Stepwise multivariate linear regression using log hydroxybutyrate:glucose ratio as dependent variable
| Independent variable | Coefficient and 95% CI | p Value |
| Age (hours) | 1.02 (1.00 to 1.03) | 0.002 |
| Gestation | ||
| Post-term compared with term | 1.94 (1.37 to 2.75) | <0.001 |
| Birthweight (kg) | −1.57 (−1.99 to −1.23) | <0.001 |
| Rectal temperature (°C) | 1.31 (1.13 to 1.51) | <0.001 |
| Maternal free T4 | −1.04 (−1.07 to −1.01) | 0.006 |
| Infant free T4 | 1.02 (1.01 to 1.03) | <0.001 |
| Infant TSH (log values) | −1.95 (−3.03 to −1.25) | 0.003 |
| Sex | 1.33 (1.11 to 1.60) | 0.002 |
| Female compared with male | ||
| Antenatal care | −1.24 (−1.51 to −1.01) | 0.04 |
| Compared with none | ||
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The estimated effect on blood hydroxybutyrate/glucose ratio is the change in level for a unit increase in a continuous variable, or the stated categorical variable. The maternal and infant variables entered into the regression were maternal age, height, weight, haemoglobin, parity, social score, antenatal attendance and thyroid function; infant sex, birthweight, length, head circumference, haemoglobin, Apgar scores at one and five minutes, free T4 and TSH. Infant age at sampling was entered as an important potential confounder.
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Number of observations = 515
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Geometric mean of hydroxybutyrate ratio = 41 (min 0.2 to max 135)
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Adjusted R-squared = 0.25
