Timing of delivery in a high-risk obstetric population: a clinical prediction model

Table 2 Risk factors included in the final model predicting delivery within 7 days of admission

Risk factor	OR [95% CI]	Adjusted OR^a [95% CI]
Maternal age (yr)
< 40	Reference	Reference
≥ 40	0.55 [0.39–0.78]	0.66 [0.45–0.97]
Parity
Nulliparous	Reference	Reference
Parity ≥1	0.68 [0.59–0.78]	0.58 [0.50–0.68]
Smoking during pregnancy^b	1.35 [1.13–1.62]	1.37 [1.12–1.67]
Gestational age (GA) on admission^c	1.08 [1.03–1.13]	^c
Maternal conditions
Preterm labour	2.38 [2.05–2.76]	7.37 [5.85–9.29]
PPROM	1.52 [1.30–1.76]	5.59 [4.42–7.07]
Prolapsed membranes	1.75 [1.41–2.18]	6.36 [4.77–8.48]
Associated antepartum haemorrhage	2.06 [1.63–2.60]	1.96 [1.53–2.52]

OR odds ratio, PPROM preterm pre-labour rupture of membranes
^aadjusted for all other factors presented in the table
^bmissing values were imputed
^cGestational age was modelled using higher order polynomials (see the equation below)
Equation:
Risk score =12.13 – [0.41 × Maternal age ≥ 40years] – [1.08 × GA] + [0.02 × (GA)²] – [0.54 × Parity] + [0.32 × Smoking] + [2.00 × Preterm labour] + [1.72 × PPROM] + [1.85 × Prolapsed membranes] + [0.67 × Antepartum haemorrhage]
the probability of outcome (delivery <7 days) = 1/(1 + e^{-risk score})

ISSN: 1471-2393