Purpose: It is challenging to predict fetal macrosomia before delivery. This study aimed at assessing predictors of fetal macrosomia at Iringa Regional Referral hospital in Tanzania from June to December 2020. Method: An unmatched case-control study with 216 participants of whom 72 were cases - women who delivered babies weighing ? 4000g - and 144 were controls - women who delivered babies weighing 2500g to 3499g. Purposive sampling technique described below was employed to recruit both controls and cases. SPSS version 25 software program was used for data entry and analysis. Results: Of the 216 participants, 116 (53.7%) were aged between 25 – 34 years and standard deviation of 6.0. Majority 132 (61.1%) delivered at a gestational age of 37 – 39 weeks + 6 days of which 17 (23.6%) were cases and 115 (79.86%) were controls. The predictors of fetal macrosomia were advanced gestation age (AOR=8.10, 95% CI 3.66-17.91, p=<0.0001) and diabetes mellitus during pregnancy (AOR =14.94, 95% CI 1.60 -39.91, p= 0.0178). Conclusion: Women with higher gestational age and gestational diabetes mellitus are at an increased risk of delivering a macrosomia baby at Iringa Regional Referral hospital. Community prevention of obesity and an early delivery management plan will help to prevent the occurrence of adverse outcomes.

Keywords: Macrosomia, Predictors, Tanzania