5th International Conference on Gynecology and Obstetrics

Leidy Salazar is a third-year resident in Obstetrics and Gynecology at the Military Hospital. She has developed a strong interest in comprehensive women's healthcare, particularly maternal and fetal health. Throughout her medical training and residency, she has strengthened her medical knowledge, clinical expertise, and surgical skills while cultivating a strong sense of commitment, responsibility, and empathy in caring for her patients.

Background: Hypophosphatasia is a hereditary bone dysplasia caused by mutations in the ALPL gene that impair bone mineralization. Its prenatal presentation is uncommon and is associated with ultrasound findings that may overlap with those of other lethal bone dysplasias, complicating prenatal diagnosis.

Objectives: The objective is to describe the prenatal diagnostic findings of a case of prenatal hypophosphatasia confirmed in the postnatal period.

Methods: Clinical case report. A 37-year-old primigravida at 20 weeks' gestation was referred for a detailed anatomical ultrasound due to suspected fetal skeletal dysplasia. Prenatal evaluation included serial obstetric ultrasounds, an echocardiogram, and fetal neurosonography to characterize structures and monitor fetal well-being until the end of the pregnancy. A diagnostic amniocentesis was performed for G-banded karyotyping of the amniotic fluid. After birth, the newborn underwent a multidisciplinary assessment, radiological and laboratory studies, and genetic testing using a next-generation sequencing panel for skeletal dysplasias.

Results: Prenatal assessment starting at 20 weeks revealed severe micromelia, with shortening and angulation of the long bones, as well as a small thorax and a cardiothoracic ratio greater than 0.6—findings suggestive of lethal skeletal dysplasia. The prenatal karyotype was normal, and the pregnancy ended at term via Cesarean section, resulting in a live-born female infant with shortened limbs. Postnatal radiological studies showed reduced bone density and metaphyseal and epiphyseal abnormalities, alongside low alkaline phosphatase levels. Finally, genetic analysis identified the homozygous pathogenic mutation c.892G>A p.(Glu298Lys) in the *ALPL* gene, confirming the diagnosis of perinatal hypophosphatasia.

Conclusion: Prenatal hypophosphatasia is a rare skeletal dysplasia; diagnosing it during pregnancy is challenging due to phenotypic variability and the overlap of ultrasound findings with other lethal skeletal dysplasias. This case highlights the importance of serial ultrasound monitoring and a comprehensive approach within maternal-fetal medicine units, which facilitate accurate prognostic assessment, prenatal counseling, and perinatal management planning.