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Objective Diabetes during pregnancy causes an intrauterine environment that influences lifetime sickness of the mother and the fetus. There is a correlation between diabetes and telomere shortening; however, very little is known about telomere homeostasis in the placenta. We aimed to study the telomerase complex in placentas and in cord blood leukocytes from patients with poorly controlled diabetes. Methods Biopsies from 16 third-trimester placentas and cord blood samples from pregnancies complicated with uncontrolled diabetes and from 16 gestational age-matched controls from uncomplicated pregnancies were examined. The expression of hTERT (human telomerase reverse transcriptase) was evaluated by immunohistochemistry and by RT-RCR. TERC gene copy number and telomere capture were evaluated by FISH. Results Telomerase expression was significantly lower in the diabetic placentas, both the protein (17.8 ± 2.8% cellular staining vs. 37 ± 5.32%, P = 0.012) and the mRNA levels (0.42 ± 0.03 folds, P = 0.022). Lower expression of TERC gene copy number were shown in the diabetic placentas compared to the healthy controls (1.7 ± 0.8% vs. 3.7 ± 1.6%, P = 0.035). We also detected higher percentage of cells with telomere capture among the diabetic trophoblasts compared to the healthy controls (19.8 ± 5.12% vs. 9.6 ± 3.65%, P = 0.038). Those differences were not observed in cord blood leukocytes from the same samples. Conclusions Uncontrolled diabetes during pregnancy disrupts telomere-telomerase homeostasis in the trophoblasts. These changes may increase the risk for metabolic diseases in adulthood among offspring of pregnancies complicated by gestational diabetes mellitus as part of intrauterine programming. These variations were not observed in cord blood leukocytes, which imply different telomere homeostasis mechanisms in fetal cord blood.