Prenatal screening for congenital abnormalities: role of the 13 week scan

Bardi, F. (Francesca) (2017) Prenatal screening for congenital abnormalities: role of the 13 week scan. thesis, Medicine.

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Abstract

Background and aim The primary aim of this study is to determine the percentage of fetal congenital abnormalities found at the 13 week gross-anatomy survey performed in concomitance of the dating scan or the combined test (CT). Secondly, the research investigates how many and which of the defects observed at the 20 week anomaly scan were not identified by the ultrasound scan performed earlier in gestation. Methods This is a retrospective study performed on a prospectively collected database of consecutive ultrasound scans in a large primary care center in The Netherlands. Pregnancies were included in the study if an ultrasound scan was performed between 11 and 13+6 weeks of gestation and if the estimated date of delivery (EDD) was between 01-01-2012 and 01-01-2016. Pregnancies were excluded from the study when a non-viable fetus was seen at the time of the first scan, or when no information on the second trimester structural anomaly scan (18-22+6 weeks) was available. When an abnormal marker or an anomaly was found at any point during the course of pregnancy, postnatal follow-up outcome was searched for that pregnancy and if this was not present, the case was excluded. Results 10899 pregnancies were included in the study. Mean maternal age and median bodyweight were 30.9 ± 4.7 years and 67 kg (60-76). Of all first trimester scans, 4204 (38.6%) were dating scans and 6685 (61.4%) were CT. At the time of evaluation mean gestational age was 12+1 ± 5 days for dating scans and 12+3 ± 3 days for CTs. Out of all 10889 pregnancies, 196 (1.8%) reported an abnormality; 81 (0.7%) were chromosomal and 115 (1.1%) were structural anomalies diagnosed at first or second trimester scan. NT was increased (NT≥95th percentile) in 364 (5.4%) fetuses who received a CT: 45 (12.4%) of these had a chromosomal anomaly and 12 (3.3%) an isolated structural defect. Also, 15.8% of fetuses affected by cardiac anomalies had an increased NT≥95th. Also, 27% (N=32) of all structural abnormalities were already detected during the first trimester, including all cases of the following: anencephaly (N=4), encephalocele (N=1), exomphalos (N=9), megacystis (N=4) and missing limb (N=1). Detection rate for gastroschisis was 67% (N=2), while heart abnormalities were detected in the first trimester in only 14% of cases (N=3). Conclusions In a primary care setting, a gross anatomical survey performed in concomitance of a dating scan or of the CT, can already detect about 1/3 of all major structural anomalies during the first trimester of pregnancy; especially lethal and very severe defects are identified. Although gross and severe anomalies are already detected by a global survey, as performed during a dating scan, adoption of a systematic protocol and additional training of the sonographers can maximize diagnostic performance to include also less obvious, though severe anomalies. The implementation of an ultrasound scan at 12-13 weeks of gestation, including a protocol for systematic organs visualization, would have important implications for the further refinement and cost-effectiveness of the prenatal screening program in The Netherlands.

Item Type:	Thesis (Thesis)
Supervisor name:	Faculty and daily supervisor and Bilardo, Prof. dr. C.M. and Department and Prenatal diagnosis, Obstetrics & Gynecology
Faculty:	Medical Sciences
Date Deposited:	25 Jun 2020 11:01
Last Modified:	25 Jun 2020 11:01
URI:	https://umcg.studenttheses.ub.rug.nl/id/eprint/2097

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