Primary hyperparathyroidism (PHP) during pregnancy is a very rare event that increases maternal and perinatal morbidity and mortality. We present a case in which hypocalcemic tetany of the neonatal infant - caused by transient hypoparathyroidism in the child - finally revealed asymptomatic maternal PHP. An apparently healthy 30-year-old woman had an uneventful pregnancy and delivery. On the 15th postpartal day, the newborn developed hypocalcemic tetany. After receiving supplementation of calcium and vitamin D, the child developed without further pathological findings. Laboratory and radiological studies in the mother led to a diagnosis of maternal PHP. An adenoma of the right lower parathyroid gland was subsequently removed. The search for the cause of hypocalcemia in a newborn should not focus on the patient alone. Examining the apparently healthy mother and approaching the case in a multidisciplinary fashion may benefit both the child and the mother.