Yeager A E, Mohammed H O, Meyers-Wallen V, Vannerson L, Concannon P W
Department of Clinical Sciences, New York State College of Veterinary Medicine, Cornell University, Ithaca 14853.
Am J Vet Res. 1992 Mar;53(3):342-51.
Serial ultrasonographic examinations were performed on 8 Beagle bitches from 20 to 60 days pregnant to determine time of first detection, appearance, and sizes of selected features of pregnancy. Gestation was timed from the day of the preovulatory luteinizing hormone surge. Findings related to gestational age were consistent among bitches. Gestational ages at earliest detection of the following features were: chorionic cavity at day 20; placental layers in the uterine wall at day 22 to 24; zonary placenta at day 27 to 30; embryo and heartbeat at day 23 to 25; yolk sac membrane at day 25 to 28; allantoic membrane at day 27 to 31; choroid plexus of the brain at day 31 to 35; fetal movement at day 34 to 36; skeleton at day 33 to 39; bladder and stomach at day 35 to 39; kidney at day 39 to 47; and liver hypoechoic, compared with lung, at day 38 to 42. Extra-fetal structures were measurable from day 20 or 22 through day 48. Chorionic cavity diameter increased from 0.2 +/- 0.0 cm to 3.3 +/- 0.2 cm, outer uterine diameter increased from 0.8 +/- 0.03 cm to 4.8 +/- 0.2 cm, length of chorionic cavity or zonary placenta increased from 0.3 +/- 0.03 cm to 4.9 +/- 0.05 cm, uterine wall thickness increased from 0.3 +/- 0.03 cm to 0.8 +/- 0.01 cm, and placental thickness increased from 0.1 +/- 0.0 cm to 0.5 +/- 0.05 cm. Chorionic cavity diameter, outer uterine diameter, and placental length each increased at a linear rate through day 37, after which time, each had a marked plateau in growth. Of the extra-fetal structures, chorionic cavity diameter was the most accurate for estimation of gestational age. All of the fetal structures studied increased at an increasing (second order) rate. Crown-rump length increased from 0.3 +/- 0.05 cm on day 24 to 9.2 +/- 0.2 cm on day 48. Body diameter increased from 0.2 +/- 0.03 cm on day 24 to 4.6 +/- 0.15 cm on day 60. Head diameter increased from 0.8 +/- 0.05 cm on day 34 to 2.7 +/- 0.04 cm on day 60. Of the fetal structures, head diameter was the most accurate for estimation of gestational age.
对8只怀孕20至60天的比格犬进行了系列超声检查，以确定首次检测到妊娠选定特征的时间、其出现情况及大小。妊娠期从排卵前促黄体生成素激增之日开始计算。母犬之间与妊娠年龄相关的检查结果一致。最早检测到以下特征时的妊娠年龄分别为：第20天出现绒毛膜腔；第22至24天子宫壁出现胎盘层；第27至30天出现带状胎盘；第23至25天出现胚胎及心跳；第25至28天出现卵黄囊膜；第27至31天出现尿囊膜；第31至35天出现脑脉络丛；第34至36天出现胎儿活动；第33至39天出现骨骼；第35至39天出现膀胱和胃；第39至47天出现肾脏；第38至42天肝脏与肺相比呈低回声。胎儿外结构从第20或22天至第48天均可测量。绒毛膜腔直径从0.2±0.0厘米增加至3.3±0.2厘米，子宫外径从0.8±0.03厘米增加至4.8±0.2厘米，绒毛膜腔或带状胎盘长度从0.3±0.03厘米增加至4.9±0.05厘米，子宫壁厚度从0.3±0.03厘米增加至0.8±0.01厘米，胎盘厚度从0.1±0.0厘米增加至0.5±0.05厘米。绒毛膜腔直径、子宫外径和胎盘长度在第37天前均以线性速率增加，此后，各自的生长均出现明显平台期。在胎儿外结构中，绒毛膜腔直径对妊娠年龄的估计最为准确。所有研究的胎儿结构均以递增（二阶）速率生长。顶臀长从第24天的0.3±0.05厘米增加至第48天的9.2±0.2厘米。身体直径从第24天的0.2±0.03厘米增加至第60天的4.6±0.15厘米。头部直径从第34天的0.8±0.05厘米增加至第60天的2.7±0.04厘米。在胎儿结构中，头部直径对妊娠年龄的估计最为准确。
