Factors contributing to the decision to perform a cesarean section in Labrador retrievers

Abstract

Background: In the past 10 years, the frequency of unplanned cesarean sections in the Labrador Retriever breeding colony at Guiding Eyes for the Blind stayed around 10% (range 5% to 28%). To reduce the number of cesarean sections, factors influencing the occurrence of a cesarean section need to be known. The goal of this study was to identify factors that contribute to the decision to perform a cesarean section.

Results: Of the 688 Labrador Retriever litters whelped between 2003 and 2016, 667 litters had sufficient data and remained in the analysis. The target trait was ordinal with the three levels "normal whelping", "assisted whelping" and "cesarean section". A general ordinal logistic regression approach was used to analyze the data. Model selection with possible predictors resulted in a final model including weight of the dam, the weight of the heaviest puppy of a litter, the number of fetuses malpositioned and the quality of uterine contractions. Weight and size of a litter, parity, maternal inbreeding coefficient, whelping season, dam and sire were dropped from the model because they were not significant. The risk of a cesarean section was influenced by the combination of the weight of the dam and the weight of the heaviest puppy in the litter, as well as by the number of malpositioned fetuses and the quality of the contractions. Larger puppies increased the risk of cesarean section especially when the dam had a lighter weight. For dams weighing 23.6 kg and 32.8 kg the predicted probability of a cesarean section was low, with 0.06 and 0.02, respectively, when the heaviest puppy in a litter was light (0.42 kg), contractions were normal and no fetus was malpositioned. However, the probability of a cesarean section was much higher, ranging from 0.24 to 0.08, when the heaviest puppy in a litter was heavy (0.66 kg).

Conclusions: Means to reduce the cesarean section frequency in this Labrador Retriever breeding colony should include genetic selection for ideal puppy weight. In addition, dams with an adult body weight substantially below average should not be selected as breeders in this colony.

Keywords: Assisted delivery; Cesarean section; Labrador retriever; Risk factors.

Fig. 1

Predicted probabilities of EOW outcomes if contractions are normal and no malpositioned fetus is present. On the y-axis are the predicted probabilities of the nine outcomes of the target trait EOW for the weight of the dam ranging from the mean – 2sd (23.6 kg) to the mean + 2sd (32.8 kg) on the x-axis. HPW is the weight of the heaviest puppy in a litter in kg. All predicted probabilities are significantly different from zero

Fig. 2

Predicted probabilities of EOW outcomes if contractions are poor and no malpositioned fetus is present. On the y-axis are the predicted probabilities of the nine outcomes of the target trait EOW for the weight of the dam ranging from the mean – 2sd (23.6 kg) to the mean + 2sd (32.8 kg) on the x-axis. HPW is the weight of the heaviest puppy in a litter in kg. All predicted probabilities are significantly different from zero with the exception of the estimate for a c-section at 32.8 kg in the case of a light heaviest puppy and the estimates at 23.6 kg in the case of a heavy heaviest puppy

Fig. 3

Predicted probabilities of EOW outcomes if contractions are normal and one fetus is malpositioned. On the y-axis are the predicted probabilities of the nine outcomes of the target trait EOW for the weight of the dam ranging from the mean – 2sd (23.6 kg) to the mean + 2sd (32.8 kg) on the x-axis. HPW is the weight of the heaviest puppy in a litter in kg. All predicted probabilities are significantly different from zero

Fig. 4

Predicted probabilities of EOW outcomes if contractions are poor and one fetus is malpositioned. On the y-axis are the predicted probabilities of the nine outcomes of the target trait EOW for the weight of the dam ranging from the mean – 2sd (23.6 kg) to the mean + 2sd (32.8 kg) on the x-axis. HPW is the weight of the heaviest puppy in a litter in kg. All predicted probabilities for a normal delivery, as well as for an assisted delivery of a heavy heaviest puppy, are not significantly different from zero whereas all others are

Fig. 5

Predicted probabilities of EOW outcomes if contractions are normal and the weight of the heaviest puppy in a litter is 0.54 kg. On the y-axis are the predicted probabilities of the nine outcomes of the target trait EOW for the number of malpositioned fetuses ranging from 0 to 3 or more on the x-axis. DWT is the adult weight of the dam in kg. All predicted probabilities are significantly different from zero with the exception of a normal delivery in the case of 3 or more malpositioned fetuses, regardless of the weight of the dam

Fig. 6

Predicted probabilities of EOW outcomes if contractions are poor and the weight of the heaviest puppy in a litter is 0.54 kg. On the y-axis are the predicted probabilities of the nine outcomes of the target trait EOW for the number of malpositioned fetuses ranging from 0 to 3 or more on the x-axis. DWT is the adult weight of the dam in kg. If the number of malpositioned fetuses is one or more, predicted probabilities for a normal delivery are not significantly different from zero, regardless of the weight of the dam. If the number of malpositioned fetuses is two or more, predicted probabilities for an assisted delivery are not significantly different from zero, regardless of the weight of the dam. All other predicted probabilities are significantly different from zero