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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.