The goal of this observational study is to determine the incidence of perioperative cerebral desaturation in neonates undergoing surgery for congenital malformations. The main questions it aims to answer are:

1. The perioperative factors associated with occurrence of cerebral desaturation
2. The association between perioperative cerebral desaturation, perioperative/hospital outcomes, and physiological conditions.

Participants will undergo Near-infrared spectroscopy (NIRS) and electroencephalogram (EEG) monitoring for one hour before surgery, during surgery, and up to 24 hours after surgery.

The NIRS EEG sensors will be placed about an hour before surgery. The recording will start once sensors are placed, continue throughout the duration of surgery, and end 8-24 hours after end of surgery. Sensors will be removed at the end of recording. No additional anesthesia and/or sedation will be required for the preoperative and postoperative recordings. The EEG and NIRS monitors will be blinded to clinical staff. EEG and NIRS monitoring will not prolong anesthesia or the duration of the surgical repair, and should not interfere with routine patient care. NIRS and EEG data will be downloaded from the monitors at the end of recording for analysis.

Medical record review will be conducted at 100 days postop or hospital discharge (whichever is sooner). The information below will be extracted:

• Respiratory record
• Post-op recovery, ICU, and discharge records
• Cardiac and Neurologic records
• Neurologic test such as radiology and lab tests
• Mortality status

Inclusion Criteria:

1. Infants ≤ 60 weeks post-menstrual age on day of surgery.
2. Neonatal surgery for congenital abdominal/gastrointestinal malformations (diaphragmatic hernia, gastroschisis, omphalocele, intestinal atresia, Hirschsprung's disease, imperforate anus, necrotizing enterocolitis), congenital cystic adenomatoid/pulmonary airway malformation (CCAM/CPAM), esophageal/tracheoesophageal fistula (EF/TEF), and spinal malformations (myelomeningocele, sacrococcygeal teratoma).
3. The same patient may be enrolled multiple times for repeat or different procedures that meet the above criteria. These subjects will be counted more than once towards the enrollment goal.
4. Parental/guardian permission.

Exclusion Criteria:

1) Patients with hydrocephalus limiting frontal-parietal brain volume, interventricular hemorrhage (grades 3 or 4), malformation or cerebral infarction of frontal-parietal brain.

Infant subjects ≤ 60 weeks post-menstrual age who are undergoing surgery for congenital malformat