Accuracy of prediction of canine litter size and gestational age with ultrasound

Abstract

Different sonographic criteria have been developed to estimate canine fetal age, including fetal mensuration and assessment of fetal organ development. This retrospective study assessed the accuracy of gestational age and litter size predictions in 76 bitches using one of two techniques. The first method used the differential features of fetal organ development that occur in early and mid pregnancy, based on published tables for beagles. The second method used biparietal head and trunk diameters to predict gestational age based on tables published for late gestational Labrador Retrievers. The accuracy of the two methods was compared and the effect of maternal body weight and litter size evaluated. Litter size and maternal body weight did not affect the accuracy of gestational age prediction. Using a combination of both methods, the overall accuracy of predicting parturition date within 65 +/- 1 day and +/- 2 days was 70.8% and 86.1%, respectively. The correct litter size was predicted in 65% of cases, and in 89.5% of cases for +/- 1 pup. Pearson's correlation between actual litter size and predicted litter size was high (R = 0.957, P < 0.001). The organ development method of predicting gestational age was more accurate than late gestational fetal mensuration (P = 0.019). The optimum time for sonographic estimation of fetal age and litter size is early and mid pregnancy.

Prediction of Parturition Date in the Bitch and Queen

“…Foetal number, however, cannot be accurately judged ultrasonographically. Because the entire uterus cannot be imaged within the same scan plane, the examiner may count some foetuses twice and miss others (Lenard et al. 2007).…”

“…In the dog, it is controversial whether pregnancy length and litter size are correlated (Okkens et al. 1993, 2001; Beccaglia and Luvoni 2006; Lenard et al. 2007).…”

Evaluation of the use of portable ultrasonography to determine pregnancy status and fecundity in bonnethead shark Sphyrna tiburo

“…This is also preferable to estimates made during early pregnancy because unfertilized or nonviable eggs are often observed in the uteri of some shark species including S. tiburo (Parsons, ) and, as shown in this study, are indistinguishable from fertile eggs at the pre‐embryo stage. However, assessments taken during mid‐pregnancy would still be unable to differentiate between live embryos and those that underwent early embryo death; a problem also experienced in this study as well as in earlier efforts to use ultrasonography to estimate canine litter size (Lenard et al ., ).…”

“…As with pregnancy assessments, fecundity estimates obtained using ultrasonography were occasionally inaccurate, although they did not differ significantly in comparison with dissection results. Comparable differences have been observed between in utero litter‐size estimates obtained using ultrasonography and other methods ( e.g ., radiography, post‐mortem embryo or placental‐scar counts) in other viviparous animals such as female dogs (Lenard et al ., ), hares (Griffin & Mills, ), wolves (McNay et al ., ) and sheep (Taverne et al ., ); therefore, these findings were not unexpected. Not unlike pregnancy misdiagnoses, embryo miscounts were due to several factors including the difficulties in detecting the presence of early‐stage embryos prior to skeletal mineralization and artefacts caused by sound wave interference from other organs such as the gut.…”

Efficiency of vaginal electrical impedance to determine the stage of the reproductive cycle in bitches

“…This method is not satisfactory given that the ovulation time is not fixed in the 5 to 30 day period of estrous. Therefore, various methods for predicting ovulation, including serum or plasma hormone concentration, vaginal cytology, vaginal electrical impedance (VEI), vaginal endoscopy and ultrasonography (USG) evaluation of the ovary, have been employed (3,7,9,10).…”