Ratio of the number of β-cell clusters relative to islets (A), the proportion of β-cells present in clusters relative to the total population of β-cells (B), the percentage of total β-cells undergoing DNA synthesis (Ki67+) (C) and when separated into β-cells located in either islets (D) or clusters (E) in mouse pancreas between gestational days (GD) 6 and 18, and at postnatal day 7. During pregnancy, the Ins+ cell population in β-cell clusters showed a greater proportional increase than in islets. The number of proliferating β-cells was greatest at GD12 and proliferating cells were located both in clusters and in islets. One-way ANOVA with Tukey’s post-hoc test, * p < 0.05, ** p < 0.01, ***p < 0.001 vs. control; † p<0.05, †† p<0.01 vs. GD 12 (n = 4 per time point).