The Ultrasonography In Monitoring The Development Of The Sheep Fetus

Eleven pregnant Xiaoweihanyang ewes were scanned by a B-mode real-time ultrasoundwith a 3.5MHz and a 7.5MHz transducer to monitor the fetal development. The resultSshowedtEmbryos and heart beating were first observed transrectally at l8 and 19 days ofpregnancy by a 7.5MHz linear-array transducer. Fetal head, body tnJnk and limb buds couldbe c1arified at 34 days of pregnancy and fetal movement and umbilical cord were observedat 38 days of pregnancy At 43 days of gestation. optic vesicle, fetal snout and hoofs couldbe seen. From day 30 to day 46 of gestation, the relationship between gestational age in daysand diameters of amniotic sac in milIimeters is expressed as: Y=0.565065X+18.75l790(Y-gestational days, X-diameters of amniolic sac), R'=0.9528(P<0.01). Placentome were firstobserved at day 32 of gestation and their diameters reached the maximum at week 11 ofpregnancy. From weeks 5 to I 1 of gestation, the relationship betWeen diameters ofpIacentome and gestational age can be expressed as f Y=4.96l429X-16.6557l4(Y-diameteof placentome, X-gestational week), R'=0.9882(P<0.01). Fetal skeleton wasn't calcificatedat the same time. however after week l5 of pregnancy, they all accomplished developmentand their sonic shadow could be seen from the ultrasonography. The reIationship betweengestational age and heart rate from weeks 5 to 2l of gestation is described by the equation fY=230.l76838-4.084897X(Y-heart rate, X-gestational week), R2= -0.8473(P<0.0l ). Fetalstomachs were first observed at week 8 of pregnancy. FetaI liver accompIished developmentat week 12 of gestation. Fetal kidney was first tnonitored at week 13 of gestation, then itdeveloped quickly in the following month. There was no difference between the datameasured by electronic calipers of the B-rnode uItrasound and the data obtained bypostmortem examination.The experiment adopted fOur fetometric parameters to determine the gestational ageamong which BPD (biparietal diameter) was most suitabIe. The relationship betweengestationai age and BPD from weeks 7 to l8 of pregnancy is described as f Y=3. l l0]66X-6.074771(Y-BPD. X-gestational week), R'=0.93l7(P<0.0l). From weeks 6 to 13 ofgestation, the equation between gestationaI age and head length is Y=7.158820X-32.604816(Y-head length, X-gestational week), R2=0.9981(P<0.05). The relationship between diameters of lateral thorax and gestational age from weeks 7 to 18 of gestation is expressed as: Y=4.849649X-24.921955(Y-diameters of lateral thorax, X-gestational week), R2=0.9838(P<0.05). From weeks 6 to 17 of pregnancy, the relationship between diameters of abdomen and gestational age is described by the linear equation: Y=5.504364X-23.124986(Y-diameters of abdomen, X-gestational week), R2=0.9828(P<0.05). Among these four fetometric parameters, fetal numbers had no effect on them.