Is IVF/ICSI an Independent Risk Factor for Spontaneous Preterm Birth in Singletons? A Population-Based Cohort Study

Table 3

Multivariate analysis of risk factors for spontaneous preterm birth before 32 weeks and between 32 and 36 6/7 weeks of gestation, Slovenia, 2002–2015.

Preterm birth	before 32 weeks				between 32 to 36 and 6/7 weeks
	Odds ratio	95% confidence interval		p value	Odds ratio	95% confidence interval		p value
Covariates		Lower	Upper			Lower	Upper
Maternal age < 25
25–29 years	1,025	0,878	1,196	0,758	1,031	0,966	1,099	0,358
30–35 years	1,127	0,956	1,329	0,153	1,106	1,032	1,185	0,005
35–39 years	1,496	1,237	1,809	< 0,001	1,309	1,204	1,424	< 0,001
40 ≥	1,975	1,491	2,617	< 0,001	1,594	1,390	1,828	< 0,001
Maternal education: Tertiary
Secondary or professional	1,232	1,098	1,382	<0,001	1,074	1,020	1,13	0,006
Vocational	1,282	1,102	1,491	0,001	1,148	1,073	1,228	< 0,001
Primary or less	1,801	1,456	2,227	< 0,001	1,423	1,289	1,572	< 0,001
Not stated	0,712	0,588	0,861	< 0,001	1,077	1,005	1,154	0,037
Second birth
First birth	1,443	1,293	1,611	<0,001	1,426	1,36	1,496	< 0,001
Third birth or more	1,143	0,979	1,335	0,092	1,093	1,019	1,171	0,012
Smoking during pregnancy	1,445	1,265	1,650	<0,001	1,313	1,237	1,395	< 0,001
BMI 18.5 – 24.9 kg/m^2
BMI < 18.5 kg/m^2	1,604	1,341	1,917	<0,001	1,456	1,346	1,576	< 0,001
BMI 25 – 29.9 kg/m^2	1,021	0,9	1,158	0,749	0,935	0,884	0,989	0,018
BMI 30 kg/m^2 ≥	1,207	1,025	1,422	0,024	0,918	0,849	0,994	0,034
Heart, renal, pulmonary illness	1,255	0,928	1,698	0,141	1,135	0,986	1,308	0,078
Pregnant after IVF/ICSI	1,555	1,256	1,925	< 0,001	1,300	1,159	1,459	< 0,001
No cervical excision procedure
Cold knife conization	6,162	5,024	7,557	< 0,001	2,455	2,137	2,821	< 0,001
Other – LLETZ	2,735	2,162	3,460	< 0,001	1,770	1,56	2,007	< 0,001
Resection of uterine septum	2,858	2,454	3,328	< 0,001	1,369	1,249	1,500	< 0,001
Other uterine malformation	2,401	1,690	3,413	< 0,001	2,404	2,043	2,828	< 0,001
Preeclampsia / HELLP	1,595	1,199	2,122	0,001	1,316	1,144	1,513	< 0,001
Bleeding in pregnancy	3,078	2,734	3,465	<0,001	1,853	1,74	1,974	< 0,001