Uterine fibroids and risk of preterm birth by clinical subtypes: a prospective cohort study

Table 2 Relationship between fibroid characteristics and preterm birth, Right from the Start, 2000–2012 (n = 4,622)

Fibroid Characteristic	Preterm Births (n = 352)		Term Births (n = 4,270)		Crude RR	95% CI	Adjusted RR^a	95% CI
Fibroid Characteristic	n	%	n	%	Crude RR	95% CI	Adjusted RR^a	95% CI
Fibroid Present
No	316	89.8	3,831	89.7	1.00	Referent	1.00	Referent
Yes	36	10.2	439	10.3	0.99	0.71–1.39	0.88	0.62–1.24
Fibroids, no.
0	316	89.8	3,831	89.7	1.00	Referent	1.00	Referent
1	21	6.0	315	7.4	0.82	0.53–1.26	0.76	0.49–1.16
≥ 2	15	4.3	124	2.9	1.42	0.87–2.31	1.14	0.68–1.89
Total Volume^b
No fibroids	316	89.8	3,831	89.7	1.00	Referent	1.00	Referent
First quartile	5	1.4	114	2.7	0.55	0.23–1.31	0.55	0.23–1.30
Second quartile	11	3.1	107	2.5	1.22	0.69–2.17	1.12	0.63–1.99
Third quartile	10	2.8	110	2.6	1.09	0.60–2.00	0.95	0.52–1.74
Fourth quartile	10	2.8	108	2.5	1.11	0.61–2.03	0.87	0.47–1.60
Largest Volume^c
No fibroids	316	89.8	3,831	89.7	1.00	Referent	1.00	Referent
First quartile	5	1.4	115	2.7	0.55	0.23–1.30	0.55	0.23–1.31
Second quartile	11	3.1	106	2.5	1.23	0.70–2.19	1.10	0.62–1.97
Third quartile	7	2.0	112	2.6	0.77	0.37–1.60	0.66	0.32–1.37
Fourth quartile	13	3.7	106	2.5	1.43	0.85–2.42	1.14	0.67–1.95
Fibroid Type^d
Any submucosal	7	2.0	62	1.5	1.33	0.65–2.71	1.09	0.53–2.23
Any intramural	15	4.3	193	4.5	0.95	0.57–1.56	0.81	0.49–1.35
Any subserosal	16	4.5	185	4.3	1.04	0.65–1.69	0.91	0.56–1.49
Any pedunculated	3	0.9	28	0.7	1.27	0.43–3.74	0.99	0.33–2.93
Location ^d
Any cervix	6	1.7	64	1.5	1.12	0.52–2.44	1.03	0.47–2.23
Any fundus	16	4.5	172	4.0	1.12	0.69–1.81	0.93	0.57–1.52
Any corpus	21	6.0	242	5.7	1.05	0.69–1.60	0.90	0.58–1.39

Abbreviations: RR Risk ratio, CI Confidence interval
^a Adjusted for maternal age and race/ethnicity
^b Quartiles for total fibroid volume: < 0.97 cm³, 0.97–4.76 cm³, 4.77–20.84 cm³, > 20.84 cm³
^c Quartiles for largest fibroid volume: < 0.82 cm³, 0.82–4.62 cm³, 4.63–18.18 cm³, > 18.18 cm³
^d Columns do not add up to 100% because a participant could contribute to more than one category if she had multiple fibroids, each category is a separate model with women without fibroids as referent group

ISSN: 1471-2393