Prediction of parturition in dogs and cats : accuracy at different gestational ages

In bitches and queens, the ultrasonographic measurement of
extrafoetal and foetal structures allows the evaluation of
gestational age and the prediction of the parturition term for
an extended period of time. The aim of this study was to
investigate whether the accuracy of parturition date prediction
is affected by the week of pregnancy when the ultrasonographic
examination is performed. The results were obtained by
retrospective analysis on the gestational period basis (from
week 4 to week 9 of pregnancy) in 495 ultrasonographic
examinations of pregnant bitches (small and medium size) and
60 of pregnant queens. They demonstrated that a similar
accuracy (p > 0.05) was obtained by the measurement of inner
chorionic cavity at week 4 and 5 of pregnancy (±1 day, 81% vs
67.7%; ±2 days, 93.1% vs 85.9%). Accuracy (±1 day) based on
biparietal (BP) measurement was similar at week 5 and 6 of
pregnancy (78.6% vs 78.9%; p > 0.05), whereas a significant
decrease (p < 0.05) was observed at week 7 and 8 compared to
week 6. No difference in the accuracy of the prediction at
±2 days based on BP was observed from week 5 to 8 of
gestation (range from 82.3% to 95.2%). Close to term (week 9),
the accuracies of the prediction based on BP were significantly
lower than those obtained at week 5 (±1 day: 50.9% vs 78.6%,
p < 0.05; ±2 days: 69.8% vs 95.2%, p < 0.005). The accuracy
of the prediction in bitches and queens is influenced by the
gestational period when ultrasonographic measurements are
performed, particularly for BP measurement. Although a
decrease in BP accuracy occurs along the pregnancy, the
accuracy at ±1 and ±2 days of prediction of parturition term is
highly consistent for 6 and 8 weeks of gestation, respectively.