Study on fetal heart rate variation using a probability distribution matrix

1. 我们设计了一种新的方法，使用概率分布矩阵来同时描述胎儿心率（FHR）特征的变化以及当前和随后的心跳差（DFHR）。在矩阵的相应元素中绘制了fhr的列，dfhr的行和概率。分析了743例妊娠23-40周胎儿FHR数据的年龄相关性变化。妊娠前期FHR vs DFHR出现了三种特殊的概率分布模式。所提出的概率分布矩阵使人们能够将任意数量的FHR数据浓缩成一个统一的描述。这样就可以对数据进行整体分析，在同等规模上实现定量的组间比较。本文采用概率分布矩阵分析了12例妊娠25-32周无脑胎儿和165例妊娠正常胎儿的FHR数据，以阐明控制妊娠早期胎儿心率变化的脑区。妊娠27-28周和29-30周是胎儿脑功能发育与FHR变化的关键时期。在早期，延髓在FHR的变化中起作用，而在后期，头部延髓的大脑似乎也承担FHR调节剂的作用。为了确定充分评估各种胎儿状况所需的最小fhr数，分析了743例妊娠23 ~ 40周正常胎儿的9个连续两周间隔概率分布矩阵。在妊娠23-40周评估胎儿的最低fhr数几乎相同，在9,000到10,000之间，具有67-75%的基线变异性（即所谓的搏动变异性）和25-33%的长期变异性，无论妊娠是否提前。

1. We devised a new method using a probability distribution matrix to simultaneously describe variation in the characteristics of fetal heart rate (FHR) and beat-to beat difference (DFHR) between the present and the immediately following FHR.The FHRs were plotted in columns, DFHRs in rows and probabilities in the corresponding elements of the matrix. Analyzed were the age-related changes of FHR data obtained from 743 fetuses at 23-40 weeks' gestation using a pulsed Doppler cardiotocograph with autocorrelation. Three particular probability distribution patterns of FHR vs. DFHR emerged with advance in gestation. The probability distribution matrix presented enables one to condense any amount of FHR data, into one uniform description. This allows analysis of data, en bloc, achieving quantitative inter-group comparison, on an equivalent scale.2. To elucidate the brain segment which would control heart rate changes in human fetuses with advancing gestation, FHR data obtained from 12 anencephalic and 165 uncomplicated fetuses between 25-32 weeks' gestation were analyzed using a probability distribution matrix. There was a critical period between 27-28 and 29-30 weeks' gestation with regard to the developing brain function pertaining to FHR changes. In the early stage, the medulla oblongata plays a role in FHR changes, whereas, in the latter stage, the brain cephalad to the medulla also appears to take on the role of FHR regulator.3. To determine the minimum number of FHRs needed to assess various fetal conditions adequately, analyzed were 9 consecutive two-week interval probability distribution matrices obtained from 743 normal fetuses between 23 and 40 weeks' gestation. The minimum number of FHRs for assessment of the fetus at 23-40 weeks' gestation was almost the same, between 9,000 and 10,000, with 67-75% baseline variability (so called beat-to-beat variability) and 25-33% long-term variability regardless of advance in gestation.