Bromley B, Harlow B L, Laboda L A, Benacerraf B R
Department of Obstetrics and Gynecology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
Radiology. 1991 Feb;178(2):375-7. doi: 10.1148/radiology.178.2.1987595.
A nonbradycardiac fetal heart rate is associated with a low rate of spontaneous abortion (2%-4%). To determine criteria for predicting impending first-trimester loss when a normal fetal heart rate is identified sonographically, the authors studied 16 consecutively examined patients with pregnancies of 5.5-9 weeks gestation, a small sac size, and fetuses with normal cardiac activity. Mean sac size (MSS) was determined and a small sac was diagnosed when the difference between the MSS and crown-rump length (MSS--CR) was less than 5 mm. Fifty-two consecutively examined patients with pregnancies of 5.5-9 weeks gestation, normal sac size, and fetuses with normal heart rate formed the control group. An MSS--CR of 5 mm or greater was considered normal. Fifteen of the 16 patients (94%) with first-trimester small sacs had spontaneous abortions despite normal sonographic cardiac activity. Four of the 52 control patients (8%) with normal sac sizes had spontaneous abortions. The authors' data show that, despite the presence of fetal cardiac activity at the time of sonography, the usual reassurance provided to patients should be guarded when the sac size is small.
胎儿心率正常与自然流产率较低（2%-4%）相关。为了确定在超声检查发现胎儿心率正常时预测孕早期即将流产的标准，作者研究了16例连续接受检查的妊娠5.5-9周、孕囊较小且胎儿心脏活动正常的患者。测定平均孕囊大小（MSS），当MSS与头臀长度之差（MSS-CR）小于5mm时诊断为孕囊小。52例连续接受检查的妊娠5.5-9周、孕囊大小正常且胎儿心率正常的患者作为对照组。MSS-CR为5mm或更大被认为是正常的。16例孕早期孕囊小的患者中有15例（94%）尽管超声检查心脏活动正常仍发生了自然流产。52例孕囊大小正常的对照组患者中有4例（8%）发生了自然流产。作者的数据表明，尽管超声检查时存在胎儿心脏活动，但当孕囊较小时，向患者提供的常规安慰应谨慎。
