Mäkikallio K, Tekay A, Jouppila P
Department of Obstetrics and Gynecology, University of Oulu, Finland.
Ultrasound Obstet Gynecol. 1999 Sep;14(3):175-9. doi: 10.1046/j.1469-0705.1999.14030175.x.
To determine the relationship between the yolk sac and umbilicoplacental circulations during the first trimester of pregnancy.
Sixteen normal singleton pregnancies were included in this longitudinal study. Transvaginal ultrasonography with color and pulsed Doppler was performed at 5+, 7+, 8+ and 10+ gestational weeks. Fetal heart rate and blood velocity waveforms of yolk sac, umbilical and chorionic arteries were obtained.
The detection rate of arterial blood flow in the yolk sac increased significantly from 5+ (2/16) to 7+ gestational weeks (12/16). Thereafter, it declined significantly and no arterial blood flow was detected at 10+ weeks. When the arterial blood flow was observable in the yolk sac, all waveforms consisted of continuous diastolic blood flow. There were no significant changes in peak systolic velocity (PSV), time-averaged maximum velocity (TAMXV), pulsatility index (PI) or resistance index (RI) values of the yolk sac arteries during the study period. In umbilical arteries, blood flow was detected in two of 16 patients at 5+ weeks and in all cases thereafter. The mean umbilical artery PSV (SD) increased from 7.2 cm/s (3.7) at 8+ weeks to 13.0 cm/s (2.9) at 10+ weeks (p = 0.001). No changes in PI values were found and the absence of diastolic flow was typical of the umbilical artery during the study period. In chorionic arteries, blood flow was detected in six out of 16 subjects at the 5+ week, in 14 out of 16 patients at the 7+ week and in every case thereafter. No changes in PSV or TAMXV values were found.
Our results showed that the arterial signals in the yolk sac circulation disappeared and the umbilicoplacental circulation increased between 8+ and 10+ weeks of gestation. This indicates that the placenta replaces the yolk sac as an essential source of blood supply to the embryo at that time.
确定妊娠早期卵黄囊与脐胎盘循环之间的关系。
本纵向研究纳入了16例正常单胎妊娠。在妊娠5⁺、7⁺、8⁺和10⁺周时进行经阴道超声检查及彩色和脉冲多普勒检查。获取胎儿心率以及卵黄囊、脐动脉和绒毛膜动脉的血流速度波形。
卵黄囊中动脉血流的检出率从妊娠5⁺周时的2/16显著增加至7⁺周时的12/16。此后，其显著下降，在10⁺周时未检测到动脉血流。当卵黄囊中可观察到动脉血流时，所有波形均由持续的舒张期血流组成。在研究期间，卵黄囊动脉的收缩期峰值速度（PSV）、时间平均最大速度（TAMXV）、搏动指数（PI）或阻力指数（RI）值均无显著变化。在脐动脉中，16例患者中有2例在5⁺周时检测到血流，此后所有病例均检测到血流。脐动脉平均PSV（标准差）从8⁺周时的7.2 cm/s（3.7）增加至10⁺周时的13.0 cm/s（2.9）（p = 0.001）。PI值未发现变化，在研究期间脐动脉典型表现为无舒张期血流。在绒毛膜动脉中，16例受试者中有6例在5⁺周时检测到血流，7⁺周时16例患者中有14例检测到血流，此后所有病例均检测到血流。PSV或TAMXV值未发现变化。
我们的结果表明，在妊娠8⁺至10⁺周期间，卵黄囊循环中的动脉信号消失，脐胎盘循环增加。这表明此时胎盘取代卵黄囊成为胚胎血液供应的重要来源。
