Background and objectives: Diabetes in pregnancy can lead to severe neonatal and maternal adverse events. Moreover, there is an increase in GDM prevalence. Therefore, we aimed to compare insulin detemir (IDet) with the neutral protamine Hagedorn (NPH) in diabetic pregnant women. Methods: We searched four electronic databases until August 2021: PubMed, Scopus, Web of Science, and Cochrane. We included randomized controlled studies that compared IDet with NPH in diabetic pregnant women. We extracted both maternal and neonatal outcomes, and used RevMan software to conduct the analysis. Results: A number of five studies were included. The analysis showed a significantly lower risk of hypoglycemic events during pregnancy in the IDet group than the NPH group [RR=0.6, 95% CI [0.43, 0.84], p=0.003], and a higher gestational age (GA) at delivery in the IDet group than the NPH group [MD= 0.28, 95% [0.02, 0.55], p=0.03]. On the other hand, the analysis revealed non-significant differences between IDet and NPH in terms of birth weight, congenital anomalies, neonatal hypoglycemia, preterm delivery, and others. Conclusion: Insulin detemir (IDet) was preferred over neutral protamine Hagedorn (NPH) in terms of showing lower rates of hypoglycemic events during pregnancy and a higher gestational age at delivery. Meanwhile, there were non-significant variations between them when it comes to neonatal outcomes, such as weight at birth, congenital anomalies, or neonatal hypoglycemia.