. 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 3. Recurrent preterm birth (<37 weeks) in the third live birth by term vs preterm birth in the first and second live births and inter-birth interval, 2001-2015 (n = 544,665).

Inter-birth interval	First and second birth outcomes	Preterm on third birth
		Unadjusted		Adjusted^a
		OR	(95% CI)	OR	(95% CI)
<12 months	Term / Term	Reference		Reference
	Preterm / Term	1.91	1.55 – 2.35	1.75	1.38 – 2.21
	Term / Preterm	3.36	2.88 – 3.93	3.15	2.65 – 3.74
	Preterm / Preterm	7.55	5.88 – 9.70	6.53	4.91 – 8.69
	Term /Term	Reference		Reference
12 to 24 months	Preterm /Term	1.83	1.71 – 1.96	1.71	1.58 – 1.85
	Term / Preterm	2.77	2.62 – 2.93	2.59	2.43 – 2.76
	Preterm / Preterm	6.03	5.48 – 6.63	5.52	4.96 – 6.14
≥24 months	Term / Term	Reference		Reference
	Preterm / Term	1.79	1.72 – 1.86	1.74	1.66 – 1.82
	Term / Preterm	2.37	2.27 – 2.46	2.28	2.18 – 2.38
	Preterm / Preterm	4.79	4.49 – 5.12	4.64	4.31 – 4.98

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.