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<h3 style="color: black;"><em>Update: July 2023</em></h3><br/>In the Netherlands, all pregnant women are offered prenatal screening for Down, Edwards’ and Patau syndrome (trisomy 21, trisomy 18 and trisomy 13) and for structural anomalies. Currently, the prenatal screening program includes screening for common trisomies through the Non Invasive Prenatal Test (NIPT) from 10 weeks gestation and screening for structural anomalies through an anomaly scan around 13 and 20 weeks of gestation.
This chapter presents uptake of prenatal screening tests and pregnancy outcomes from 2012-2021 for Down, Edwards’ and Patau syndrome and selected structural anomalies. The first trimester anomaly scan was implemented per September 1st 2021 and the combined test (CT) was abandoned per October 1st 2021.
Prenatal screening for congenital anomalies
The prenatal screening program is monitored annually by the regional centers for prenatal screening. The monitoring report (Monitor 2021, Prenatale screening op down-, edwards- en patausyndroom en het Structureel Echoscopisch Onderzoek) can be found at the website of the RIVM. In 2021 in Northeast Netherlands (exceeding the Eurocat NNL region), screening for Down, Edwards’ and Patau syndrome was performed in 10,738 pregnancies through NIPT and in 61 pregnancies through the CT. The uptake was 42.9% for NIPT and 0.3% for the CT. NIPT resulted in 0.5% in a positive result (i.e. indication that fetus is affected with Down, Edwards’ or Patau syndrome). The 20 weeks anomaly scan was performed in 21,293 pregnancies, corresponding with an uptake after counseling of 85.7%. A structural anomaly was suspected in 4.4% of pregnancies. The uptake of the 13 weeks anomaly scan (available from September 1, 2021) was 66%.
Prenatal diagnosis and pregnancy outcome for Down-, Edwards- and Patau syndrome
In 2012-2021 Eurocat NNL registered 500 cases with Down, Edwards’ or Patau syndrome. Total prevalence in this period was 21.4, 7.7 and 2.7 per 10,000 births respectively. Time trends are reported in chapter 6 of the ‘Jaaroverzicht’.
Prenatal diagnosis
Of these 500 cases, 384 (77.6%) were prenatally diagnosed. The proportion of Down, Edwards’ and Patau syndrome cases that were prenatally diagnosed increased during this 10 year period from 62% in 2012 to 89% in 2021 (X2 for trend=15.5, p<0.001; figure 1 and supplementary table). Looking at Down, Edwards’ and Patau syndrome separately, a significant increasing trend was seen for Down syndrome (X2 for trend=12.1, p<0.001), where the proportion of cases with a prenatal diagnosis increased from 49% in 2012 to 86% in 2021. Proportion of prenatally diagnosed cases with Edwards’ or Patau syndrome was high and fluctuated between 86% and 100% (figure 1 and supplementary table).
Figure 1 Proportion prenatally diagnosed cases with Down syndrome and with Edwards’ or Patau syndrome, Eurocat Northern Netherlands 2012-2021.
First positive prenatal test
For the prenatally diagnosed cases we determined what was the first positive prenatal test (defined as first prenatal test whether screening procedure or diagnostic test which indicated a possible congenital anomaly or need for further tests): 1) an increased risk at the CT test or a positive result for NIPT, 2) abnormal findings at ultrasound (US), or 3) positive result at chorionic villus sampling (CVS) or amniocentesis. In 52% of the prenatally diagnosed Down syndrome cases the first positive prenatal test was a positive CT or NIPT, in 45% it was an abnormal finding at US and in 3% it was a positive CVS or amniocentesis. For Edwards’s and Patau syndrome on the other hand, abnormal findings at US accounted for 69%, a positive screening test (CT or NIPT) for 28% and a positive invasive test (CVS or amniocentesis) for 3%.
Table 1 – Prenatal diagnosis, first positive prenatal test and outcome of pregnancy after prenatal diagnosis for Down, Edwards’ and Patau syndrome, Eurocat Northern Netherlands 2012-2021
Down syndrome
Edwards/Patau syndrome
Total cases
335
(100%)
160
(100%)
Prenatally diagnosed
231
(69%)
153
(95.6%)
First positive prenatal test (prenatally diagnosed is 100%)
- Screening test (CT/NIPT)
121
(52.4%)
43
(28.1)%
- Ultrasound
103
(44.6%)
106
(69.3%)
- CVS or amniocentesis
7
(3.0%)
4
(2.6%)
Outcome of pregnancy after prenatal diagnosis (prenatally diagnosed is 100%)
- Live birth
45
(19.5%)
8
(5.2%)
- Fetal death or still birth
19
(8.2%)
19
(12.4%)
- Termination of pregnancy
167
(72.3%)
126
(82.4%)
Outcome of pregnancy overall
Overall, 42% (n=141) of the Down syndrome cases were live born, 8% (n=28) resulted in a fetal death and 50% (n=167) resulted in a termination of pregnancy. For Edwards’ and Patau syndrome, these proportions were 6% (n=10), 16% (n=25) and 81% (n=129) respectively. The live born cases with Edwards’- or Patau syndrome all died after birth.
Outcome of pregnancy after prenatal diagnosis
After prenatal diagnosis of Down syndrome, termination of pregnancy occurred in 72% of the cases, fetal death or still birth occurred in 8% and in 20% there was a live birth (of which 7 (16%) died after birth). For Edwards’ and Patau syndrome the proportions were 82% terminations, 12% fetal deaths and still births and 5% live births (all died after birth).
When the CT or NIPT provided a positive test result followed by a prenatal diagnosis, pregnancy termination occurred in 85% of the Down syndrome cases and in 9% the outcome of pregnancy was a live birth (Figure 2a). When the ultrasound was the first positive test (an ultrasound finding followed by a prenatal diagnosis), termination of pregnancy occurred in 56% of the Down syndrome cases and in 32% there was a live birth. Pregnancy outcome was therefore related to the type of screening test. After a positive CT or NIPT, followed by prenatal diagnosis of Edwards’ or Patau syndrome, termination of pregnancy occurred in 95% of the cases (Figure 2b). When the ultrasound was the first positive test (an ultrasound finding followed by a prenatal diagnosis), termination of pregnancy occurred in 76% of the cases and in 16% there the pregnancy ended in a fetal death or still birth.
Figure 2. Pregnancy outcome for Down syndrome (a) and Edwards/Patau syndrome (b) after a first positive prenatal test, followed by prenatal diagnosis, Eurocat Northern Netherlands 2012-2021
Prenatal diagnosis and pregnancy outcome for structural anomalies (neural tube defects, severe heart defects and abdominal wall defects)
In 2012-2021 Eurocat NNL registered 136 cases with non-chromosomal neural tube defects (NTD), 342 cases with non-chromosomal severe heart defects and 87 cases with non-chromosomal abdominal wall defects. Total prevalence in this period was 8.7, 21.8 and 5.6 per 10,000 births respectively. Time trends are reported in chapter 6 of the ‘Jaaroverzicht’.
Prenatal diagnosis
Prenatal diagnosis occurred in 96% (n=129) of the cases with NTD’s and in 94% (n=81) of the cases with an abdominal wall defect. For severe CHD the proportion prenatally diagnosed was 65% (n=223). (See supplementary table)
First positive prenatal test
For the prenatally diagnosed cases we determined the first positive prenatal test (defined as first prenatal test whether screening procedure or diagnostic test which indicated a possible congenital anomaly or need for further tests) and at what time in pregnancy this ultrasound was performed (before 14 weeks, 14-22 weeks or after 22 weeks). In 33% of the prenatally diagnosed NTD cases an ultrasound in the first trimester, before 14 weeks, was the first positive prenatal test, 66% the NTD was detected at ultrasound between 14 and 22 weeks. For severe CHD the vast majority was detected in the second trimester of pregnancy (91%), whereas for abdominal wall defects about half were detected in the first trimester and half in the second trimester, see table 2.
Table 2 – Prenatal diagnosis, first positive prenatal test and outcome of pregnancy after prenatal diagnosis for neural tube defects, severe heart defects and abdominal wall defects, Eurocat Northern Netherlands 2012-2021
Neural tube defects
Severe heart defects*
Abdominal wall defects
Total cases
134
339
86
Prenatally diagnosed
129
(96.3%)
223
(65.8%)
81
(94.2%)
First positive prenatal test (prenatally diagnosed is 100%)
- Ultrasound 14 weeks
42
(32.6%)
13
(5.8%)
38
(46.9%)
- Ultrasound 14-21 weeks
85
(65.9%)
202
(90.6%)
41
(50.6%)
- Ultrasound 22 weeks
2
(1.6%)
7
(3.1%)
2
(2.5%)
Outcome of pregnancy after prenatal diagnosis (prenatally diagnosed is 100%)
- Live birth (including postnatal mortality)
15
(11.6%)
142
(63.7%)
40
(49.4%)
- Fetal death or still birth
4
(3.1%)
14
(6.3%)
8
(9.9%)
- Termination of pregnancy
110
(85.3%)
67
(30.0%)
33
(40.7%)
* severe heart defects include ICD10 codes Q200 persistent ductus arteriosus, Q201 double outlet right ventricle, Q202 double outlet left ventricle, Q203 complete transposition of great vessels, Q204 single ventricle, Q205 corrected TGA, Q206 isomerism atria, Q212 atrioventricular septal defect, Q213 tetralogy of Fallot, Q214 aortopulmonary window, Q2182 pentalogy of Fallot, Q220 pulmonary valve atresia, Q224 tricuspid atresia, Q225 Ebstein’s anomaly, Q226 hypoplastic right heart syndrome, Q230 congenital stenosis of aortic valve, Q232 congenital mitral stenosis, Q234 hypoplastic left heart syndrome, Q242 cor triatriatum, Q244 subaortic stenosis, Q245 coronary vessel malformation, Q251 coarctatio of aorta,Q252 atresia of aorta,Q253 stenosis of aorta, Q262 total anomalous pulmonary venous connection, Q263 PAPVR
Outcome of pregnancy after prenatal diagnosis
After a prenatal diagnosis of NTD, termination of pregnancy occurred in 85% of the cases, a fetal death or stillbirth occurred in 3% and in 12% there was a live birth (of which 27% (4/15) died after birth). For severe CHD termination of pregnancy occurred in 30% and 64% resulted in a live birth. For abdominal wall defects 41 % were termination of pregnancy and about half were live births. For all three anomalies, termination of pregnancy occurred more frequently when the detection of the anomaly was early in pregnancy, than when the anomaly was detected in the second trimester of pregnancy (figure 3). This is most likely related to the severity of the anomaly.
Figure 3. Pregnancy outcome for neural tube defects (a) and severe heart defects (b) and abdominal wall defects after a first positive prenatal test, followed by prenatal diagnosis, Eurocat Northern Netherlands 2012-2021
Supplementary tables
Number of cases and proportion prenatally diagnosed for Down, Edwards’ and Patau syndrome per birth year, Eurocat Northern Netherlands 2012-2021.
Year of birth
Down syndrome
Edwards- and Patau syndrome
Total (100%)
prenatally diagnosed
Total (100%)
prenatally diagnosed
2012
33
48.5%
17
88.2%
2013
21
66.7%
14
85.7%
2014
35
65.7%
12
91.7%
2015
36
66.7%
8
87.5%
2016
30
60.7%
15
100.0%
2017
31
64.5%
20
100.0%
2018
35
71.4%
24
95.8%
2019
35
77.1%
18
100.0%
2020
43
76.7%
21
100.0%
2021
36
86.1%
11
100.0%
Total
335
69.0%
160
95.6%
Time of diagnosis unknown: Down syndrome (n=1), Edwards’/Patau syndrome (n=4)
Number of cases and proportion prenatally diagnosed for non-chromosomal neural tube defects (NTD), severe congenital heart defects (CHD) and abdominal wall defects per birth year, Eurocat Northern Netherlands 2012-2021.
Year of birth
NTD
Severe CHD
Abdominal wall defects
Total (100%)
prenatally diagnosed
Total (100%)
prenatally diagnosed
Total (100%)
prenatally diagnosed
2012
9
100.0%
37
64.9%
8
87.5%
2013
15
86.7%
33
78.8%
6
100.0%
2014
12
100.0%
42
57.1%
10
100.0%
2015
20
100.0%
31
70.0%
8
100.0%
2016
20
100.0%
27
59.3%
10
90.0%
2017
8
100.0%
43
65.1%
8
75.0%
2018
12
100.0%
33
66.7%
8
100.0%
2019
16
93.8%
36
61.1%
10
100.0%
2020
11
100.0%
30
63.3%
10
100.0%
2021
11
81.8%
30
75.0%
8
87.5%
Total
134
96.3%
339
65.8%
86
94.2%
Time of diagnosis unknown: NTD (n=2), severe heart defects (n=3) and abdominal wall defects (n=1)