm in 1% of cases. Thirteen percent of the cases had paraplegia due to a thoracic level, 10% had a high lumbar level, 58% had a middle lumbar level, 13% a lower lumbar level, and 6% only sacral compromise. When the data from the pre and post fortification cohorts were adjusted and compared, there was a reduction from thoracic/high lumbar cases from 26 to 23% (P < 0.56), with an increase of middle lumbar cases from 43 to 58% and a reduction from 25 to 13% of low lumbar cases (P < 0.01) while there was no change in the 6% percentage of sacral cases respectively. Lesions that were considered too extensive or larger than 7 cm decreased from 7 to 1% while associated kyphotic deformities decreased from 6 to 1.4% (P < 0.01); symptomatic Chiari II malformation at birth also decreased from 7 to 2% in the pre- and post-fortification cohorts respectively with all these changes being statistically significant (P < 0.01). Seventy-nine percent and 80% of the pre and post FAF cohorts required CSF VP shunting with a mean time for insertion of 10 days after spinal defect closure with no significant statistical change between the two groups.

CONCLUSIONS

This study describes a four-staple folate fortified population of live-born patients with myelomeningocele lesions whose neurological level, defect size, and associated deformities such as spinal kyphosis and symptomatic Chiari II at birth suggest that folate fortification could have diminished the severity of this congenital disease.

Basic sonographic examination of the fetal brain at 11-13 weeks' gestation: Rationale for a simple and reliable four-step technique

The widespread incorporation of first-trimester scanning between 11 and 13 weeks' gestation has shifted from the screening of chromosomal abnormalities, mainly by measuring nuchal translucency thickness and visualization of the nasal bone, to a more detailed study of the fetal anatomy leading to early detection of several structural congenital anomalies. This goal can be improved by the routine and focused sonographic assessment of specific anatomic planes and the identification of distinctive landmarks that can help disclosing a particular, non-evident condition. In this article we present the basis for a basic, early examination of the fetal brain during screening using a four-step technique, which can be readily incorporated during the first-trimester scan. The technique includes the focused visualization of the cranial contour, choroid plexuses of the lateral ventricles and midline, aqueduct of Sylvius, brainstem, fourth ventricle, and the choroid plexus of the fourth ventricle. The rationale for this approach is presented and discussed.

Qualitative and quantitative study of fetal posterior fossa during the first trimester in a Chinese population

Background

To establish the normal reference ranges for parameters related to the fetal posterior fossa in the first trimester (11 ~ 13+6 weeks of gestation) and to analyze the relationship between them and crown-rump length (CRL) among the Chinese population.

Methods

Singleton pregnancies of 11 ~ 13⁺⁶ weeks (CRL:45 ~ 84 mm) with both parents from China were randomly selected from January 2021 to November 2021. The related parameters of the posterior fossa including cisterna magna (CM), intracranial translucency (IT), brain stem (BS), brain stem to the occipital bone (BSOB), and brain stem/brain stem to occipital bone (BS/BSOB) were evaluated and measured in nuchal translucency (NT) mid-sagittal section clearly by an experienced sonographer (operator 1). To assess the reproducibility of the measurements, we randomly selected 50 pregnant women. According to the blind method, operators 1 and 2 respectively screened and measured relevant parameters. In addition, operator 1 examined and measured relevant parameters again 2 h after the first.

Results

This study included 1663 fetuses. All fetuses can clearly show the three spaces of the fetal posterior fossa. The ICCs (95% CI) of intra-operator reproducibility of CM, IT, BS, BSOB, BS/BSOB were 0.981 (0.952 ~ 0.991, P < 0.001), 0.929 (0.866 ~ 0.961, P < 0.001), 0.970 (0.946 ~ 0.983, P < 0.001), 0.991 (0.974 ~ 0.996, P < 0.001), 0.939 (0.892 ~ 0.965, P < 0.001), respectively; The ICCs (95% CI) of inter-operator reproducibility 0.926 (0.860 ~ 0.960, P < 0.001), 0.810 (-0.083 ~ 0.940, P < 0.001), 0.820 (0.645 ~ 0.904, P < 0.001), 0.804 (0.656 ~ 0.888, P < 0.001), 0.772 (0.599 ~ 0.871, P < 0.001), respectively. There was a linear correlation between CRL and the parameters related to the posterior fossa (CM, IT, BS, BSOB, BS/BSOB). CM (mm) = -1.698 + 0.532 × CRL (cm) (r = 0.829, P < 0.001); IT (mm) = 0.701 + 0.179 × CRL (cm) (r = 0.548, P < 0.001); BS (mm) = 0.403 + 0.349 × CRL (cm) (r = 0.716, P < 0.001); BSOB (mm) = -0.277 + 0.719 × CRL (cm) (r = 0.829, P < 0.001); BS/BSOB = 0.747—0.021 × CRL (cm) (r = 0.196, P < 0.001).

Conclusions

Qualitative and quantitative assessment of the fetal posterior fossa structure was feasible in the first trimester. We constructed the normal reference ranges of CM, IT, BS, BSOB, and BS/BSOB. Furthermore, CM, IT, BS, and BSOB were positively correlated with CRL, but BS/BSOB was negatively correlated with CRL.

First trimester examination of fetal anatomy: clinical practice guideline by the World Association of Perinatal Medicine (WAPM) and the Perinatal Medicine Foundation (PMF)

This recommendation document follows the mission of the World Association of Perinatal Medicine in collaboration with the Perinatal Medicine Foundation. We aim to bring together groups and individuals throughout the world for precise standardization to implement the ultrasound evaluation of the fetus in the first trimester of pregnancy and improve the early detection of anomalies and the clinical management of the pregnancy. The aim is to present a document that includes statements and recommendations on the standard evaluation of the fetal anatomy in the first trimester, based on quality evidence in the peer-reviewed literature as well as the experience of perinatal experts around the world.

Applicability of a semiautomated volumetric approach (5D CNS+™) for detailed antenatal reconstruction of abnormal fetal CNS anatomy

BACKGROUND

The aim of this study was to evaluate the accuracy and reliability of a semiautomated volumetric approach (5D CNS+™) when examining fetuses with an apparent abnormal anatomy of the central nervous system (CNS).

METHODS

Stored 3D volumes extracted from a cohort of > 1.400 consecutive 2nd and 3rd trimester pregnancies (range 15-36 gestational weeks) were analyzed using the semiautomatic software tool 5D CNS+™, enabling detailed reconstruction of nine diagnostic planes of the fetal brain. All 3D data sets were examined and judged for plane accuracy, the need for manual adjustment, and fetal CNS anomalies affecting successful plane reconstruction.

RESULTS

Based on our data of 91 fetuses with structural cerebral anomalies, we were able to reveal details of a wide range of CNS anomalies with application of the 5D CNS+™ technique. The corresponding anatomical features and consecutive changes of neighboring structures could be clearly demonstrated. Thus, a profound assessment of the entire altered CNS anatomy could be achieved in nearly all cases. The comparison with matched controls showed a significant difference in volume acquisition (p < 0.001) and in need for manual adjustment (p < 0.001) but not in the drop-out rates (p = 0.677) of both groups.

CONCLUSION

5D CNS+™ is applicable in the majority of cases with brain lesions and constitutes a reliable tool even if the integrity of the fetal CNS is compromised by structural anomalies. Using volume data that were acquired in identical cutting sections needed for conventional biometry allows for detailed anatomic surveys grossly independent of the examiner's experience.

Evaluation of sensitivity and accuracy of maternal serum alpha fetoprotein to the diagnosis of open spina bifida in comparison with sonographic findings of open spina bifida and Chiari II malformation in pregnant women

Background

NTD is one of the most important problems of the nervous system and the second fetal anomaly that is associated with high mortality and morbidity. Therefore, its prenatal diagnosis is very important. AFP has a high false positive, which reduces its diagnostic value, so the discovery of ultrasound findings in OSB is very important and can replace AFP testing.

Results

4 patients with positive OSB were detected and their diagnosis was confirmed during pathological follow-up (100% diagnostic accuracy) and the rest of the patients with high AFP (51 patients) were negative for OSB. Therefore, the diagnostic accuracy of AFP during statistical analysis was about 7%, which is a very low value.

Conclusion

According to the results of this study, IT, BS, BSOB, BS/BSOB ultrasound criteria in the first screening and decreased BPD and ventriculomegaly in the second screening ultrasound in OSB diagnosis have a higher diagnostic value than the AFP laboratory level. It should pay more attention to MS-AFP results in OSB screening.

First-Trimester Cranial Ultrasound Markers of Open Spina Bifida

OBJECTIVES

To evaluate cranial ultrasound markers during a first-trimester routine ultrasound examination for screening for open spina bifida (OSB).

METHODS

Midsagittal and axial images of the fetal head obtained from fetuses with spina bifida and unaffected control fetuses at 11 weeks to 13 weeks 6 days were analyzed retrospectively. The observed markers of the posterior brain included the 4- versus 3-line view, the brain stem (BS)-to-brain stem-occipital bone (BSOB) distance ratio (BS/BSOB), the position relationship between the maxillo-occipital (MO) line and the midbrain-BS junction, and the crash sign status.

RESULTS

This study included 9 OSB cases, 2 closed spina bifida (CSB) cases, and 200 unaffected controls. Eight of 9 OSB cases had informative midsagittal views of the head. The 3-line view (abnormal) and BS/BSOB greater than 1 (abnormal) were observed in 87.5% (7 of 8) and 100% (8 of 8), respectively. The midbrain-BS junction was below or nearly on the MO line (abnormal) in 100% (8 of 8). Seven of the cases had informative axial views of the head. The crash sign (abnormal) was observed in 85.7% (6 of 7). A 3-line view was seen in all of the cases that had a positive crash sign. Neither of the 2 cases of CSB and none of the controls had any of the 4 first-trimester intracranial ultrasound markers of OSB.

CONCLUSIONS

The 4 first-trimester intracranial ultrasound markers investigated in this study appear to be very good markers of OSB, especially a BS/BSOB greater than 1 and an abnormal MO line. The crash sign and 3-line view were observed in the same fetus. In our study, these ultrasound findings were not helpful in CSB.

Diagnostic accuracy of fetal choroid plexus length to head biometry ratio at 11 to 13 weeks for open spina bifida

BACKGROUND

Open spina bifida is a major congenital anomaly with an estimated incidence of <1 in 1000. The diagnosis of open spina bifida is usually made during the second trimester, but first-trimester detection rate of spina bifida is increasingly reported. Recently, the mean choroid plexus length to occipitofrontal diameter ratio was reported to be increased in fetuses with open spina bifida. The ratio reflects the so-called dry brain effect caused by cerebrospinal fluid leakage and expansion of the choroid plexus into the lateral ventricles. The mean choroid plexus length to occipitofrontal diameter ratio appears to be a promising tool for early detection of open spina bifida, but its diagnostic accuracy is yet to be determined in a large cohort.

OBJECTIVE

This study aimed to assess the predictive accuracy of mean choroid plexus length to occipitofrontal diameter ratio recorded at 11 to 13 weeks' gestation for the detection of open spina bifida.

STUDY DESIGN

This was a retrospective cohort of patients treated in a tertiary referral center. Fetuses in which open spina bifida was detected at 16 to 24 weeks' gestation and normal fetuses were included in the cohort. Biparietal diameter and occipitofrontal diameter were measured in an axial view. The length of choroid plexus was measured along its longest diameter in the same plane. Ultrasound images were examined offline, and the operator was blinded to the clinical diagnosis. The predictive accuracy was evaluated using the area under the curve and positive and negative predictive values.

RESULTS

We included 3300 pregnant women, of whom 24 (0.73%) had the fetuses affected by open spina bifida. The area under the curve values were 0.921 for mean choroid plexus length to occipitofrontal diameter ratio and 0.933 for its multiple of the median. Mean choroid plexus length to biparietal diameter ratio indicated similar results, with area under the curve values of 0.928 and 0.931 for raw ratio and multiple of the median ratio models, respectively. The optimal cutoffs of the mean choroid plexus to occipitofrontal diameter ratio and multiple of the median ratios were 0.662 and 1.263, respectively. The optimal mean choroid plexus to occipitofrontal diameter ratio and multiple of the median ratio cutoffs provided a positive predictive value of 90.9% and a negative predictive value of 99.6%. The number of affected spinal segments was significantly higher in fetuses with a ratio above 0.662 (P=.022).

CONCLUSION

The mean choroid plexus length to occipitofrontal diameter ratio at 11 to 13 weeks' gestation is a promising tool for the prenatal detection of open spina bifida.

Screening for Open Spina Bifida in a Routine Clinical Setting at the First-Trimester Scan: A Prospective Multicentre Cohort Study

OBJECTIVE

The aim of this study was to investigate the performance of screening for open spina bifida (OSB) integrated into the routine first-trimester screening.

METHOD

This is a prospective multicentre study of 4,755 women undergoing first-trimester ultrasound scans over a 4-year period. Measurements of the brainstem (BS) diameter and brainstem-to-occipital-bone (BSOB) distance were performed. The cisterna magna (CM) was measured in the tilted axial view.

RESULTS

Pregnancy outcome data were available for 4,658 fetuses included in this study. There were 5 fetuses with OSB, and in all of them, the BS/BSOB ratio and the CM measurements were abnormal. The sensitivity and specificity of a BS/BSOB ratio >1 were 100%. The sensitivity of a CM width <5th centile was 100%, and the specificity was 95.1%. In 4.6% of cases, the BS/BSOB ratio was between the 95th percentile and 1. In 87.1% of these cases, the CM was normal, and 12.9% had a CM below the 5th percentile.

CONCLUSION

Screening for OSB is feasible in routine first-trimester scans. The BS/BSOB ratio shows a very good sensitivity and specificity. In cases with near-normal values for the BS/BSOB ratio, the CM width might be helpful for further assessment.

Fetal Open and Closed Spina Bifida on a Routine Scan at 11 Weeks to 13 Weeks 6 Days

OBJECTIVES

This study aimed to determine the sensitivity of a first-trimester routine scan in detecting spina bifida (SB) and evaluating the first-trimester intracranial signs.

METHODS

This retrospective study was a review of a prospectively collected database. All cases of SB diagnosed in a tertiary center from 2008 to 2015 were identified. The ultrasound images and medical records were reviewed. All cases of SB diagnosed prenatally were confirmed at birth or autopsy.

RESULTS

A total of 24 cases of SB were diagnosed from 53,349 pregnancy cases. Except for 10 cases with a body stalk anomaly, craniorachischisis, or iniencephaly, 7 cases with open spina bifida (OSB) and 7 cases with closed spina bifida (CSB) were analyzed. The first-trimester detection rates were 100% (7 of 7) for OSB and 28.5% (2 of 7) for CSB. Eight cases were highly suspected of SB in the first trimester because of an abnormal appearance of the posterior brain; 3 were false-positive cases. Two isolated cases of OSB had first-trimester intracranial signs. An obliterated cisterna magna (CM) showed the highest sensitivity for OSB but low specificity. Two cases of OSB had no discernible landmark of intracranial translucency and the CM, and 4 showed normal intracranial translucency with an obliterated CM. All CSB cases were coupled with a normal hind brain except for 2 cases.

CONCLUSIONS

A first-trimester routine scan has high sensitivity in screening for OSB. The CM may be the most sensitive intracranial sign.

First-trimester fetal neurosonography: technique and diagnostic potential

Most brain abnormalities are present in the first trimester, but only a few are detected so early in gestation. According to current recommendations for first-trimester ultrasound, the fetal head structures that should be visualized are limited to the cranial bones, the midline falx and the choroid-plexus-filled ventricles. Using this basic approach, almost all cases of acrania, alobar holoprosencephaly and cephalocele are detected. However, the majority of other fetal brain abnormalities remain undiagnosed until the midtrimester. Such anomalies would be potentially detectable if the sonographic study were to be extended to include additional anatomic details not currently included in existing guidelines. The aim of this review article is to describe how best to assess the normal fetal brain by first-trimester expert multiplanar neurosonography and to demonstrate the early sonographic findings that characterize some major fetal brain abnormalities. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Accuracy of qualitative and quantitative cranial ultrasonographic markers in first-trimester screening for open spina bifida and other posterior brain defects: a systematic review and meta-analysis

BACKGROUND

The significant number of qualitative and quantitative ultrasound markers described for first-trimester screening of open spina bifida (OSB) and other posterior brain defects (oPBD) has resulted in their complex implementation and interpretation for a widespread screening and in a lack of consensus regarding diagnostic accuracy.

OBJECTIVES

To assess and compare the accuracy of qualitative and quantitative cranial sonographic markers at 11-14 weeks of gestation for the detection of OSB and oPBD.

SEARCH STRATEGY

A systematic literature search was performed in MEDLINE and COCHRANE from 2009 to April 2020.

SELECTION CRITERIA

Studies assessing the diagnostic accuracy of quantitative and/or qualitative ultrasound signs to predict OSB and oPBD were included. Cohort studies and case-control studies were also considered.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed the risk of bias. The overall pooled estimate and a summary receiver operating characteristic curve was estimated for each subgroup (qualitative and quantitative assessment).

MAIN RESULTS

Twenty-three studies were included in our meta-analysis. The pooled sensitivity and specificity for qualitative assessment were 76.5% and 99.6%, and for quantitative assessment were 84.5% and 96.3%, respectively; specificity for the qualitative ultrasound signs was significantly higher (P = 0.001). The overall sensitivity of cranial sonographic markers for the screening of oPBD was 76.7% and specificity was 97.5%.

CONCLUSIONS

The qualitative approach demonstrated greater specificity, so this would appear to be more appropriate for daily screening, as a first-line tool, whereas the quantitative approach should be reserved for expert ultrasound.

TWEETABLE ABSTRACT

This study highlights the relevance of first-trimester qualitative ultrasound signs in the screening of open spina bifida.

Reference ranges for the fetal mesencephalon to occiput measurement at 11 to 13+6 weeks of gestation

The objective was to have a quantitative description of the normal position of the fetal midbrain in the first trimester, through defining the reference ranges for the mesencephalon to the occipital bone distance, in the axial plane. This was a prospective study that included normal fetuses screened between 11 and 13 weeks of gestation. The distance was measured between the posterior limit of the mesencephalon to the occipital bone in the same axial view as the one required for the biparietal diameter (BPD) assessment, at this gestational age (GA). The reference ranges using quantile regression, according to the crown-rump length (CRL), BPD, and GA were fitted. Data analysis included 428 ultrasound measurements. A good, linear correlation was observed between mesencephalon to occiput (MO) distance and CRL, BPD, or GA. It increased linearly with advancing gestation (log₁₀MO = -0.1834 + 0.0092 x CRL, R²=0.48, P<0.0001) and was independent of maternal demographic characteristics and intracranial translucency (IT). In our study, the 1st percentile of the normal MO distance varies from 1.31 mm at a CRL of 45 mm to 2.08 mm at a CRL of 84 mm. The intraclass correlation coefficient (ICC) was 0.89 for intraobserver variability. A significant increase in the MO distance was found in the patients who did not receive folic acid in the first trimester of pregnancy [1.056 vs. 1.008 multiple of median (MoM), P=0.014]. A simple measurement is described between the midbrain and the occipital bone, obtained in the same axial view. It increases linearly with advancing gestation. Integration of this measurement into the routine ultrasound screening in association with the ‘crash sign’ and recognizing the lower extreme values could lead to an early diagnosis of open spina bifida (OSB).