Grand Rounds

Clinical and Examination Factors: A New Model for Predicting Spontaneous Late Preterm Birth

BACKGROUND AND PURPOSE:

Improved prediction models could help identify which women with late preterm labor will progress to delivery
Glover et al. (Amer J Perinatol, 2019) identified risk factors that are associated with late-preterm delivery in women with spontaneous late-preterm labor

Secondary analysis of Antenatal Betamethasone for Women at Risk for Late Preterm Delivery (ALPS) RCT (MFMU study)
Participants
- Singleton pregnancies at 34w0d to 36w5d (betamethasone vs placebo)
Late preterm definition: 34w0d to 36w6d
Groups
- Women who delivered at term
- Women who delivered preterm
Data analysis
- Optimal sensitivity and specificity of initial cervical dilation and effacement at predicting preterm birth were determined
- Multivariable regression was used to identify factors associated with late preterm delivery

732 women with late preterm labor | 431 (59%) delivered preterm
Cervical dilation ≥ 4 cm for prediction of late-preterm delivery
- 60% sensitivity | 68% specificity
- AUC = 0.64 (95% CI, 0.61–0.68)
Cervical effacement ≥ 75% for prediction of late-preterm delivery
- 59% sensitivity and 65% specificity
- AUC = 0.62 (95% CI, 0.58–0.65)
Factors associated with late preterm delivery
- Earlier gestational age at randomization: adjusted Odds Ratio (aOR) 0.8 (95% CI, 0.6 to 1; p=0.02)
- Nulliparity: aOR 1.7 (95% CI, 1.1 to 2.6; p=0.01)
- Fetal malpresentation: aOR 6.5 (95% CI, 0.8-53.6; 0.08)
Combining clinical and examination features significantly improved late preterm birth prediction
- 81% sensitivity | 48% specificity
- AUC = 0.72 (95% CI, 0.68–0.75; <0.01)

60% of women who experienced spontaneous late preterm labor will go on to deliver preterm
A combined analysis of examination and clinical features (e.g. gestational age, cervical dilation) improved the accuracy of late-preterm birth prediction but “overall models remained only modestly predictive”

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