This study investigated the presence of human Norovirus (HuNoV) by genotype in 1,486 groundwater samples, collected from 843 groundwater wells suspected of contamination during 2007-2016, in Republic of Korea. We identified and genotyped 186 HuNoV sequences in 178 HuNoV-positive samples using the RIVM-NoroNet norovirus genotyping tool (NGT) and phylogenetic tree analysis based on RIVM-NoroNet reference sequences. HuNoV GII was more prevalent than GI. The major genotypes detected were HuNoV GII.4 (43.0%), GII.22 (15.6%), GI.5 (10.2%) and GI.1 (8.6%); 14 genotypes accounted for < 5.0%. Increasing HuNoV GII.17 has displayed a worldwide trend, including in Europe and Asia since 2010, and it was the dominant HuNoV genotype during 2013-2014 in Korea. However, HuNoV GII.4 was the major genotype detected in groundwater in Korea in 2015-2016, and it is becoming increasingly prevalent similar to HuNoV GII.17.

Objectives: To assess clinical implications of increased nuchal translucency (INT) in twin pregnancies based on the chorionicity. Methods: This was a retrospective review of the twin pregnancies who underwent first trimester ultrasound with nuchal translucency (NT) measurement at 11-13 weeks of gestation from January 2006 to December 2014. Data were collected using the OB database and the chart review. Pregnancy outcomes including gestational weeks at the delivery, abnormal fetal karyotypes, fetal structural anomalies, twin specific complications were analyzed. Results: A total of 1,622 twin pregnancies with INT≥95th percentile in one or both fetuses were identified. In all twin pregnancies with INT, abnormal fetal karyotypes were identified in 17 (8.6%) patients (odds ratio=13.28, CI=5.990-29.447, P=0.000) and twin-specific complications were identified in 23 (11.6%) patients (odds ratio=2.398, CI=1.463-3.928, P=0.001) compared to those with normal NT. Among the INT group, when the groups were subdivided into monochorionic (MC) and dichorionic (DC) pregnancies, 14.8% and 29.6% of the MC pregnancies had structural anomalies in one or both fetuses (odds ratio=5.774, 95% CI=1.445-23.071, P=0.01) and twin-specific complications (odds ratio=4.379, 95% CI=1.641-11.684, P=0.03), respectively, compared to DC pregnancies. The prevalence of abnormal fetal karyotypes was not statistically different in patients with INT when compared between MC and DC pregnancies (P=0.329). Conclusions: INT was associated with a higher rate of twin-specific complications and fetal structural anomalies in MC twin pregnancies rather than abnormal fetal karyotype. Therefore, NT measurement in MC twin pregnancies can be a useful tool for prediction of adverse pregnancy outcomes. Appropriate counseling and surveillance based on the chorionicity is imperative in prenatal care of twin pregnancies.

Background The purpose of this study was to evaluate the prevalence of velamentous cord insertion (VCI) and the actual association between pathologically confirmed VCI and perinatal outcomes in twins based on the chorionicity. Methods All twin pregnancies who received prenatal care at a specialty clinic for multiple pregnancies, from less than 12weeks of gestation until delivery in a single institution between 2015 and 2018 were included in this retrospective cohort study. Results A total of the 941 twins were included in the study. The prevalence of VCI in dichorionic (DC) twins and monochorionic diamniotic (MCDA) twins was 5.8% and 7.8%, respectively (p=0.251). In all study population, the prevalence of vasa previa and placenta accreta were higher in VCI group compared to that of non-VCI group (p=0.008 and 0.022). In MCDA twins with VCI, birth weight, 1 and 5-minute Apgar score were lower compared to DC twins with VCI (p=0.010, 0.002 and 0.000). There was no significant association between VCI and selective fetal growth restriction (p=0.708), twin-to-twin transfusion syndrome (p=0.400) and birth-weight discordance (>20% and >25%) (p= 0.378 and 0.161) in MCDA twins. Conclusion VCI in twins was not a risk factor for adverse perinatal outcomes and twin-specific complications.