The "cortical invagination sign": a midtrimester sonographic marker of unilateral cortical focal dysgyria in fetuses with complete agenesis of the corpus callosum

BACKGROUND

Agenesis of the corpus callosum is associated with several malformations of cortical development. Recently, features of focal cortical dysgyria have been described in fetuses with agenesis of the corpus callosum.

OBJECTIVE

This study aimed to describe the "cortical invagination sign," a specific sonographic feature of focal cortical dysgyria, which is consistently seen at midtrimester axial brain ultrasound in fetuses with complete agenesis of the corpus callosum.

STUDY DESIGN

This was a retrospective analysis of prospectively collected data from 2018 to 2021, including patients referred to 5 fetal medicine centers in the second trimester of pregnancy (19 0/7 to 22 0/7 weeks of gestation) with suspected complete agenesis of the corpus callosum. All cases with the diagnosis of complete agenesis of the corpus callosum were submitted to an axial sonographic assessment of the fetal brain on the transventricular plane. In this scanning section, the mesial profile of both cerebral hemispheres at the level of the frontal-parietal cortex was investigated. In this area, the operator looked for an abnormal invagination of the cortical surface along the widened interhemispheric fissure, which was referred to as the "cortical invagination sign." All fetuses were submitted to dedicated antenatal magnetic resonance imaging to reassess the ultrasound findings. Cases with additional brain anomalies, which did not involve the cortex, were excluded. The final diagnosis was confirmed at postnatal brain magnetic resonance imaging or postmortem examination, for cases undergoing termination of pregnancy. The primary outcome of this study was to evaluate the presence and laterality of the "cortical invagination sign" in fetuses with complete agenesis of the corpus callosum at antenatal ultrasound and magnetic resonance imaging.

RESULTS

During the study period, 64 cases of complete agenesis of the corpus callosum were included; of those cases, 50 (78.1%) resulted in termination of pregnancy, and 14 (21.9%) resulted in a live birth. The "cortical invagination sign" was detected at ultrasound in 13 of 64 cases (20.3%) and at targeted brain magnetic resonance imaging in 2 additional cases (23.4%), all of which were electively terminated. Moreover, the "cortical invagination sign" was found to be exclusively unilateral and on the left cerebral hemisphere in all the cases. There was a predominant number, although nonsignificant, of male fetuses (80.0% of cases; P=.06) in the group of complete agenesis of the corpus callosum with the "cortical invagination sign."

CONCLUSION

The "cortical invagination sign" is a specific marker of focal cortical dysgyria, which seems to characterize at midtrimester of pregnancy in a large group of fetuses with complete agenesis of the corpus callosum. The etiology, pathophysiology, and prognostic significance of this finding remain to be elucidated.

Risk factors and perinatal outcomes for persistent placenta previa in nulliparas

BACKGROUND

Placenta previa diagnosed on midtrimester ultrasound often resolves by the third trimester. Multiparity and previous cesarean delivery have been associated with persistence of placenta previa at delivery. Risk factors for persistent placenta previa in nulliparas are not well characterized.

OBJECTIVE

This study aimed to identify risk factors for persistent placenta previa in the nulliparous population, and evaluate differences in outcomes between persistent and resolved placenta previa.

STUDY DESIGN

This was a secondary analysis of the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-be (nuMoM2b), a prospective cohort study that observed 10,037 nulliparous individuals throughout pregnancy. Nulliparas diagnosed with placenta previa on midtrimester ultrasound were included in this analysis. Baseline characteristics and delivery outcomes of nulliparas with persistent placenta previa were compared with those of nulliparas with resolved placenta previa. Multivariate logistic regression with stepwise model selection was used for adjusted analyses.

RESULTS

A total of 171 nulliparas (1.7%) in the nuMoM2b study were diagnosed with placenta previa on midtrimester ultrasound, of whom 17% (n=29) had persistent placenta previa at delivery. When compared with those with resolved placenta previa, nulliparas with persistent placenta previa were more likely to be older (median, 32 years [interquartile range, 30-37] vs 29 years [interquartile range, 25-31]; P<.01), have a previous pregnancy of <20 weeks (48.3% vs 22.5%; P=.01), have a previous dilation and curettage/evacuation procedure (27.6% vs 10.6%; P=.03), or have a pregnancy that resulted from assisted reproductive technology (31% vs 4.9%; P=.01). After adjusting for potential confounders, maternal age (adjusted odds ratio, 1.11; 95% confidence interval, 1.02-1.21), in vitro fertilization (adjusted odds ratio, 9.00; 95% confidence interval, 1.97-41.14), and previous pregnancy of <20 weeks (adjusted odds ratio, 2.77; 95% confidence interval, 1.10-6.95) remained statistically significant risk factors for persistent placenta previa. Persistent placenta previa was also associated with higher likelihood of antepartum admission (10.3% vs 0%; P<.01), preterm delivery (34.5% vs 12%; P<.01), lower neonatal birthweight (median, 2847 g [interquartile range, 2655-3310] vs 3263 g [interquartile range, 2855-3560]), and cesarean delivery (100% vs 20.4%; P<.001), but there were no differences in overall pregnancy or neonatal outcomes.

CONCLUSION

In nulliparous individuals diagnosed with placenta previa on midtrimester ultrasound, older maternal age, previous pregnancy of <20 weeks, and in vitro fertilization are associated with persistent placenta previa at delivery.

Midtrimester Ultrasound Predictors of Small-for-Gestational-Age Neonates

OBJECTIVES

To determine whether a specific estimated fetal weight (EFW) or abdominal circumference (AC) measurement percentile at the 18-to 24-week ultrasound (US) examination is associated with a small-for-gestational-age (SGA) neonate.

METHODS

A retrospective case-control study was conducted including women with uncomplicated singleton gestations who delivered a term SGA neonate identified as having a birth weight (BW) below the 10th percentile on the Olsen growth curve and had an 18- to 24-week US examination in our database. The study period was October 2011 to January 2018. A similar number of control charts were requested randomly over the same time with BW in the 10th to 90th percentiles, all which had an 18-to 24-week US examination in our database. After all neonates meeting BW criteria were identified, a chart review was performed to specifically evaluate biometric parameters from the US at 18 to 24 weeks to determine a potential correlation with the EFW percentile and AC percentile. Pregnancy, neonatal outcomes, and maternal demographic characteristics were collected.

RESULTS

A total of 549 term neonates with a BW below the 10th percentile, and 593 control term neonates with BW in the of 10th to 90th percentiles were reviewed. Our analyses revealed that the AC and EFW percentiles were poor predictors of BW (<10th percentile; areas under the receiver operating characteristic curves, 0.68 and 0.69, respectively). A similar low ability of AC and EFW to predict BW below the 5th percentile was noted.

CONCLUSIONS

(1) No tipping point or cutoff for the EFW or AC percentile at the 18- to 24-week US examination was identified to predict a term SGA neonate. (2) These data are helpful when counseling women in midgestation about specific parameters, their importance, and the potential need for follow up imaging.

Amniotic fluid sludge as a marker of intra-amniotic infection and histological chorioamnionitis in cervical insufficiency: a report of four cases and literature review

Amniotic fluid sludge (AFS) is defined as the presence of particulate matter in the amniotic fluid in close proximity to the cervix. Although its prevalence is known to correlate with the risk of preterm delivery, initial reports describe a strong association between AFS and microbial invasion of the amniotic cavity (MIAC) and histological chorioamnionitis. However, AFS is also present in uncomplicated pregnancies, and its prevalence appears to increase with gestational age. Recent evidence debates the usefulness of AFS as a marker of early preterm delivery risk. We present four cases with AFS diagnosed by transvaginal ultrasound at admission for cervical insufficiency between 20 and 24 weeks of gestation, with confirmed lower genital tract and intra-amniotic infections by amniocentesis and histological chorioamnionitis and funisitis. Our findings reinforce the presence of AFS as a useful marker of MIAC, chorioamnionitis and funisitis that increase the likelihood of preterm delivery at an extreme gestational age.