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Primary uterine inertia
Synonym(s): Primary maternal dystocia
Introduction
- Primary uterine inertia is defined as the failure of the myometrium to ever establish a contractile pattern adequate to expel neonates from the uterus.
- Cause: unknown. There could be a genetic predisposition to primary inertia, as it has been documented in related bitches.
- Less common than secondary uterine inertia which has several etiologies Dystocia.
- Signs: stage 1 labor is not initiated, even after the due dates have passed.
- Diagnosis: primary uterine inertia can only be confirmed using tocodynamometry (uterine monitoring).
- Treatment: caesarean section.
- Prognosis: good if timely diagnosis and intervention.
Presenting signs
- Confirmed pregnant bitch at or past term showing no signs of impending parturition (labor).
- At term, the bitch is normal otherwise, with lactation present, a relaxed perineum and vulva. The body temperature may have dropped to <99°F (37.22°).
- Fetal death can occur after term gestation; the bitch can become toxic from intrauterine fetal death with time.
Cost considerations
- Moderate for elective, non-emergency Caesarean section Caesarean section; higher for emergency Caesarean section with complications (fetal stress, fetal death, decomposing fetuses, bitch compromise).
Special risks
- Incorrect calculation of a pregnant bitch's due dates (correct gestation length) can cause a misdiagnosis Estrus and gestation periods.
- Gestation in the bitch is 64-66 days from the LH surge, or from the initial rise in progesterone asociated with the LH surge.
- Calculating gestation period from the time of last breeding (mating) is not precise as normal gestation can be 58-72 days from a breeding. Bitches may breed before their window of fertility, and semen can live for up to 7 days in the female reproductive tract.
- Alternatively, if vaginal cytology was the only form of ovulation timing performed Ovulation detection, normal gestation is 56-58 days from the first day of cytologic diestrus (<50% of the cells are superficial).
- Alternate, but less precise methods of gestationing aging include ultrasound (organogenesis and gestational sac diameter, biparietal, and crown-rump measurements) and radiography (presence of fetal dentition) Pregnancy: diagnosis.
Pathogenesis
Etiology
- Failure of the myometrium to ever establish a contractile pattern adequate to expel neonates from the uterus.
- The cause of this failure has not been discovered.
Predisposing factors
- History of a previous apparent lack of labor is suggestive.
Pathophysiology
- Serial tocodynamometry finds no evidence of developing uterine contractile patterns that will produce a vaginal delivery.
Timecourse
- Critical that the diagnosis is made before fetal compromise occurs.
- Breeders tend to present bitches 2-3 days after their believed due date has passed.
Diagnosis
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Treatment
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Prevention
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Outcomes
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