Partial molar pregnancies (incidence: 0.6–2.9 per 1000 pregnancies) are typically associated with triploidies (69,XXX/XXY). Their coexistence with a viable euploid fetus (46,XX/XY) is extremely rare.

We present the case of a 35-year-old woman with a history of bilateral tubal occlusion (2011) who underwent in vitro fertilization (IVF) with preimplantation genetic testing for aneuploidy (PGT-A). Two euploid embryos (46XX and 46XY) were transferred following ovarian stimulation with menotropins 300 IU, dydrogesterone (to prevent an LH surge), and choriogonadotropin alfa.

The first trimester proceeded without abnormalities (CRL: 78 mm). At 19.3 weeks, ultrasound revealed:

1. Bilateral ovarian cysts (1500 cc)
2. Cystic placentomegaly
3. Biochemical findings: elevated hCG (550,362 mIU/mL) and suppressed TSH (<0.005 μUI/mL)

The differential diagnosis included placental mesenchymal dysplasia versus partial hydatidiform mole. Treatment with acetylsalicylic acid, enoxaparin, and vaginal progesterone was initiated. The pregnancy concluded at 33.6 weeks due to premature rupture of membranes, resulting in a live newborn (1850 g, APGAR 8/9, male). Pathological examination confirmed a partial hydatidiform mole in a monochorionic monoamniotic placenta.

Conclusion: This case challenges the classical paradigm by demonstrating a partial molar pregnancy with a viable euploid fetus following IVF, despite PGT-A. It highlights the need for close monitoring in the presence of atypical findings (placentomegaly, elevated hCG) and the importance of updating management protocols in assisted reproduction.

Braulio Cesar Zapien Terrones graduated as a Surgeon from the University of Guanajuato, Mexico, in 2018 and completed his specialization in gynecology and obstetrics in Leon, Guanajuato, in 2024. He successfully published his first scientific paper, titled "Prenatal Diagnosis of Placenta Accreta by Ultrasound and Its Histopathological Association," in the medical journal of the Mexican Institute of Social Security. He is currently in his final year of the subspecialty in human reproductive biology at the Centro Medico Nacional La Raza in Mexico City.