A comparative study about the time of pregnancy and gestational age of SD rats by three methods

Objective To explore more accurate method about the time of pregnancy and gestational age of SD rats. Methods 7 to 8-week-old SD rats (18 females, 6 males) were selected, the ratios of male to female were 2∶1, 5∶2, 1∶1 and 4∶1.Through vaginal plug observation, vaginal smear method, weight comparison method to verify the exact date of pregnancy in the next morning. Results Vaginal observed at milky vaginal plug sperm could be observed as sickle rat sperm head.Body weight of pregnant rats changed obviously.Three detection methods were used to detect the pregnancy time for 18 females.The positive rate of vaginal plug observation was 5.6%.The positive rate of vaginal smear method was 44.4%.The false negative rate of vaginal smear method was 11.1%.The positive rate of body weight method was 11.1%.The false positive rate was 5.6%. Conclusion The accuracy of vaginal smear is higher than the vaginal plug method and weight comparison method, the vaginal plug method can be used as the premise of the other two methods.Comparison method can be used as supplementary that the other two methods missed. Key words: SD rat; Vaginal plugs; Vaginal smears