Congenital pulmonary hypoplasia is a devastating condition affecting fetal and newborn pulmonary physiology, resulting in great morbidity and mortality. The fetal lung develops in a fluid-filled environment. In this work, we describe a novel, implantable pressure sensing and recording device which we use to study the pressures present in the fetal pulmonary tree throughout gestation. The system achieves 0.18 cm H2O resolution and can record for twenty one days continuously at 256 Hz. Sample tracings of in vivo fetal lamb recordings are shown.