Differential Pregnancy Decisions in a Woman With a Recurrent Prenatal Diagnosis of Hypophosphatasia

Hypophosphatasia (HPP) is a rare inherited bone disorder caused by ALPL gene mutations, leading to reduced alkaline phosphatase (ALP) activity and impaired bone mineralization. Although its prevalence is relatively higher in Japan, prenatal diagnosis remains challenging. In particular, obstetricians and clinical geneticists, who are typically involved in prenatal assessment, often have limited experience with this condition due to its rarity. Among the various types of HPP, the prenatal benign form has a favorable prognosis, yet awareness and understanding of this specific subtype are limited. We report a case involving two separate pregnancies in the same woman, both diagnosed prenatally with HPP. During the second pregnancy, counseling was provided at 21 weeks by a physician. Given the rarity of HPP, even specialists such as obstetricians, pediatricians, or clinical geneticists often have limited direct clinical experience with the condition. Consequently, the counseling leaned toward a negative outlook, and the patient opted for termination. In contrast, during the third pregnancy, counseling began at nine weeks with detailed and balanced information, informed by the previous case and supported by a multidisciplinary team. This time, the patient elected to continue the pregnancy. The neonate was diagnosed with prenatal benign HPP and showed favorable clinical progress. This case highlights how the timing, quality, and balance of prenatal counseling can significantly influence parental decision-making in pregnancies complicated by rare diseases. In cases of rare conditions such as HPP, early and accurate counseling by an experienced multidisciplinary team is essential to support informed and autonomous decisions.