Gastroschisis and Mode of Delivery: National Trends and Evaluation of Outcomes, 1991 to 2005

1. Gastroschisis and Mode of Delivery: National Trends and Evaluation of Outcomes, 1991 to 2005 T. Mac Bird University of Arkansas for Medical Sciences College of Medicine, Department of Pediatrics College of Public Health, Department of Health Policy and Management

2. Background • Gastroschisis is a severe birth defect where the intestines are herniated through the abdominal wall and exposed directly to amniotic fluid • Affects 1 in 2500 live births • Rates of Gastroschisis have been reported to be rising in both in the US and in other nations around the world

3. Background • No consensus on preferred mode of delivery for infants with gastroschisis. • Proponents of delivery by c-section argue • Reduced risk of infection • Reduces damage to eviscerated intestines • Allows scheduling of neonatal care team • However, no evidence of improved outcome over vaginal delivery

4. Objectives • Use national hospital discharge data to determine trends in CS for infants with gastroschisis • Use instrumental variable methods to approximate the results of a randomized controlled trial using observational data • Determine if outcomes for infants with gastroschisis differ by mode of delivery

5. Database • Nationwide Inpatient Sample (NIS) • Created by the Agency for Healthcare Research and Quality • Approximates a 20% stratified random sample of all community hospital in the US • ~ 8 million discharges per year • Kid’s Inpatient Database (KID) • Pediatric specific • Larger pediatric sample for available years

6. Subjects • Live births in NIS/KID between 1991 and 2005 • Diagnosis code for abdominal wall defect (ICD-9-CM 765.7) • Procedure code for gastroschisis repair (ICD-9-CM 54.71) • Singleton birth • Received surgical repair in birth hospital

7. Analysis • Bivariate probit models with instrumental variables • Dependent Variables – Mortality, necrotizing enterocolitis, sepsis, respiratory distress, transitory tachypnea, intestinal surgery, medical complications, staged closure • Independent Variable – Mode of delivery, c-section = 1, vaginal delivery = 0

8. Analysis • Instrumental Variables – Admission to hospital on a weekend, c-section rates for infants with gastroschisis by US regional division per year • Control Variables – basic demographics, hospital characteristics, 10 indicators for comorbid birth defect categories, mechanical ventilation, fetal distress, maternal complications, small for gestational age, 4 birth weight categories

9. Results • 2,785 (10,073 weighted) cases of gastroschisis • 1,498 (5,332 weighted) or 52.9% born by c-section • 1,497 (5,293 weighted) or 52.6% were born preterm • Rates increased from low of 1.7/10,000 live births in 1996 to a high of 4.4/10,000 in 2005

10. Results

11. Results

12. Conclusions • Rates of gastroschisis have increased steadily over the past 15 years in the United States • This study found no benefit to delivery of infants with gastroschisis by c-section compared to vaginal birth • Delivery of infants with gastroschisis by c-section could be harmful

13. Limitations • Discharge data created for reimbursement • Coding practices can vary by hospital, state, region, and over time • The more severe/expensive a diagnosis or procedure the more likely to be coded • No code for gastroschisis • Algorithm likely under codes gastroschisis slightly although positive predictive value should be high

14. Evan Kokoska Chenghui Li Mario Cleves Nirvana Manning Mick Tilford James Robbins Charlotte Hobbs Acknowledgements This study was funded in part by a grant from the Arkansas Biosciences Institute