Table 3.

Predicted height per linear spline period in girls from the non-manual social class, manual social class, and the mean difference in predicted height comparing girls from the manual with the non-manual social class

	Mean height, cm (SD)		Mean difference in height, cm (95% CI) manual – non-manual social class
	non-manual social class	manual social class
Fractional polynomial model
Birth	49.786 (1.532)	49.299 (1.516)	−0.487 (−0.669 to −0.306)
3 months	60.897 (1.655)	60.651 (1.682)	−0.246 (−0.386 to −0.106)
1 year	74.198 (2.081)	73.920 (2.098)	−0.278 (−0.445 to −0.110)
3 years	95.103 (3.053)	94.604 (3.013)	−0.499 (−0.728 to −0.270)
10 years	138.614 (5.754)	137.355 (5.530)	−1.259 (−1.723 to −0.795)
Linear spline model
Birth	50.173 (1.642)	49.734 (1.652)	−0.439 (−0.599 to −0.279)
3 months	60.833 (1.921)	60.654 (1.958)	−0.179 (−0.385 to 0.028)
1 year	75.466 (2.202)	75.267 (2.233)	−0.199 (−0.410 to 0.011)
3 years	95.529 (3.287)	94.958 (3.238)	−0.570 (−0.850 to −0.291)
10 years	140.167 (5.745)	138.948 (5.476)	−1.219 (−1.709 to −0.729)