Papers

Prevalence of gastroschisis at birth: retrospective study

Gian Luca Di Tanna, senior statistician ^a, Aldo Rosano, senior researcher ^b, Pierpaolo Mastroiacovo, director ^a. 

^a International Centre for Birth Defects, 00195 Rome, Italy, ^b Italian Institute of Social Medicine, 00196 Rome

Correspondence to: P Mastroiacovo
icbd{at}icbd.org

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

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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 ² 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

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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."

	Acknowledgments

Contributors: GLDT designed the study, managed and analysed the data, and participated in drafting the paper. AR projected and designed the study, interpreted the data, and participated in drafting the paper. PM revised the paper. PM is guarantor.

	Footnotes

Funding: No additional funding.

Competing interests: None declared.

Details of contributors are on bmj.com

	References

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2.	Tan KH, Kilby MD, Whittle MJ, Beattie BR, Booth IW, Botting BJ. Congenital anterior abdominal wall defects in England and Wales 1987-93: retrospective analysis of OPCS data. BMJ 1996; 313: 903-906[Abstract/Free Full Text].
3.	Rankin J, Dillon E, Wright C. Congenital anterior abdominal wall defects in the north of England, 1986-1996: occurrence and outcome. Prenat Diagn 1999; 19: 662-668[CrossRef][Web of Science][Medline].
4.	Barisic I, Clementi M, Hausler M, Gjergja R, Kern J, Stoll C. Evaluation of prenatal ultrasound diagnosis of fetal abdominal wall defects by 19 European registries. Ultrasound Obstet Gynecol 2001; 18: 309-316[CrossRef][Medline].
5.	Nichols CR, Dickinson JE, Pemberton PJ. Rising incidence of gastroschisis in teenage pregnancies. J Matern Fetal Med 1997; 6: 225-229[CrossRef][Medline].

(Accepted 25 June 2002)