. Author manuscript; available in PMC: 2022 Sep 1.

Published in final edited form as: Int J Gynaecol Obstet. 2021 Dec 13;158(3):605–612. doi: 10.1002/ijgo.14053

Table 2. Premature birth (<37 weeks of gestation) in the second live birth by preterm birth in the first live birth and inter-birth interval, 2001-2015 (n = 1,764,012).

Inter-birth interval	Preterm on first birth	Preterm on second birth
		Unadjusted		Adjusted^a
		OR	(95% CI)	OR	(95% CI)
<12 months	≥37 weeks	Reference		Reference
<12 months	<37 weeks	3·48	3·21 – 3.77	2.86	2.60 – 3.15
12 to 24 months	≥37 weeks	Reference		Reference
12 to 24 months	<37 weeks	2.97	2.88 – 3.06	2.54	2.45 – 2.63
≥24 months	≥37 weeks	Reference		Reference
≥24 months	< 37 weeks	2.70	2.65 – 2.75	2.53	2.48 – 2.58

Analysis adjusted by mother's residential area, household overcrowding, mother's self-declared race/skin color, mother's level of education, mother's marital status, number of prenatal visits, maternal age, type of delivery, and newborn's year of birth at the time of the first birth.