Dystocia commonly occurs in guinea pigs mated for the first time after 7 months of age, since at the time of delivery the pubic symphysis is ossified and, therefore, can no longer widen under the effect of relaxin. In this case, a Caesarean section is necessary. Other causes of dystocia are excessively large foetuses (which occurs particularly if there are few foetuses), maternal obesity, abnormal foetal presentation, ketosis and uterine inertia.
Dystocia is said to be present when the guinea pig cannot deliver after 20 minutes of continuous contractions or 2 hours of intermittent contractions.
The degree of widening of the pubic symphysis can be determined by palpation. If it is sufficient (at least 1.5 cm) an X-ray should be performed to determine the size and position of the foetuses. In the case of full-term foetuses without other problems and in the presence of weak uterine contractions, the animal can be given parenteral calcium (100 mg/kg intramuscularly) followed by oxytocin (1-2 units intramuscularly). Foetal expulsion can be facilitated by lubricating the birth canal with lubricating gel or vaseline, instilled with a catheter. If delivery has not occurred within 15 minutes of the administration of oxytocin, a Caesarean section should be performed without further delay since the condition of the parturient deteriorates rapidly. Even if the condition of the sow appears very poor, the operation can be attempted to save the young animals, which have a good chance of survival.