Placental Pathological Findings and Clinical Outcomes in Triplet Pregnancies Conceived via Oocyte Donation and Non-Oocyte Donation: A Case–Control Study

<b>Objective</b>: This study aimed to assess whether oocyte donation in triplet pregnancies is associated with increased risk of placental abnormalities and pregnancy complications compared to triplet pregnancies conceived through assisted reproductive technology (ART) without oocyte donation. <b>Methods</b>: This single-center, retrospective, case-control study analyzed triplet pregnancies conceived via ART. The case group included pregnancies resulting from oocyte donation, while the control group comprised triplet pregnancies conceived by ART without oocyte donation. Maternal, obstetric, fetal, and neonatal outcomes were assessed. Gross and histopathological placental findings were evaluated using standardized criteria. Univariate and multivariate statistical analyses were performed. <b>Results</b>: A total of 77 triplet pregnancies (231 fetuses) were included: 29 in the oocyte donation group (87 fetuses) and 48 in the non-oocyte donation group (144 fetuses). Multivariate analysis revealed significantly higher rates of pregnancy-induced hypertension (<i>p</i> = 0.03), preeclampsia (<i>p</i> = 0.03), fetal growth restriction (<i>p</i> = 0.04), and fetal death (<i>p</i> = 0.01) in the oocyte donation group. Placental evaluation showed a higher frequency of infarcts (<i>p</i> = 0.04) and chronic inflammatory lesions-chronic villitis (<i>p</i> = 0.02) and chronic deciduitis (<i>p</i> = 0.03)-as well as signs of fetal vascular malperfusion, including avascular villi (<i>p</i> = 0.02) and stromal-vascular karyorrhexis (<i>p</i> = 0.01). Intervillous fibrin deposition was also more common in this group (<i>p</i> = 0.02). <b>Conclusions</b>: Oocyte donation in triplet pregnancies is associated with increased rates of placental abnormalities and adverse maternal and fetal outcomes when compared with ART without oocyte donation. Placental examination may provide valuable insights into the mechanisms involved. Further research is warranted to clarify the underlying immunological and vascular pathways. <b>Synopsis</b>: In our cohort of 77 triplet pregnancies, those conceived via oocyte donation showed significantly higher rates of preeclampsia, fetal growth restriction, and fetal death. Placental examination revealed more chronic villitis, deciduitis, intervillous fibrin, avascular villi, and stromal-vascular karyorrhexis, suggesting immune and vascular dysfunction in oocyte donation pregnancies.