Case information:
You are presented with a 4 year old intact female Scottish terrier who the owner believes to be in dystocia. The bitch was bred one time, with chilled extended semen, 61 days ago; serum progesterone concentration was 6.6 ng/ml 63 days ago. She has refused all food for over 24 hours and passed green vulvar discharge 1 hour ago. The owner, an experienced breeder, has seen no coordinated abdominal contractions.
On physical examination, the pulse and respiratory rate are within normal limits. Rectal temperature is elevated, at 103 degrees F. The bitch is not dehydrated and has a normal attitude. No abnormalities are evident on digital vaginal examination. An abdominal radiograph is below.
Question:
Of the information available to you, what may be indicative of an abnormality of parturition in this bitch?
Answer:
Gestation length is normal, at 63 days from ovulation. The information presented here does not allow one to say when Stage I labor may have begun. However, passage of green discharge prior to passage of pups indicates probable placental separation of at least one pup. The four pups visible show no evidence of fetal death (gas within or around the fetuses, collapse of the skull or axial skeleton), appear uniform in size and mineralization, and do not appear to be too big to pass through the pelvis. While it can be normal in bitches for pups to pass caudally (rear limbs and tail presenting to the pelvic canal), remember that it is the pressure of the pup against the internal cervical os that stimulates release of oxytocin and coordinated uterine contractions. It may be that the presentation of the first pup's pelvis and rear limbs is not sufficient to cause oxytocin release. The high rectal temperature is abnormal and may be indicative of hypocalcemia.
Question:
What diagnostics would you like to do now?
Answer:
- Measurement of total or ionized calcium in blood
- Abdominal ultrasound to assess fetal heart rate; consistent decline in heart rate to less than 150-170 beats per minute is indicative of fetal distress
Case Outcome:
Ionized calcium was normal. Abdominal ultrasound revealed heart rates about twice that of the bitch in all four pups. The bitch was treated with 0.5 IU oxytocin IM. No contractions were noted. Use of an instrument such as WhelpWise, which can be used to identify whether or not uterine contractions are occurring, may be beneficial in cases such as these. Treatment with oxytocin was repeated at 30 minute intervals for 3 total doses. No coordinated uterine contractions were seen. Because oxytocin is slow to dissociate from myometrial receptors, continuing oxytocin therapy in the absence of response is not appropriate. The bitch was taken to C-section and delivered of four viable pups.