High-Rise Syndrome Associated Stillbirth and Obstructive Dystocia in a Pregnant Rhesus Macaque (Macaca mulatta)

Abstract

Stillbirth in non-human primates represents failure of the maternal–fetal–placental unit and may result from abnormal fetal presentation, maternal compromise, or trauma. In rhesus macaques, mean gestation length is approximately 166 ± 3 days, and normal neonatal birth weight ranges between 450–550 g. The haemochorial placenta makes fetal survival highly dependent on uninterrupted maternal perfusion. Documentation of trauma-associated dystocia in free-ranging rhesus macaques remains limited. An adult pregnant rhesus macaque (Macaca mulatta), weighing approximately 6–7 kg, was rescued following suspected high-rise trauma based on clinical presentation and injury patterns consistent with blunt force impact. The animal presented deeply unconscious in lateral recumbency with respiratory depression, cardiovascular instability, hyperthermia, and abdominal contusions. Rectal temperature ranged from 103–105 °F (39.4–40.5 °C), heart rate was 60–70 beats/min (reference 160–220 beats/min), and respiratory rate was 10–15 breaths/min (reference 30–45 breaths/min), indicating severe systemic compromise. Per-vaginal examination revealed complete cervical dilation with bilateral forelimb flexion, confirming obstructive dystocia secondary to fetal malposture. Emergency stabilization included intravenous Ringer’s lactate (200 mL), dextrose normal saline (100 mL), cardiopulmonary resuscitation (100–120 compressions/min), and corticosteroid therapy. Per-vaginal mutation corrected limb flexion, followed by assisted extraction using obstetrical forceps, resulting in delivery of a dead female fetus. Fetal morphometry showed crown–rump length 160 mm, femur length 49 mm, limb length 145 mm, and head circumference 191 mm, corresponding to approximately 168 days of gestation (near term). Maternal parameters improved following oxytocin (10 IU IM, 5 IU IV) and tranexamic acid (10 mg/kg IV) administration, and hemorrhage was controlled. The findings indicate an association between suspected high-rise trauma, advanced gestation, and obstructive dystocia; however, definitive causality cannot be established without placental or histopathological evaluation. This case emphasizes rapid stabilization and timely obstetrical intervention in trauma-associated reproductive emergencies in urban free-ranging primates. Limitations included unknown timing of injury and absence of hematological or biochemical analysis due to rescue constraints.