Table 1 

CTI dependency on gestational age. Dependency of fetal cardiac time intervals on gestational age (in weeks): coefficients of determination (r^{2}), yintercepts, slopes and the pvalue of the slopes (values < .05 in bold type). Linear regression parameters are given for each disjunct interval (upper rows) and each composite interval (lower rows). Nonlinear regression parameters are also given for those intervals in which an improved model fit was found (quadratic: PQ and PR interval, double logarithmic: QRS complex). 

regression type 
N 
r^{2} 
yintercept (ms) 
slope (ms/week) 
p 
slope (ms/week^{2}) 
p 



P wave 
linear 
228 
0.67 
14.0 
1.37 
<0.001 

PQ interval 
linear 
228 
0.07 
67.7 
0.49 
<0.001 

PQ interval 
nonlinear 
228 
0.13 
14.2 
3.38 
0.021 
0.07 
0.008 
QRS complex 
linear 
230 
0.62 
19.3 
0.92 
<0.001 

ln (QRS) 
nonlinear 
230 
0.66 
1.8 
0.60* 
<0.001 

ST segment 
linear 
217 
0.01 
60.4 
0.32 
0.169 

T wave 
linear 
216 
0.00 
126.0 
0.00 
1.000 

PR interval 
linear 
228 
0.16 
81.7 
0.88 
<0.001 

PR interval 
nonlinear 
228 
0.21 
20.0 
5.35 
<0.001 
0.08 
0.002 
QT interval 
linear 
216 
0.07 
205.8 
1.24 
<0.001 

QTc interval 
linear 
216 
0.06 
326.6 
1.65 
<0.001 



* the slope in this regression equation is ms/ln(week) 

van Leeuwen et al. BMC Pregnancy and Childbirth 2004 4:6 doi:10.1186/1471239346 