Schwärzler P, Senat M V, Holden D, Bernard J P, Masroor T, Ville Y
Fetal Medicine Unit, St. George's Hospital Medical School, London, UK.
Ultrasound Obstet Gynecol. 1999 Aug;14(2):92-7. doi: 10.1046/j.1469-0705.1999.14020092.x.
To date, there have been no studies on the optimal timing of second-trimester ultrasound screening for fetal abnormalities. The purpose of this study was to investigate whether, of three gestational ages (18, 20 and 22 weeks), any one was associated with a significant advantage in terms of identification of abnormalities or need for further ultrasound assessment.
Prospective, randomized study of second-trimester unselected pregnant women, who had had an ultrasound examination with normal results at 10-14 weeks.
A total of 1206 women were randomized into three mutually exclusive groups relating to their second-trimester appointment for a screening ultrasound examination for fetal abnormalities in the second trimester of pregnancy: Group 1 at 18-18 + 6 weeks, Group 2 at 20-20 + 6 weeks and Group 3 at 22-22 + 6 weeks. The anomaly scans were carried out according to a standardized protocol. The fetuses were examined for structural and developmental abnormalities. Uterine artery Doppler measurements, including waveform recordings, were performed in all cases. The main end-points were the need for rescanning of all or part of the fetal anatomy, fetal outcome, placental localization, and incidence of notches in the uterine artery waveform.
The baseline demographic characteristics and risk factors in the three groups were similar and gestational age-related fetal measurements were comparable. There were significantly higher percentages of completed scans in Group 2 (90%) and Group 3 (88%) than in Group 1 (76%; p < 0.001), but no significant difference between those scanned at 20 and at 22 weeks. This was associated with a higher incidence of non-cephalic presentation in Group 1 (46%) than in the other two groups (36%, p < 0.001). Significant differences in completing the assessment of the thorax, heart, spine and skeleton were also observed. There was no significant difference in maternal body habitus, fetal movements or the occurrence of uterine fibroids between the study groups. The incidences of low-lying placenta and of abnormal uterine artery Doppler screening were also higher at 18 weeks than at 20 and 22 weeks (p < 0.001 for both variables), with no difference seen between Groups 2 and 3. The numbers of fetal anomalies detected in the three groups were three, two and two, respectively; these did not differ significantly between the groups.
This study suggests that, in an unselected pregnant population, second-trimester ultrasound screening is easier to perform and less likely to require an additional scan at 20-22 weeks than at 18 weeks.
迄今为止，尚无关于孕中期超声筛查胎儿异常最佳时机的研究。本研究的目的是调查在三个孕周（18、20和22周）中，是否有任何一个孕周在识别异常或进一步超声评估需求方面具有显著优势。
对孕中期未筛选的孕妇进行前瞻性随机研究，这些孕妇在10 - 14周时超声检查结果正常。
共有1206名妇女根据其孕中期预约进行妊娠中期胎儿异常筛查超声检查，随机分为三个相互排斥的组：第1组在18 - 18 + 6周，第2组在20 - 20 + 6周，第3组在22 - 22 + 6周。异常扫描按照标准化方案进行。对胎儿进行结构和发育异常检查。所有病例均进行子宫动脉多普勒测量，包括波形记录。主要终点是对全部或部分胎儿解剖结构进行再次扫描的需求、胎儿结局、胎盘定位以及子宫动脉波形切迹的发生率。
三组的基线人口统计学特征和危险因素相似，与孕周相关的胎儿测量值具有可比性。第2组（90%）和第3组（88%）完成扫描的百分比显著高于第1组（76%；p < 0.001），但20周和22周扫描的组间无显著差异。这与第1组（46%）非头先露发生率高于其他两组（36%，p < 0.001）相关。在完成胸部、心脏、脊柱和骨骼评估方面也观察到显著差异。研究组之间孕妇体型、胎儿活动或子宫肌瘤的发生情况无显著差异。18周时前置胎盘和子宫动脉多普勒筛查异常的发生率也高于20周和22周（两个变量p均 < 0.001），第2组和第3组之间无差异。三组中检测到的胎儿异常数量分别为3例、2例和2例；组间无显著差异。
本研究表明，在未筛选的孕妇群体中，孕中期超声筛查在20 - 22周比在18周更容易进行，且更不太可能需要额外扫描。
