Table 4  Individual patient data meta-analysis: Prevention of preterm birth with vaginal progesterone in asymptomatic pregnant women (singleton pregnancies) with a short cervix on ultrasound (≤ 25 mm) before 24 + 0 WG 29 .

Outcome	Relative risk (RR) (95% CI)	p-value	NNT
a total neonatal morbidity and mortality: defined as the occurrence of one of the following events: respiratory distress syndrome, intraventricular haemorrhage, necrotising enterocolitis, documented neonatal sepsis, neonatal death b NICU = Neonatal Intensive Care Unit NNT = number needed to treat, * = primary outcome
Preterm birth < 28 WG	0.67 (0.45 – 0.99)	0.04	27
Preterm birth < 33 WG*	0.62 (0.47 – 0.81)	0.0006	12
Preterm birth < 35 WG	0.72 (0.58 – 0.89)	0.003	12
Respiratory distress syndrome	0.47 (0.27 – 0.81)	0.007	18
Total neonatal morbidity and mortality a	0.59 (0.38 – 0.91)	0.02	18
Birth weight < 1500 g	0.62 (0.44 – 0.86)	0.004	16
Admission to NICU b	0.68 (0.53 – 0.88)	0.003	13