www.elsevier.com/locate/jpedsurg

Journal of Pediatric Surgery (2009) 44, 551–555

Rising incidence of gastroschisis and exomphalosin New ZealandVijay Srivastavaa, Parkash Mandhana, Kevin Pringleb, Philip Morreauc,Spencer Beasleyd, Udaya Samarakkodya,⁎

aDepartment of Pediatric Surgery, Waikato Hospital, Hamilton 2240, New ZealandbDepartment of Pediatric Surgery, Wellington Hospital, Wellington 6021, New ZealandcDepartment of Pediatric Surgery, Starship Children's Hospital, Auckland 1023, New ZealanddDepartment of Pediatric Surgery, Christchurch Hospital, Christchurch 8011, New Zealand

Received 26 September 2008; accepted 26 September 2008

0d

Key words:Anterior abdominalwall defects;

Gastroschisis;Exomphalos;Omphalocele;Incidence

AbstractBackground: An apparent increase in the incidence of gastroschisis and exomphalos has been reportedfrom several parts of the world. The exact mechanism of this trend is unknown. The aim of this studywas to determine the regional and national trends in the incidence of gastroschisis and exomphalos inNew Zealand.Material and Methods: This retrospective multicenter study involved collection of data from all4 tertiary care pediatric surgical centers in New Zealand. The incidence was calculated per 10,000 livebirths. Data were analyzed to determine the regional and national trends. The statistical analysis wasdone using linear regression model and Poisson distribution.Results: The incidence of gastroschisis has increased from 2.96 per 10,000 live births to 5.16 per 10,000live births between 1996 and 2004. During the same period, the incidence of exomphalos has increasedfrom 0.69 per 10,000 live births to 3.27 per 10,000 live births. Gastroschisis was observed more inyounger mothers, whereas exomphalos was associated with older mothers.Conclusion: The incidence of gastroschisis and exomphalos is increasing in New Zealand, whichis consistent with worldwide trends in showing the increasing incidence of anterior abdominalwall defects.© 2009 Elsevier Inc. All rights reserved.

Gastroschisis and exomphalos are the 2 most common is usually small and to the right of umbilicus [1,2].

congenital malformations of anterior abdominal wall. Thesedefects are clinically different and pose challengingproblems for management. Embryologically, gastroschisisis caused by regression of omphalomesenteric arteriesconnecting the yolk sac to the dorsal aorta, and the defect

⁎ Corresponding author. Tel.: +64 7 839 8765; fax: +64 7 839 8716.E-mail address: samaraku@waikatodhb.govt.nz (U. Samarakkody).

022-3468/$ – see front matter © 2009 Elsevier Inc. All rights reserved.oi:10.1016/j.jpedsurg.2008.09.025

Exomphalos is caused by defective inbody folding at 3 to4 weeks of gestation and the failure of the return of intestineto abdominal cavity at 12 weeks. The size of the defect variesfrom small to large [2].

The generally accepted incidence of gastroschisis is about1 per 10,000 live births and that of exomphalos is 2 to 2.5 per10,000 live births [3,4]. For the last 2 decades, studies fromEurope, United States, Japan, South Africa, and Australia

Fig. 1 The national incidence (per 10,000 live births) ofgastroschisis and exomphalos in New Zealand.

552 V. Srivastava et al.

[5-14] have shown an increasing trend of gastroschisisalthough it is not a universal finding [15,16]. Exomphaloshas also seen an increasing trend in countries such as Japan,although some studies indicate that its incidence hasremained stable in contrast to gastroschisis [10,12].

The aim of this national study was to look into thenational and regional trend in the incidence of gastroschisisand exomphalos in New Zealand.

1. Patients and methods

This retrospective multicenter study (1991-2004) con-sisted of data collection from 4 tertiary pediatric surgicalcenters in New Zealand (Hamilton, Auckland, Christchurch,and Wellington). All cases of gastroschisis and exomphalosborn in or referred to these centers were included. Bothexomphalos major and minor were included with omphalo-cele in the study. The data were collected from multiplesources, which include hospital databases, clinical codingdepartment, and the newborn intensive care units. Data fromHamilton center were further cross-checked with the patientnotes, and the Christchurch data were checked against thedepartmental audit database. The population data and the livebirth data were gathered from New Zealand Statistics and theMinistry of Health. The incidence was calculated as per10,000 live births. The data analysis was carried out todetermine the national and regional trends. Statisticalmethods to analyze data included linear regression modeland Poisson distribution to establish the statistical signifi-cance of apparent trends.

2. Results

For the 14 years, 351 cases of gastroschisis andexomphalos in 4 tertiary care centers (Hamilton, Auckland,Wellington, and Christchurch) of New Zealand wereidentified. Of these, Hamilton center had 51 gastroschisisand 28 exomphalos cases and Auckland center had 98gastroschisis and 59 cases of exomphalos during the sameperiod. The data were not available for 1991 and 1992 inWellington or before 1996 in Christchurch when the pediatricsurgical service commenced. Wellington center had 42 casesof gastroschisis and 17 cases of exomphalos for a 12-year

Table 1 Distribution of gastroschisis and exomphalos cases inaccordance with the maternal age

Centre b20 y 20-25 y 25-30 y N35 y

G Ex G Ex G Ex G Ex

Hamilton 18 2 30 15 8 7 1 4Auckland 36 6 47 33 14 13 1 7Wellington 7 3 24 8 10 3 1 3Christchurch 6 2 20 7 9 2 2 2

G indicates gastroschisis; Ex, exomphalos.

period (1993-2004). Christchurch center had 37 cases ofgastroschisis and 13 cases of exomphalos for a 9-year period(1996-2004).

The median maternal age is increasing in New Zealand.The median maternal age in New Zealand was 30.3 years inDecember 2004 compared with 28.5 years in 1994 and 24.9years in 1974 [17]. The distribution of cases in accordancewith maternal age is shown in Table 1. The mean maternalage was 21 years (range, 16-39 years) for gastroschisis and26 years (range, 17-38 years) for exomphalos. In theHamilton cohort, 8 of the 57 gastroschisis and 4 of the 28exomphalos mothers had a history of smoking and/or drugabuse. The data for history of smoking and/or drug abusefrom other centers were not available.

The national incidence of gastroschisis and exomphalosaccording to the year is summarized in Figs. 1-3. Thisrepresents an increase of 0.325 per year for gastroschisis and0.22 per year for exomphalos.

The regression equation for gastroschisis is G = 2.2 +0.325(year−1996), P = .018. It means that if the true rate isnot changing, a slope as big as 0.325 would be expected insuch study only 0.018 (1.8%) of the time. The standardresidual deviation is 0.814, and correlation coefficient Rsquare is 57.7%. The regression equation for exomphalos isE = 0.87 + 0.281(year−1996). The residual SD is 0.68 andP value is .043. The correlation coefficient R square is46.7%. Overall, the incidence of gastroschisis has increasedfrom 2.96 in 1996 to 5.16 per 10,000 live births in 2004. Theincidence of exomphalos has also increased from 0.69 in1996 to 3.27 per 10,000 live births in 2004. When theregional data and the national data were plotted in the form ofTrellis plots, the curves were smoother and the degree ofsmoothing was 0.7, which represents an increasing regionaltrend for gastroschisis and exomphalos.

3. Discussion

Several authors have reported an increase in the incidenceof gastroschisis and exomphalos for the last few decades

Fig. 2 National rate of gastroschisis/10,000 live births with Poisson error bars.

553Gastroschisis and exomphalos

(Table 2 A and B). The exact cause of the increasing trend isnot known. The selection bias, increased reporting, increasedprenatal detection by ultrasound, and wrong classificationhave been put forward to explain the global trend but wouldseem to be insufficient to explain the consistency and degreeof increased incidence observed in all series. Zhou et al [15]did not find an increasing trend of gastroschisis in Chinabetween 1996 and 2000. They have reported higherincidence of gastroschisis in the rural population comparedto the urban population.

The incidence of exomphalos has not changed asmarkedly. During 1987 to 1995, it decreased from 1.13 per10,000 to 0.77 in England and Wales [14]. Salihu et al [21]has reported a decreased incidence of exomphalos in the stateof New York during 1992 and 1999 and found that the risk ofexomphalos and gastroschisis was greater in rural popula-

Fig. 3 National rate of exomphalos/10,00

tions. In this study, the incidence of both gastroschisis andexomphalos has increased from 2.96 and 0.69/10,000 livebirths in 1996 to 5.16 and 3.27/10,000 live births in 2004,respectively. These findings are consistent with other studiesthat have shown an overall increase in anterior abdominalwall defects [8-11,13-16,22].

The young maternal age has long been associated withgastroschisis. The cases of gastroschisis are clustered aroundthe young maternal age, whereas the age distribution ofexomphalos is U shaped [21]. The incidence of gastroschisishas been reported highest in mothers less than 20 years old,and there is 5.4 times more risk compared to mothers who are25 to 29 years old [15]. Exomphalos has been reported inolder mothers [20]. In our study, the mean maternal age forgastroschisis and exomphalos was 21 and 26 years,respectively. These findings are parallel with other studies

0 live births with Poisson error bars.

Table 2 Geographical changes in the trend of incidence ofgastroschisis (A) and exomphalos (B) per 10,000 liver births

Country Period Incidence/10,000live births

A.Japan [13] 1975-1997 0.131-0.467Western Australia [6] 1980-1993 0.48-3.16North England [12] 1986-1996 1.48-4.72Hawaii [18] 1986-1997 2.52-3.85SW England [11] 1987-1995 1.6-4.40Norway [7] 1967-1998 0.5-2.9Eastern Ireland [10] 1990-2000 1-4.9North Carolina [8] 1997-2000 2-4.5New Zealand(current study)

1996-2004 2.96-5.16

B.Japan [13] 1975-1997 0.322-0.626United Kingdom(England/Wales) [14]

1987-1995 1.13-0.77

France [19] 1979-1998 2.18Denmark [20] 1979-1989 2.07New Zealand(current study)

1996-2004 0.69-3.27

554 V. Srivastava et al.

that show younger mothers are associated with gastroschisis[8-10,13-16,22] and older mothers are associated withexomphalos [12-14].

Goldkrand et al [23] found equal distribution of gastro-schisis and exomphalos between white and African Americanwomen. Omphalocele has been reported commonly in blackAmerican infants compared to white, and there has been anincrease in the incidence of gastroschisis in Hispanic infants[21]. Although, we have not attempted to study the relation-ship of ethnicity with abdominal wall defects, our observationthat most women with gastroschisis and exomphalos incurrent study were whites despite New Zealand being amulticultural country. This observation warns further study tofind out genetic and sociocultural influences involved in theetiology of abdominal wall defects.

The low socioeconomic status, maternal use of alcohol,cocaine, methamphetamine, and smoking has been asso-ciated with a high risk of gastroschisis in several studies[24-26]. Curry et al suggested smoking as a known risk factorfor abdominal wall defects [27]. Morrison et al [28]concluded that there is 18% incidence of the use of therecreational drugs in mothers with gastroschisis. Althoughthey could not prove that this was caused by usingvasospastic recreational drugs they postulated that this maybe because of the increased incidence of gastroschisis inyoung mothers who were using drugs. We found that only14% of mothers had a history of smoking and drug abuse inthe Hamilton cohort; however, because of the nonavailabilityof similar data from other centers, we were not able toconfirm this in the current study; we suggest that furthernational studies be done to ascertain this possible association.

This retrospective study, which was triggered by animpression of an apparent rise of the number of gastro-schisis infants, has certain limitations such as the unknownnumber of stillbirths and terminations of pregnancy andnonavailability of national or regional perinatal register(s) inNew Zealand.

Our study has shown that in New Zealand the incidence ofgastroschisis and exomphalos appears to be rising, which isconsistent with worldwide trends in showing the increasingincidence of anterior abdominal wall defects.

Acknowledgment

Mr R. Littler, Statistician, University of Waikato,Hamilton, New Zealand, for assistance in preparing thestatistical analysis.

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