The primary objective of this study is to describe the pattern of renal tissue oxygen saturation (SrSO2) using near-infrared spectroscopy (NIRS) in premature infants <30 weeks gestational age. The secondary objective of this study is to evaluate prenatal and postnatal risk factors for acute kidney injury (AKI) in premature infants <30 weeks gestational age. The investigators will also compare various rates of complications including death, length-of-stay, and prolonged duration of mechanical ventilation, among others.

Inclusion Criteria:

• Any neonate less than 30 weeks in gestational age
• Willingness and capacity of both adult parents/guardians to sign consent

Exclusion Criteria:

• An infant with known congenital anomalies of the kidney (i.e., grade 4 or 5 vesicoureteral reflux (VUR), posterior urethral valves, moderate or severe hydronephrosis, autosomal recessive polycystic kidney disease (ARPKD), bilateral renal agenesis or dysplasia)
• Age >30 weeks gestational age
• Age <24 weeks and <500 grams (will be excluded due to sensitivity of skin in this vulnerable population).
• Clinician's decision that NIRS is not suitable due to the patient's clinical condition

The de-identified participant data from the final research dataset will be shared upon reasonable request beginning 9 to 36 months after publication or as required by a condition of awards or supporting agreements, provided the requesting investigator executes a data use agreement with NYU Langone Health. This instance of data sharing will also require separate IRB review as well as review from NYU Langone's Data Sharing Strategy Board (DSSB). Requests should be directed to: Jordan.nelson@nyulangone.org. The protocol and statistical analysis plan will be posted on Clinicaltrials.gov only as required by federal regulation or supporting awards and agreements.

Beginning 9 months and ending 36 months following article publication or as required by a condition of awards and agreements supporting the research.

The investigator who proposed to use the data will be granted access upon reasonable request. Requests should be directed to Jordan.nelson@nyulangone.org. To gain access, data requestors will need to sign a data access agreement. This instance of data sharing will also require separate IRB review as well as review from NYU Langone's DSSB.