UNASSIGNED: This study aimed to estimate the associations of copy number variants (CNVs) with fetal kidney ultrasound anomalies. A total of 331 fetuses with kidney ultrasound anomalies who underwent prenatal chromosomal microarray analyses were enrolled. The fetuses were classified into groups with isolated and nonisolated anomalies or according to the types of kidney anomalies.
UNASSIGNED: Clinically significant CNVs were identified in 3.4% or 7.3% of fetuses with isolated or nonisolated kidney anomalies, respectively. CNVs were more frequently identified in fetuses with abnormal embryonic migration of the kidneys (6.6%) than in fetuses with malformations of the renal parenchyma (4.7%) or anomalies of the urinary collecting system (3.4%). In particular, CNVs were most frequently detected in fetuses with ectopic kidneys (9.5%) but not in fetuses with horseshoe kidneys or isolated duplex kidneys. Among these CNVs, the most common were del(17)(q12q12) (1.2%) and del(22)(q11q11) (0.6%). The dup(17)(p12p12) and del(15)(q11.2q11.2) CNVs were identified in this study but not in previous studies. The del(X)(p11.4p11.4) and del(16)(p13.3p13.3) CNVs were further implicated as associated with kidney anomalies.
UNASSIGNED: Fetuses with abnormal embryonic migration of the kidneys (particularly ectopic kidneys) showed a higher frequency of clinically significant CNVs, whereas fetuses with horseshoe kidneys or duplex kidneys were less frequently associated with these CNVs.

OBJECTIVE: Restricting studies of severe congenital malformations to live-born children may introduce substantial bias. In this study, we estimated the attendance to the second-trimester fetal malformation screening program. We also estimated the positive predictive value (PPV) of prenatally assigned International Classification of Disease-10 diagnoses recorded in the Danish National Patient Registry (DNPR) and the completeness of case registration. We used kidney anomalies as an example.
METHODS: We identified the proportion of all Danish live-born children from January 1, 2007 to December 31, 2012, who were scanned during the second trimester using the DNPR and the Civil Registration System. Details of all fetuses with specific kidney anomaly diagnoses according to the DNPR were retrieved. The PPV was estimated using the nationwide Astraia database of pregnancy medical charts or traditional medical charts, as gold standard. The completeness was assessed using the total number of cases estimated by the capture-recapture method.
RESULTS: Of 372,263 live born infants, 97.3% were scanned during the second trimester. We identified 172 fetuses in the DNPR. Of these, 149 had kidney anomalies according to Astraia or medical chart review, corresponding to a PPV of 87% (95% CI: 81%-91%). The estimated completeness was 43% (95% CI: 38%-49%) for the DNPR and 75% (95% CI: 70%-79%) for Astraia.
CONCLUSIONS: Almost all live-born children were scanned during the second trimester in Denmark. However, low completeness may hamper the use of the DNPR for studies of prenatally detected severe malformations, and use of the Astraia database may preferably be considered.