Skip to main content

Table 1 Pregnancy duration according to fetal size at 10–24 weeks of gestation.

From: Fetal size in the second trimester is associated with the duration of pregnancy, small fetuses having longer pregnancies

  HC AC FL
z-score Pregnancy duration (days) 95% CI Pregnancy duration (days) 95% CI Pregnancy duration (days) 95% CI
  Unadjusted results
-2.5 289.6 288.0, 291.1 289.0 287.4, 290.6 288.3 286.6, 289.9
-2.0 288.5 287.1, 289.8 288.0 286.6, 289.4 287.4 286.0, 288.8
-1.5 287.3 286.2, 288.4 287.0 285.8, 288.1 286.5 285.3, 287.6
-1.0 286.1 285.2, 287.0 285.9 284.9, 286.8 285.6 284.6, 286.5
-0.5 284.9 284.1, 285.6 284.7 284.0, 285.5 284.6 283.8, 285.3
0.0 283.6 282.8, 284.2 283.5 282.8, 284.2 283.6 282.8, 284.3
0.5 282.2 281.4, 283.0 282.3 281.5, 283.1 282.5 281.7, 283.3
1.0 280.8 279.7, 281.8 281.1 280.0, 282.1 281.4 280.3, 282.5
1.5 279.3 277.8, 280.7 279.7 278.3, 281.1 280.3 278.9, 281.7
2.0 277.7 275.8, 279.5 278.3 276.4, 280.1 279.1 277.3, 280.9
2.5 276.1 273.6, 278.4 276.9 274.4, 279.2 277.9 275.6, 280.1
P-value† <0.0001   <0.0001   <0.0001  
  Adjusted for the difference between LMP- and HC-based gestational ages.
-2.5 286.9 282.9, 290.4 286.6 284.5, 288.6 286.0 284.1, 287.8
-2.0 286.3 283.0, 289.2 286.0 284.2, 287.7 285.5 283.9, 287.1
-1.5 285.6 283.1, 287.9 285.4 284.0, 286.8 285.1 283.8, 286.3
-1.0 284.9 283.2, 286.6 284.8 283.7, 285.8 284.6 283.5, 285.5
-0.5 284.2 283.2, 285.3 284.2 283.4, 285.0 284.1 283.3, 284.8
0.0 283.5 282.8, 284.2 283.5 282.8, 284.2 283.5 282.8, 284.2
0.5 282.8 281.7, 283.9 282.9 282.0, 283.7 283.0 282.2, 283.8
1.0 282.1 280.2, 283.9 282.2 281.1, 283.4 282.5 281.4, 283.5
1.5 281.3 278.5, 284.0 281.6 280.0, 283.1 282.0 280.5, 283.3
2.0 280.6 276.6, 284.0 280.9 278.8, 282.8 281.4 279.6, 283.2
2.5 279.8 274.7, 284.1 280.2 277.5, 282.6 280.9 278.6, 283.0
P-value† 0.089   0.004   0.008  
  1. Pregnancy duration calculated from a certain and regular last menstrual period (LMP) in 541 pregnancies with spontaneous onset of labour are presented according to fetal size at 10–24 weeks of gestation, i.e. according to z-scores* of head circumference (HC), abdominal circumference (AC), and femur length (FL) in multivariable linear regression** (upper panel). Values for pregnancy duration when adjusted for the difference between LMP- and HC-based gestational ages are shown in the lower panel.
  2. * Z-scores according to gestational age specific means and standard deviations of each biometric measure.
  3. ** To normalize the data pregnancy duration used in the regression model are transformed to the power of 10.
  4. † Test for the association between z-score of each biometric measure and pregnancy duration.