Osamu Samura

Non-invasive prenatal testing (NIPT) is a screening method that detects fetal chromosomal trisomies from cell-free DNA in maternal blood. Because NIPT uses whole-genome sequencing with next-generation sequencing for data processing, it can also detect maternal genomic information. Although most copy number variations (CNVs) are benign, some have been reported to be associated with pathological phenotypes and are attracting increasing attention. However, most CNV studies have been conducted in Western populations, and large-scale studies in Japanese cohorts remain scarce. This study represents the first multicenter, large-scale cohort investigation of maternal CNVs in Japanese pregnant women. We analyzed 46,082 participants to establish a reliable threshold for maternal CNV detection and to evaluate their clinical significance. Maternal CNVs were validated using array comparative genomic hybridization, and receiver operating characteristic curve analysis identified 0.8 Mbp as the minimum threshold achieving 100% specificity. Applying this criterion, maternal CNVs were identified in 2907 cases (6.3%), with the most frequent being a duplication at chr8: 3,842,478-6,092,478 (hg38, allele frequency 2.67%). Comparison with public genomic databases, including the Tohoku Medical Megabank Organization (ToMMo) and the Genome Aggregation Database (gnomAD), confirmed that all CNVs detected in this study had been previously reported, with particularly high concordance in ToMMo. Notably, several very rare CNVs were also identified. These findings demonstrate that NIPT can reliably detect maternal CNVs ≥0.8 Mbp, which appear to represent benign genomic variants that are unlikely to affect fertility or early miscarriage.

Objective: This study aimed to investigate the association between fetal fraction (FF) on non‐invasive prenatal testing (NIPT) and pregnancy‐related complications using a large sample to support improved prenatal management. Methods: This retrospective cohort study included women with singleton pregnancies and negative NIPT results between January 2015 and March 2022 as part of the Japan Multicenter Study. Chi‐square tests and binary logistic regression analyses were used to assess the association between FF and pregnancy‐related complications. Results: A total of 40,716 responses were analyzed. No significant association was found between FF and placental abruption (χ ² (1) = 2.84, p = 0.09). Women in the low FF group (FF < 10.27%, < 25th percentile) had higher risks of fetal demise, adjusted OR = 1.79, 95% CI [1.31, 2.43]), preterm birth (adjusted OR = 1.63, 95% CI [1.30, 2.06]), fetal growth restriction (FGR) (adjusted OR = 1.50, 95% CI [1.10, 2.05]), and hypertensive disorders of pregnancy (HDP) (adjusted OR = 1.44, 95% CI [1.24, 1.66]). No significant differences were observed for gestational diabetes mellitus (GDM) (adjusted OR = 1.13, 95% CI [0.99, 1.30], p = 0.081). Conclusion: Low FF on NIPT is associated with an increased risk of several pregnancy complications, highlighting the need for careful management.

Non-invasive prenatal testing (NIPT) enables the screening of fetal chromosomal abnormalities by analyzing cell-free DNA (cfDNA) in maternal blood. Recent technological advancements have expanded its applications to the detection of copy number variations (CNVs). However, the clinical utility of CNV detection remains unclear. We aimed to investigate the association between fetal CNVs detected by genome-wide NIPT and perinatal outcomes in a large cohort in Japan. This retrospective cohort study included 46,082 patients who underwent NIPT at certified facilities in Japan between January 2015 and September 2021. Genome-wide NIPT was performed using massively parallel sequencing to detect fetal CNVs exceeding 7 Mb. Despite their small size, well-characterized microdeletions, such as 22q11.2 were included. From 46,082 patients with NIPT results, 30,373 cases with known birth outcomes were extracted, and cases with fetal CNV were included in the analysis. Fetal CNVs were detected in 66 patients (0.2%). Adverse outcomes, including miscarriage, growth restriction, and structural abnormalities, were observed in 14 of the 66 cases (21.2%). Pathogenic CNVs were frequently detected even in the 52 cases (78.8%) with favorable outcomes. Genome-wide NIPT may assist in the diagnosis of cases with structural abnormalities when combined with confirmatory testing. Our findings demonstrate that pathogenic CNVs are also detected in a substantial number of structurally normal fetuses with favorable short-term outcomes. This discordance presents a significant challenge for prenatal counseling. The clinical significance of the findings should be clarified through confirmatory testing of CNV cases and the accumulation of data from long-term follow-up studies.

Background/Objective: Early pregnancy loss is often caused by chromosomal abnormalities, necessitating accurate diagnostic tools. While product of conception (POC) chromosomal testing is commonly used, it can be limited by culture failure or an inability to obtain fetal tissue due to spontaneous expulsion. Cell-free fetal DNA (cff DNA) analysis provides a non-invasive alternative; however, its effectiveness in early pregnancy loss, particularly in cases where fetal components are still minimal, has not been fully established. The objective of this study was to evaluate the accuracy of pre- and postoperative cff DNA analysis for detecting fetal aneuploidy by comparing the results to those of POC chromosomal testing. Methods: In this single-center prospective cohort study, 50 women undergoing manual vacuum aspiration for pregnancy loss before 12 weeks of gestation were enrolled (February 2022–December 2024). Cff DNA analysis was performed on maternal blood samples collected pre- and postoperatively. The primary outcome was concordance between the cff DNA and POC results. Sensitivity, specificity, and factors affecting concordance were also assessed. Results: Eight participants were excluded due to unsuccessful POC culture (n = 3), suspected maternal tissue contamination in the POC sample (n = 1), mosaicism (n = 3), or triploidy (n = 1), resulting in 42 evaluable cases. Preoperative cff DNA analysis showed 88.1% concordance with POC (sensitivity 86.4% and specificity 90.0%). Postoperative analysis showed 78.6% concordance (sensitivity 72.7% and specificity 85.0%). Conclusions: The Cff DNA analysis of preoperative and postoperative maternal blood samples showed generally good concordance with conventional POC chromosomal testing in detecting fetal aneuploidy in early pregnancy loss.

Determining the differential diagnosis of small scalp cysts identified on a fetus is difficult. In particular, many physicians have difficulty differentiating small meningoceles from small scalp cysts during the prenatal period. Volume contrast imaging increases contrast between tissues, thereby allowing an enhanced view of target structures. A 15 × 5 mm scalp cyst was identified on a fetus during a prenatal ultrasonography examination performed at 20 weeks of gestation. The cyst was not connected to the blood flow, and did not include the tissue of the brain parenchyma. Ventriculomegaly and other structural abnormalities were not observed. Based on these findings, we suspected a sinus pericranii or fetal epidermal cyst. The size of the fetal scalp cyst was stable, and the growth of the fetus remained normal until birth. The diagnosis of a small meningocele was confirmed postnatally, based on the results of a magnetic resonance imaging examination. Postnatal evaluation of offline volume contrast imaging of prenatal three‐dimensional ultrasound data at 22 weeks of gestation revealed a skull bone defect beneath the cyst. Volume contrast imaging can facilitate the prenatal diagnosis of small meningoceles by detecting bone defects on the fetal head.

Type 2 spinal muscular atrophy with lower extremity dominance (SMALED2) is caused by bicaudal D cargo adaptor 2 (BICD2) variants. However, the SMALED2 genotype and phenotype correlation have not been thoroughly characterized. We identified de novo heterozygous BICD2 missense variants in two fetuses with severe, prenatally diagnosed multiple arthrogryposis congenita. This report provides further insights into the genetics of this rare disease.

Aim: In Japan, noninvasive prenatal testing (NIPT) has been performed by facilities accredited by the Japanese Society of Obstetrics and Gynecology since 2013. However, since 2016, with the implementation of NIPT, which can only be performed by blood sampling, non‐obstetricians have been involved in prenatal testing. Therefore, in July 2022, a new government‐involved NIPT certification system based on Health Sciences Council guidelines was introduced to ensure access to prenatal testing information for pregnant women. Methods: This survey was conducted in February 2023 and was the first survey after the certification system implementation. We conducted a web‐based survey of 1227 pregnant women and nursing mothers who underwent NIPT after July 2022 to evaluate their experiences. Results: Respondents were categorized by certification status as certified (C: 56%), non‐certified (non‐C: 23%), or uncertain (Q: 20%). The C group with a higher mean age at examination (35.0 ± 4.5 years) paid lower examination fees, received longer pre‐ and post‐examination explanations, and underwent more weekday examinations (80%) than the other groups. Most respondents, 67%, 48%, and 53% in the C, non‐C, and Q groups, respectively ( p < 0.0001), stated that “NIPT needs to be regulated by the government or academic societies.” The non‐C group was more likely to say, “Insufficient post‐test explanations at the laboratory made me more anxious,” than the other groups when the testing results were non‐negative ( p = 0.015). Conclusions: Despite government regulation, some pregnant women choose convenience over certified facilities, risking inadequate care. The government should ensure that NIPT is a safe option for all pregnant women.

Angiotensin II receptor blockers (ARBs) are contraindicated during pregnancy because of fetal toxicity. All previous reports on adverse fetal outcomes involved women who continued to take low‐dose ARBs for hypertension and were unaware of the adverse effects. Herein, we report the case of a 23‐year‐old pregnant woman in her third trimester who experienced an ARB overdose after an argument with her partner. Pregnancy was complicated by transient oligohydramnios, and fetal magnetic resonance imaging suggested renal failure. Despite these concerns, the newborn had no morphological abnormalities or abnormal neurological findings. Renal impairment improved over time, and the infant grew well. A single overdose of ARBs in the third trimester can lead to fetal renal failure, similar to long‐term low‐dose ARB administration; however, favorable outcomes are possible. An overdose of ARBs may transiently cause renal failure, which may improve. The study findings may inform counseling for women who are unexpectedly exposed to an overdose of ARBs.

A woman in her 30s at 29 weeks of gestation was diagnosed with a fetal abdominal cyst and polyhydramnios. As the cyst gradually increased in size, an elective caesarean section was performed at 38 weeks of gestation. The neonate experienced respiratory distress due to tense abdominal distension shortly after birth. An emergency laparotomy was performed. The intestinal tract was markedly dilated and contiguous with the cyst. The small bowel distal to the dilated intestine had herniated through the defect. The dilated segment was resected, and an ileostomy was created. The operative and histopathological findings suggested segmental dilatation of the intestine (SDI). SDI is a rare gastrointestinal disorder presenting during the neonatal period. It can cause respiratory failure in newborns by compression owing to its large size. SDI should be considered in the differential diagnosis of relatively large abdominal cysts, and collaboration with paediatric surgeons and neonatologists is necessary for successful outcomes.