BACKGROUND: Congenital and nosocomial infections are important causes of neonatal morbidity and mortality. Maternal transport of immunoglobulins to the fetus mainly occurs after 32 weeks gestation and endogenous synthesis does not begin until several months after birth. Administration of intravenous immunoglobulin provides IgG that can bind to cell surface receptors, provide opsonic activity, activate complement, promote antibody dependent cytotoxicity, and improve neutrophilic chemo luminescence. Theoretically infectious morbidity and morbidity could be reduced by the administration of intravenous immunoglobulin. OBJECTIVES: To assess the effectiveness of intravenous immunoglobulin (IVIG) to reduce mortality/morbidity caused by suspected infection in newborn infants. In secondary analyses to assess the effectiveness of IVIG to reduce mortality/morbidity in those neonates who entered into the studies with suspected infection and who later were confirmed as being infected. SEARCH STRATEGY: MEDLINE, EMBASE and the Cochrane Library were searched in February 2001 using the following keywords: immunoglobulin and infant-newborn, and random allocation, or controlled trial, or randomized controlled trial (RCT). The reference lists of identified RCTs, meta-analyses and personal files were searched. No language restrictions were applied. Unpublished information was requested from and obtained from five researchers (~~ Erdem 1993; ~~ Gokalp 1994; ~~ Haque 1988; ~~ M-Ramirez 1992; ~~ Shenoi 1999~~). SELECTION CRITERIA: The criteria used to select studies for inclusion were: 1) DESIGN: RCT (including quasi-randomized trials) 2) Newborn infants (< 28 days old) 3) INTERVENTION: IVIG for treatment of suspected (and in some infants subsequently proved) bacterial/fungal infection compared to placebo or no intervention. 4) At least one of the following outcomes was reported: mortality during initial hospital stay; length of hospital stay; side effects; psychomotor development/growth at follow up. DATA COLLECTION AND ANALYSIS: Two reviewers independently abstracted information for the outcomes of interest and one researcher (AO) checked for any discrepancies and pooled the results. Typical Relative Risk (RR) and Risk Difference (RD) with 95% confidence intervals (CI) using the fixed effects model are reported for dichotomous outcomes and weighted mean difference (WMD) for continuous data. NNT was calculated for outcomes that showed a statistically significant reduction in RD. MAIN RESULTS: Five hundred twenty nine neonates with suspected infection have been enrolled in RCTs to evaluate the effect of IVIG on neonatal outcomes. These studies were undertaken in seven countries. Six studies (n = 318) reported on the outcomes of randomized patients with clinically suspected infection. The results showed a reduction in mortality following IVIG treatment [typical RR 0.63 (95% CI; 0.40, 1.00), RD -0.09 (95% CI; 0.00, -0.17) of borderline statistical significance. Treatment with IVIG (seven trials, n = 262) in cases of subsequently proved infection did result in a statistically significant reduction in mortality [typical RR 0.55 (95% CI; 0.31, 0.98; RD -0.09 (95% CI; -0.01, -0.18); NNT 11 (95% CI; 5.6, 100]. In spite of different geographical locations of the studies, differences in the mortality in the control groups (range 0% - 43.8%), the use of different IVIG preparations, and different dosing regimens, there was no statistically significant between-study heterogeneity for the outcome of mortality in the two analyses. REVIEWER'S CONCLUSIONS: There is insufficient evidence to support the routine administration of IVIG preparations investigated to date to prevent mortality in infants with suspected or subsequently proved neonatal infection. Researchers should be encouraged to undertake well-designed trials to confirm or refute the effectiveness of IVIG to reduce adverse outcomes in neonates with suspected infection.