Ukrainian Journal Health of Woman. 2026. 3(184): 87-96. doi: 10.15574/HW.2026.3(184).8796
Tkalich V. O.
Bogomolets National Medical University, Kyiv, Ukraine

For citation: Tkalich VO. (2026). Morphofunctional changes of the placenta in preterm birth: histological and immunohistochemical assessment of Ki-67 expression. Ukrainian Journal Health of Woman. 3(184): 87-96. doi: 10.15574/HW.2026.3(184).8796
Article received: Mar 26, 2026. Accepted for publication: Jun 01, 2026.

Preterm birth (PTB) remains an important cause of perinatal morbidity and mortality. The combined study of histological changes and Ki-67 expression allows for clarifying the morphofunctional state of the placenta in premature pregnancy termination.
Aim – to evaluate histological changes and Ki-67 expression in placental structures following in PTB at different gestational ages.
Materials and methods. A total of 200 women delivered at the Kyiv Perinatal Center between 2020 and 2025 were examined. Four groups were formed: group I, 22-27 weeks (n=50); group II, 28-33 weeks (n=50); group III, 34-36⁺⁶ weeks (n=50); and the control group – uncomplicated deliveries at 37-41 weeks (n=50). Histological and immunohistochemical examinations of the placentas were performed with the determination of Ki-67 expression. One-way analysis of variance (ANOVA) or the Kruskal-Wallis test, Pearson’s χ² test or Fisher’s exact test were used; differences were considered statistically significant at p<0.05.
Results. Significant intergroup differences in Ki-67 expression were established (p<0.01–0.001). The highest values in most structures were identified at 28-33 weeks (15.0–35.0%), with a subsequent decrease. The frequency of villous fibrosis (p=0.006) and calcification (p<0.001) increased with advancing gestational age.
Conclusions. Placental morphological changes and cellular proliferative activity depend on gestational age. Decreased Ki-67 expression and an increased frequency of fibrosis and calcification reflect the transition from active remodeling to structural maturation of the placenta. Interpretation of changes in PTB requires taking into account the gestational age.
The study was conducted in accordance with the principles of the Declaration of Helsinki. Written informed consent was obtained from the participants.
The authors declare no conflicts of interest.
Keywords: preterm birth, placenta, histological examination, immunohistochemical examination, Ki-67.

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