Aim: Antenatal corticosteroids (ACS) are recommended for use in antenatal mothers at risk of preterm delivery before 34 weeks. One common side effect is the propensity to cause hyperglycemia. Our study aimed at characterizing glycemic response to betamethasone in preterm women and compared this response in patients with gestational diabetes mellitus (GDM) and those without GDM. Materials and methods: After ethical clearance, 160 preterm antenatal patients who required ACS were included between 28-and 34-week periods of gestation. They were allotted into two groups: those with GDM and those without GDM. Fasting blood sugar (FBS) and postprandial blood sugar (PPBS) were followed for 4 days after betamethasone administration. Results: A total of 54.65% showed an elevated FBS in the normal group on D2 and this reduced to 29.53% on D4 and 19.76% on D5. Similarly, PPBS was elevated in 54.65% on D2 and reduced to 26.7% on D4 and 13.95% on D5, whereas in the GDM group, FBS remained elevated on D2-D4 in 77.02, 81.08, and 71.62%, respectively, and started showing a downward trend with 45.94% on D5. Similarly, PPBS was elevated in 78.38, 77.03, and 67.57% on D2-D4, respectively, and reduced slightly to 56.76% on D5. Conclusion: Our findings highlight the need for monitoring the glycemic levels even up to 5 days after ACS administration. Clinical significance: With the increasing prevalence of GDM in antenatal mothers in India, this study highlights the need for more stringent glucose monitoring after steroid administration and also the need for protocols on the frequency of monitoring and dosage of insulin regimen.