Porter T F, Dildy G A, Blanchard J R, Kochenour N K, Clark S L
Department of Obstetrics and Gynecology, University of Utah, Salt Lake City, USA.
Obstet Gynecol. 1996 May;87(5 Pt 1):699-702. doi: 10.1016/0029-7844(96)00006-3.
To establish the gestational age trends of amniotic fluid index (AFI) in uncomplicated twin pregnancies.
Amniotic fluid index was measured in uncomplicated twin pregnancies seen between 1985 and 1993 and meeting the following criteria: 1) no maternal medical or obstetric complications, 2) normal growth of both twins by serial ultrasound, and 3) normal amniotic fluid volume by ultrasound. Amniotic fluid index was measured by adding the deepest vertical pockets in four quadrants, defined by the umbilicus and linea nigra. The relation between gestational age and AFI was evaluated using linear regression analysis.
Two hundred eighty-two sets of twins were considered uncomplicated; 1101 AFI measurements were performed on these pregnancies between 25.5 and 40.5 weeks' gestation. Percentile values for AFI were determined according to gestational age. The regression equation relating the median AFI to gestational age was: AFI = 19.4 - 0.12 x gestational age (P = .03). The R2 value was 0.04.
Gestational age trends in normative AFI measurements for twin pregnancies have been established. Their use will facilitate a more reproducible, quantitative diagnosis of oligohydramnios in twins, compared with subjective, qualitative approaches to amniotic fluid volume assessment.
确定无并发症双胎妊娠羊水指数（AFI）随孕周的变化趋势。
对1985年至1993年间就诊的无并发症双胎妊娠进行羊水指数测量，这些妊娠符合以下标准：1）无母体医学或产科并发症；2）通过系列超声检查显示双胎生长正常；3）超声检查显示羊水量正常。羊水指数通过测量由脐部和腹白线界定的四个象限中最深的垂直羊水池深度并相加得出。采用线性回归分析评估孕周与AFI之间的关系。
282对双胎被认为无并发症；在这些妊娠的25.5至40.5孕周期间进行了1101次AFI测量。根据孕周确定AFI的百分位数。将中位数AFI与孕周相关的回归方程为：AFI = 19.4 - 0.12×孕周（P = 0.03）。R²值为0.04。
已确定双胎妊娠正常AFI测量值随孕周的变化趋势。与主观、定性的羊水量评估方法相比，其应用将有助于对双胎羊水过少进行更可重复、定量的诊断。
