Table 1.

Risk factors associated with spontaneous preterm birth.

Risk Factors	OR	95% CI	Reference
Second trimester cervical length ≤2.50 cm	6.9	4.3–11.1	[8]
Vaginal bleeding in third trimester	5.9	5.1–6.9	[6]
Short interval between pregnancies (<12 months)	4.2	3.0–6.0	[6]
Previous preterm birth with a single newborn	2.62	1.99–3.44	[8]
Vaginal bleeding in first trimester	2.0	1.7–2.3	[6]
Periodontal disease	2.0	1.2–3.2	[6]
Prior cervical conization	1.7	1.24–2.35	[6]
Age younger than 18	1.7	1.02–3.08	[6]
Low socioeconomic condition	1.66	1.06–2.61	[8]
	1.75	1.65–1.86	[6]
Pregnancy with male fetus	1.51	1.02–2.24	[8]
Asymptomatic bacteriuria	1.5	1.2–1.9	[6]
Bacterial vaginosis	1.4	1.1–1.8	[6]
Family history of preterm birth	1.35	1.12–1.63	[8]
Maternal smoking	1.27	1.21–1.33	[8]
	1.7	1.3–2.2	[6]