With the authorization of the local institutional review board (R-2012-6790-89), the study was
conducted in Hospital General of Zona 2 A Troncoso, from the Instituto
Mexicano del Seguro Social (IMSS), and comprised the following phases:
a) Identification of possible predictive outcome measures: From January
2005 to December 2010, a cohort was prospectively defined including newborn infants of any gestational age,
both genders, multiple gestations and visible external malformations. They had to be delivered at the Obstetrical-Surgery Unit of the Hospital, admitted at the NICU on their first day of life and under care until discharged for any cause. Patients born in other units were excluded and newborn infants voluntarily withdrawn by their parents or transferred to
other hospitals were removed. The sample size calculation was based on the previous year
statistics, with a total of 3450 births and 11% mortality, a= 95% and d= 99% (0.001), replaced
in the odds ratio formula for finite population,9 with an estimate patient number of 204. A 10% was added to make up for estimated losses, resulting in a final calculation of 224 patients