Inclusion and exclusion criteria
The selected studies used for this meta-analysis had to match the following criteria:
(1) All infants born after <32 weeks of gestation and birth weight < 1500g; (2) Randomized controlled studies; (3) A group exposed to prophylactic caffeine citrate therapy (0-3 days of life), a control group of infants not receiving caffeine until they develop AOP, and a comparison between the two groups; (4) At least one of the parameters was included in the outcome measures: The primary outcomes of interest were apnea of prematurity (AOP), duration of mechanical ventilator(days) and duration of oxygen therapy(h); Secondary outcomes included: biparietal diameter (BPD), patent ductus arteriosus (PDA), retinopathy of prematurity (ROP), necrotizing enterocolitis (NEC), intra-ventricular hemorrhage (IVH) and death before hospital discharge. All diseases diagnosis relied on the recording of patient charts or surgical data.
Any study that met a specific exclusion criterion was removed from the meta-analysis:
Case reports, reviews, or animal trials; (2) The studies with unclear or inadequate exposure/outcome definitions; and (3) The studies with insufficient information for extraction data.