Chapter two

Table 1 shows that a total of 13,306 babies with one or more congenital anomalies were notified to NCARDRS in 2019 out of 614,952 total births (live births and stillbirths) in England. This gives an overall birth prevalence of congenital anomalies of 216.4 per 10,000 total births (95% CI: 212.7-220.1). This reflects one baby diagnosed with a congenital anomaly for every 46 births (live births and stillbirths).

Figure 2a and Table 2 shows that the birth prevalence (the number of babies diagnosed with at least one congenital anomaly per 10,000 births) varied by NCARDRS region.

Prevalence was highest in regions with long-established registers (Northern and South West) and lowest in East of England (reporting its second year of data) and in East Midlands and South Yorkshire (EMSY).

Prevalence in the North West region – also reporting its second year of data collection – is significantly higher than the national prevalence and consistent with most existing regions. This reflects increasing ascertainment in a region that has been reporting only since 2018.

NCARDRS has worked with the NHS Fetal Anomaly Screening Programme (FASP) since 2015 in a partnership auditing detection rates for chromosomal, severe cardiac and abdominal wall conditions, along with spina bifida, lethal skeletal dysplasia, Cleft lip +/- palate anencephaly, bilateral renal agenesis and congenital diaphragmatic hernia.

As part of this work, these conditions are subject to more intensive reporting, resulting in higher data quality and ascertainment. While there is regional variation in the overall prevalence of congenital anomalies, Figure 2b shows that prevalence across NCARDRS regions was more consistent when regional prevalence is restricted to babies with one of the 11 FASP conditions. The prevalence in West Midlands and the North West was higher than the NCARDRS average.

Geographical variation in congenital anomaly prevalence is most likely due to differences in case ascertainment due to the infancy of the service and the regional variation in the length of time registration has been established. However there are other reasons which could influence the results presented such as disease clustering, exposure to teratogens, demographic variation including maternal age, deprivation profiles between regions and the composition of the local population.

As NCARDRS accumulates more data at a national level over time, and registration in newer regions matures, greater insights will be gained into underlying population characteristics contributing to regional variation. We will also gain the ability to analyse associations with lifestyle and environmental factors which may potentially be modifiable.

Figure 2a

The number of babies with at least one congenital anomaly per 10,000 total births (prevalence) and 95% confidence intervals for NCARDRS regions compared to England, 2019. The data in this chart can be found in table 2.

Figure 2b

The number of babies with at least one congenital anomaly that is a FASP condition per 10,000 total births (prevalence) and 95% confidence intervals, for NCARDRS regions compared to England, 2019.

Figures 3a and 3b show the prevalence of the 12 major congenital anomaly subgroups for:

a) all babies

b) those that were live born

It is important to note that in Figures 3a, 3b and 3c, babies with multiple anomalies are counted in each applicable bar on the chart. A baby with a congenital heart, limb and chromosomal condition would be represented on 3 different bars. In these figures, conditions categorised as “Genetic” include those babies with an identified chromosomal anomaly, skeletal dysplasia, genetic syndrome and/or microdeletion. Non-genetic conditions include babies with one or more congenital anomaly with no identified anomalies that are chromosomal, skeletal dysplasias, genetic syndromes or microdeletions. Not all babies undergo genetic testing and it is likely some of these “non-genetic” anomalies are of genetic origin.

Figure 3a and Table 1 show that the prevalence for total births in 2019 was highest in the congenital heart anomalies subgroup (62.6 per 10,000, 95% Confidence Intervals (CI) 60.7- 64.6), followed by those that are chromosomal in origin (51.7 per 10,000, 95% CI 49.9-53.5). Figure 3b and Table 3 show that the prevalence for those who are live born was also highest in congenital heart anomalies (51.7 per 10,000, 95% CI 49.9-53.5), followed by the limb anomalies subgroup (26.0 per 10,000, 95% CI 24.8-27.3) and then those that are chromosomal in origin (23.1 per 10,000, 95% CI 22.0-24.4). Not all babies undergo genetic testing and not all babies have the same genetic tests, therefore ‘non-genetic’ cases are those not known to be of genetic origin.

The pattern for all babies diagnosed with a congenital anomaly, and those that are live born, is similar for most subgroups apart from chromosomal and nervous system anomalies. The prevalence in these 2 groups is lower for those live born than for other pregnancy outcomes, reflecting the severity of these conditions. Further detail stratified by specific congenital anomaly, including the number of cases reported, is available in Table 1 and table 3.

More than a third (35.7%) of babies had more than one registered anomaly in 2019. Babies with more than one type of anomaly are counted in each applicable bar in Figures 3a and b. The most frequently detected conditions are congenital heart anomalies and chromosomal anomalies.

Figure 3a

Total birth prevalence: The number of babies diagnosed with each congenital anomaly per 10,000 total births by congenital anomaly subgroup in England, 2019. The data in this chart can be found in table 1. Babies with multiple anomalies will be counted in each applicable bar in figures 3a, b and c.

Conditions categorised as “Genetic” include those babies with an identified chromosomal anomaly, skeletal dysplasia, genetic syndrome and/or microdeletion. Non-genetic conditions include babies with one or more congenital anomaly with no identified anomalies that are chromosomal, skeletal dysplasias, genetic syndromes or microdeletions. Not all babies undergo genetic testing and it is likely some of these are of genetic origin.

Figure 3b

Live birth prevalence: The number of babies diagnosed with each congenital anomaly per 10,000 live births, by congenital anomaly subgroup in England, 2019. The data in this chart can be found in table 3. Babies with multiple anomalies will be counted in each applicable bar in figures 3a, b and c.

Conditions categorised as “genetic” include those babies with an identified chromosomal anomaly, skeletal dysplasia, genetic syndrome and/or microdeletion. Non-genetic conditions include babies with one or more congenital anomaly with no identified anomalies that are chromosomal, skeletal dysplasias, genetic syndromes or microdeletions. Not all babies undergo genetic testing and it is likely some of these are of genetic origin.

NCARDRS achieved national coverage in 2018 when the 3 ‘new’ regions began reporting alongside the ‘existing’ regions that had been collecting data before the formation of NCARDRS. Figure 3c shows the variation in the prevalence of different anomaly groups according to the length of time registration has been established. The prevalence of congenital heart anomalies in existing regions (67.4 per 10,000, 95% CI 64.5-70.4) is still significantly higher than in new regions (58.0 per 10,000, 95% CI 55.4-60.7), reflecting developing ascertainment in these new regions.

Figure 3c also shows that the prevalence of urinary, limb, and genetic syndromes are also significantly lower in new regions compared to those with long-standing registration.

These conditions are more frequently identified postnatally, compared to nervous system, abdominal wall, digestive system, oro-facial cleft, genital, respiratory, chromosomal, and skeletal dysplasia conditions, where the prevalence in new areas was consistent with the prevalence in existing areas. This reflects work with the Fetal Anomaly Screening Programme (FASP) and demonstrates the impact of clinical engagement on data quality. As registration becomes embedded and ascertainment increases, differences in prevalence because of data collection will dissipate, revealing true regional differences, if they exist.

Figure 3c

A comparison of total birth prevalence (the number of babies diagnosed with each anomaly per 10,000 total births) by congenital anomaly subgroup in the existing regions and new reporting regions in England, 2019. Babies with multiple anomalies will be counted in each applicable bar in figures 3a, b and c.

Conditions categorised as “genetic” include those babies with an identified chromosomal anomaly, skeletal dysplasia, genetic syndrome and/or microdeletion. Non-genetic conditions include babies with one or more congenital anomaly with no identified anomalies that are chromosomal, skeletal dysplasias, genetic syndromes or microdeletions. Not all babies undergo genetic testing and it is likely some of these are of genetic origin.

Figure 4 shows that of the 13,306 babies with one or more congenital anomalies, the majority (9,770, 73.4%) resulted in a live birth.

Of the remaining 3,536 babies, 226 (1.7%) were stillbirths (24+ weeks gestation), 80 (0.6%) were late miscarriages (20 to 23 weeks gestation) and 3,230 (24.3%) were terminations of pregnancy. This includes terminations of pregnancy for fetal anomaly (TOPFA) as well as terminations of pregnancy for other reasons, for example social reasons or maternal complications, where a fetal anomaly was present.

The outcome of pregnancy varies according to a range of factors including the severity of the anomaly, co-morbidities, accuracy of screening and practices around termination. The data presented relate to both antenatal and postnatal diagnoses.

The timing of diagnosis is explored in more detail in chapter 3.

Figure 4

Percentage of babies with one or more reported congenital anomalies by outcome of pregnancy in England, 2019. The data in this chart can be found in table 4.

Figure 5 demonstrates the overlap of selected anomalies by presenting the frequency with which severe cardiac and chromosomal anomalies occur in conjunction with other conditions. Of the 1703 babies with severe heart anomalies in 2019 births; 1100 (65.0%) had no other type of anomaly, 362 (21.3%) also had another structural anomaly, which could have included a less severe cardiac anomaly, 363 (21.3%) had a chromosomal anomaly as well as their severe cardiac condition and 145 (8.5%) babies had both a chromosomal anomaly and another structural anomaly in addition to their severe cardiac anomaly.

Figure 5

Multiple anomalies: babies with severe congenital heart disease (CHD), chromosomal and/or other anomalies, in England, 2019.

Severe cardiac anomalies includes the following congenital heart anomalies:

• common arterial trunk
• transposition of great vessels
• single ventricle
• atrioventricular septal defect
• tetralogy of Fallot
• tricuspid atresia and stenosis
• Ebstein’s anomaly
• pulmonary valve atresia
• aortic valve atresia or stenosis
• hypoplastic left heart
• hypoplastic right heart
• coarctation of aorta
• total anomalous pulmonary venous return

(Ref: EUROCAT (2013)