Chapter four

There were 633 infant deaths among babies with one or more congenital anomalies in the 612,606 live births in 2019, giving an infant mortality rate of 10.3 per 10,000 live births. Table 8 shows that the rate of perinatal mortality was 7.7 per 10,000 births.

Mortality definitions:

Infant mortality refers to deaths under one year of age.

Perinatal mortality refers to stillbirths and deaths under 7 days of age.

Figures 9a and 9b show that in cases of both perinatal and infant mortality, the most frequently recorded anomalies were the same; congenital heart anomalies (2.6-perinatal, 5.4-infant per 10,000 births respectively) followed by chromosomal (2.2-perinatal, 2.4-infant per 10,000 births respectively). The data presented here should be viewed with some caution, as babies with more than one anomaly will appear in each anomaly subgroup. Additionally, a link between the presence of a congenital anomaly and the cause of death has not been established, therefore it is possible that the identified congenital anomaly had no bearing on mortality. These figures also do not include conditions with a high level of antenatal mortality, pregnancy loss or rate of TOPFA, where few pregnancies result in either a live birth or stillbirth, for example, anencephaly.

Figure 9a

Perinatal mortality (stillbirths and deaths under 7 days of age) by congenital anomaly subgroup in England, 2019. The data in this chart can be found in table 8.

Figure 9b

Infant mortality (deaths under one year of age) by congenital anomaly subgroup in England, 2019. The data in this chart can be found in table 8.

Child and infant mortality data from the ONS for 2019 shows that congenital anomalies were the most common cause of death in the post neonatal period, accounting for 39.3% of deaths. Congenital anomalies were also listed as the cause of 32.3% of infant deaths and 24.0% of perinatal deaths, the second highest cause in both categories after prematurity. While the data within this report should be viewed in a wider context of perinatal and infant mortality, congenital anomalies, particularly congenital heart, chromosomal and digestive system anomalies, are a common factor in infant and perinatal deaths.

There was a U-shaped relationship with maternal age. Table 9 shows that mothers under 20 years had a significantly higher rate of congenital anomalies compared to those aged between 30 and 34 years. The birth prevalence of all anomalies was similar in mothers aged between 30 and 34 years at delivery compared to the prevalence in those aged between 25 and 29 years (195.9 and 195.3 per 10,000 total births respectively). Compared to these groups, the birth prevalence was significantly higher in mothers aged 35 to 39 years (243.7 per 10,000 total births) and those 40 years and over (399.3 per 10,000 total births).

The association between higher maternal age and certain genetic disorders, including Down’s syndrome, is well established. Figure 10 shows that mothers aged 40 and over had a significantly higher prevalence of genetic anomalies compared to all other age groups. The rate of genetic congenital anomalies in women over 40 years (n=622) was almost 9 times higher (8.5 95% CI 6.3-11.6) relative to women under 20 years (n=41). Down’s syndrome is the most common genetic anomaly (25.4 per 10,000 births) and is likely a primary factor in the higher rate in older age groups.

Figure 10 and Table 9 show that the rate of non-genetic anomalies in women aged under 20 years is significantly higher than the rate in women between 25 to 39 years. The increased rate in mothers under 20 years is primarily driven by the significantly higher prevalence of abdominal wall anomalies in women within this age group (24.0 per 10,000 births) compared to 5.4 per 10,000 births in women aged 30 to 34 years.

Gastroschisis, an abdominal wall anomaly, is known to be associated with lower maternal age (Baldacci and others 2020; Fillingham and Rankin 2008), and this relationship is demonstrated within Figure 11 as the prevalence among those under 20 is 20.4 per 10,000 births compared to 0.8 per 10,000 births in women aged between 35 and 39. There were no babies with gastroschisis recorded in women aged over 40 in England in 2019.

Figure 10

Prevalence (per 10,000 total births) and 95% confidence intervals of genetic and non-genetic congenital anomalies by maternal age in England, 2019. The data in this chart can be found in table 9.

Figure 11

Prevalence (per 10,000 total births) and 95% confidence intervals of gastroschisis by maternal age in England, 2019.