Gastroschisis is a congenital defect of the abdominal wall, characterised by herniation of abdominal viscera outside the abdominal cavity through a defect in the abdominal wall to the side of the umbilicus.1 Recent studies showed an increase in the prevalence of gastroschisis at birth but gave no convincing explanation.2,3 We describe the temporal and geographical variation in this prevalence, using data from the International Clearinghouse For Birth Defects Monitoring Systems, founded in 1974, which fosters sharing information and collaboration among the programmes that monitor birth defects worldwide. Currently, 36 programmes from Europe, the Americas, Asia, Australia, and South Africa participate in the clearinghouse and cumulatively monitor 3.3 million births each year. The head office of the clearinghouse, the International Centre for Birth Defects, registers and evaluates these data.
Participants, methods, and results
We selected registries that provided information on at least 10 consecutive years including 1998 and analysed births occurring between 1974 and 1998 from 19 registries (see bmj.com). The numerators of the prevalences (see table) include liveborn and stillborn babies with gastroschisis (isolated or associated with other defects); denominators are the total numbers of births. Registries used their own diagnostic criteria and definitions of gastroschisis and omphalocele, but we found no substantial differences.
We estimated annual prevalence at birth and 95% confidence intervals from the data and analysed temporal trends using Poisson regression. We used χ2 tests to test for heterogeneity of birth prevalence among registries. We compared the time distributions of gastroschisis and omphalocele by using the Spearman non-parametric correlation test to exclude negative correlations that might suggest shifts in classification of defects from omphalocele to gastroschisis.
The 19 registries recorded 3073 cases of gastroschis. The overall prevalence at birth was 0.29 (95% confidence interval 0.21 to 0.40) per 10 000 births in 1974 and 1.66 (1.51 to 1.85) per 10 000 births in 1998. Prevalences varied among programmes. Nine areas had significant increases in the prevalence of gastroschisis at birth (table 1) from Europe (five registries), Australia, Japan, and the Americas (two registries).
To assess whether such an increase might be explained by a diagnostic shift of the abdominal wall defects, we analysed the time trends of omphalocele in these registries. One registry (Australia) had a mild decrease of omphalocele, three registries had significant increases, and the remaining six registries had no temporal trend. The distributions of gastroschisis and omphalocele over time were not negatively correlated.
Comment
Prevalence of gastroschisis at birth increased in nearly half of the registries studied, beginning at the end of the 1980s in several areas. Such an increase may be even greater than shown here, because of possible under-reporting of cases among selective pregnancy terminations,4 particularly in areas such as France and the Netherlands, where the proportion of selective terminations is high. The increased prevalence of gastroschisis is unlikely to be explained by a systematic shift in the classification of abdominal wall defects. The speed at which the increase has occurred suggests environmental rather than genetic risk factors.
Selective termination and systematic shift in classification should be assessed in a multicentre case-control study. Because children of young mothers are more susceptible to gastroschisis,5 shifts in maternal age distribution should also be investigated. Geographical spread and magnitude show that increased prevalence of gastroschisis at birth is “epidemic.”
Supplementary Material
Table.
Prevalence and 95% confidence intervals of gastroschisis at birth in registries that showed significant increases. Rates are per 10 000 births
| Registry
|
No of cases
|
No of births
|
Earliest
|
Latest
|
PRR (95% CI)
|
|||
|---|---|---|---|---|---|---|---|---|
| Rate (95% CI)
|
Year
|
Rate (95% CI)
|
Year
|
|||||
| Australia | 593 | 4 140 849 | 0.88 (0.42 to 1.62) | 1981 | 2.65 (2.06 to 3.35) | 1997 | 1.08 (1.06 to 1.10) | |
| Finland | 97 | 947 072 | 0.92 (0.33 to 2.00) | 1984 | 1.92 (0.96 to 3.44) | 1998 | 1.11 (1.05 to 1.16) | |
| France (central east) | 180 | 1 932 649 | 0.15 (0.00 to 0.82) | 1978 | 1.46 (0.82 to 2.42) | 1998 | 1.04 (1.01 to 1.06) | |
| France (Paris) | 92 | 659 523 | 0.00 (0.00 to 1.04) | 1981 | 2.69 (1.29 to 4.95) | 1998 | 1.11 (1.07 to 1.16) | |
| Ireland (Dublin) | 30 | 395 528 | 0.00 (0.00 to 1.47) | 1980 | 1.56 (0.30 to 4.58) | 1998 | 1.15 (1.07 to 1.23) | |
| Japan | 361 | 2 931 758 | 1.01 (0.43 to 2.00) | 1974 | 2.28 (1.43 to 3.46) | 1998 | 1.03 (1.02 to 1.05) | |
| Mexico | 161 | 820 987 | 1.20 (0.38 to 2.81) | 1980 | 4.93 (2.87 to 7.90) | 1998 | 1.06 (1.03 to 1.10) | |
| Norway | 265 | 1 403 783 | 0.99 (0.36 to 2.17) | 1974 | 3.07 (1.82 to 4.86) | 1998 | 1.04 (1.02 to 1.06) | |
| South America | 353 | 3 565 511 | 0.12 (0.00 to 0.67) | 1974 | 2.88 (2.07 to 3.90) | 1998 | 1.16 (1.13 to 1.18) | |
PRR=Prevalence rate ratio per annual change according to Poisson regression model.
Footnotes
Funding: No additional funding.
Competing interests: None declared.
Details of contributors are on bmj.com
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