Uterine Inertia

Uterine inertia refers to a situation in which the muscular contractions of the uterus during labour become weak, infrequent, or stop altogether, preventing the normal progression of birth. This can occur at the start of labour (primary inertia) or after one or more puppies or kittens have been delivered (secondary inertia). The underlying causes vary and may include exhaustion of the uterine muscle, low calcium or glucose levels, mechanical obstruction, or insufficient hormonal signals. Owners most often notice that labour has started but then stalls—contractions may seem absent or ineffective, and no puppy or kitten appears despite straining, or there may be long gaps between births with signs of maternal distress or exhaustion. In some cases, labour never begins at all despite the pregnancy reaching or passing the expected due date. This page explores the signals that may point towards uterine inertia, the metabolic and mechanical factors that can contribute, the investigations used to assess the situation, and the range of approaches that may be considered depending on the individual circumstances.