Dystocia
Introduction
Dystocia refers to abnormal or difficult birth. Causes include maternal factors such as uterine inertia and inadequate size of the birth canal and/or foetal factors such as foetal oversize or abnormal orientation.
Other factors influencing dystocia include: breed, age, parity, body condition, environment, nutritional status and energy balance.
Parturition is divided into three stages:
- Stage 1: this is the preparatory stage, starting at the onset of regular uterine contractions followed by cervical dilatation and the foetus assuming the correct disposition for passage through the birth canal.
- Stage 2: the expulsive stage, characterised by the onset of abdominal contractions which together with uterine contractions lead to foetal expulsion
- Stage 3: separation and expulsion of the foetal membranes. In polycotous species second and third stages are often inter-mixed.
Incidence of Dystocia
Figure of incidence are often unreliable as the assessment of dystocia is highly subjective.
Average figures are:
Cow: 3-4% in dairy cows, much higher in some beef breeds
Mare: 1-2% of ponies, up to 10% in some draught breeds
Ewe: 2-3%, can reach 30% in some flocks
Sow: <1%
Bitch: Can be 100% in some brachycephalic/achondroplastic breeds
Queen: Low in feral animals, high in brachycephalics
Common Causes
Maternal factors tend to be more important in polycotous species, and foetal factors tend to be more important in monocotous species.
Cow: foetomaternal disproportion is common in heifers and beef breeds. Faulty disposition is also important
Mare: faulty disposition, especially postural abnormalities. Foetomaternal disproportion is rare.
Ewe: faulty disposition and twin presentations are the most frequent but are readily dealt with by the shepherd. Foetomaternal disproportion and ring womb are also common.
Sow: uterine inertia, foetomaternal disproportion in gilts and simultaneous presentations occur rarely.
Bitch: uterine inertia, foetomaternal disproportion, especially in brachycephalic breeds as well as other breeds with small litters.
Queen: similar to the dog, foetomaternal disproportion is more common with smaller litters.
Clinical approach to dystocia in small animals
A thorough history regarding breeding dates and previous whelping history is desirable.
Physical examination should look for signs of systemic illness that, if present, may necessitate immediate cesarean section. The normal vaginal discharge at parturition is a dark green colour; abnormal colour or character warrants immediate attention. A dark green/black vaginal discharge associated with a lack of signs of parturition may indicate premature placental separation.
A digital vaginal examination should be performed to evaluate patency of the birth canal and the position and presentation of the fetus(es). Radiography or ultrasonography can determine the presence and number of fetuses, as well as their size, position, and viability.
Manipulation can be attempted in the case of reducible malpresentations or a dead foetus. This involves using digital manipulation sometimes combined with transabdominal manipulation to stabilise the foetus.
Medical management may be considered when the condition of the dam and fetuses is stable, when there is proper fetal position and presentation, and when there is no obstruction. Oxytocin given IM up to 3 times at 30-min intervals, with or without 10% calcium gluconate given slowly IV in an attempt to promote uterine contractions. If no response follows, a cesarean section should be performed.
Caesarean section is indicated for obstructive dystocia, dystocia accompanied by shock or systemic illness, primary uterine inertia, prolonged active labor, or if medical management has failed.
Clinical approach to dystocia in large animals
A thorough history should establish the length of gestation, parity, and problems seen during pregnancy. Also find out when the animal started straining and if any water or fluid bags have appeared.
It is also important to establish what has been done so far by the farmer or owner including any drugs administered.
Physical examination of the dam who might have systemic illness, such as milk fever in cows. Proper restraint and assistance should be sought, and initial treatment may include fluid therapy, pain relief and the provision of calcium.
Position of the dam: sows should be lying, cows and mares should be standing and ewes can stand or lie.
Vaginal examination: the vulva, vagina and cervix should be assessed for dilation, torsion or injury. Copious lubrication should be used at all stages of the examination.
Foetal assessment should establish its presentation, posture and position and identify any palpable structures. Foetal viability can be assessed by feeling pulses on the limbs or tongue.
Anaesthesia is not essential, but an epidural can be administered to help reduce straining.
Manual correction of dystocia: relies on traction to facilitate expulsion, repulsion of the foetus back into the uterine lumen to enable further manipulation, and extension of the foetal extremities.
Ropes can be applied to both legs and the head and traction applied whilst manually dilating the vagine and vulva.
If the foetus is too large to be delivered vaginally, a caesarean operation or a foetotomy should be performed.
Prevention: many causes of dystocia in large animals can be prevented, especially in cows. Foetomaternal disproportion can be prevented by ensuring that heifers are well-grown, with a normal pelvic conformation, and sires should be selected for ease of calving.
Postpartum complications
Dystocia leads to an increased incidence of stillbirths, foetal rejection by the dam, increased neonatal mortality and morbidity, increased incidence of mortality in the dam, reduced dam productivity and fertility, increased incidence of sterility, puerperal disease and culling.
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Cattle Medicine Q&A 10 |
References
Kahn, C. (2005) The Merck Veterinary Manual 9th Edition Merck and Co
von Heimendahl, A. Cariou, M. (2009) Normal parturition and management of dystocia in dogs and cats In Practice 31:254-261
Frame, N. (2006) Management of dystocia in cattle In Practice 28:470-476
McGladdery, A. (2001) Dystocia and postpratum complications in the mare In Practice 23:74-80