Fertility treatments and the risk of preterm birth among women with subfertility: a linked-data retrospective cohort study

Table 1 Characteristics of women by preterm birth (< 37 weeks gestational age)

	Term (> 37 weeks)		Preterm (< 37)		Total		P value
	N	Row%	N	Row%	N	Col%	P value
Maternal age at delivery
≤ 30	290	81.7%	65	18.3%	355	72.4%	0.669
31+	108	80.0%	27	20.0%	135	27.6%
Paternal age at delivery
≤ 30	239	83.0%	49	17.0%	288	58.9%	0.223
31+	158	78.6%	43	21.4%	201	41.1%
BMI category (pre-pregnancy)
Underweight/Normal	184	76.0%	58	24.0%	242	55.1%	0.148
Overweight/Obese	161	81.7%	36	18.3%	197	4.9%
Income (at interview)
Less than $50,000	110	81.5%	25	18.5%	135	28.7%	0.938
50,000–$99,999	213	80.1%	53	19.9%	266	56.6%
Over $100,000	56	81.2%	13	18.8%	69	14.7%
Education level (at interview)
Less than college grad	127	77.4%	37	22.6%	164	33.6%	0.136
College grad or more	269	83.0%	55	17.0%	324	66.4%
Race/Ethnicity
White, non-Hispanic	381	80.9%	90	19.1%	471	96.1%	0.348
Hispanic, other non-White	17	89.5%	2	10.5%	19	3.9%
Religion
Non-LDS	84	78.5%	23	21.5%	107	21.8%	0.415
Latter-day Saint	314	82.0%	69	18.0%	383	78.2%
Attempt duration to conception
< 12 months	69	81.2%	16	18.8%	85	17.4%	0.771
12 to < 24	100	81.3%	23	18.7%	123	25.2%
24 to < 36	73	85.9%	12	14.1%	85	17.4%
36 to < 48	58	79.5%	15	20.5%	73	14.9%
48+	97	78.9%	26	21.1%	123	25.2%
Recruitment cohort
Clinic	203	76.3%	63	23.7%	266	54.3%	0.002
Population	195	87.1%	29	12.9%	224	45.7%
Baby sex
F	188	79.0%	50	21.0%	238	48.6%	0.219
M	210	83.3%	42	16.7%	252	51.4%
Multiplicity
Singleton	374	90.8%	38	9.2%	412	84.1%	0.000
Twins	24	33.8%	47	66.2%	71	14.5%
Triplets	0	0.0%	7	100.0%	7	1.4%
Treatment in cycle of conception
None	190	89.2%	23	10.8%	214	43.5%	0.001
Drugs	61	79.2%	16	20.8%	77	15.7%
IUI	48	75.0%	16	25.0%	64	13.1%
IVF	99	72.8%	37	27.2%	136	27.8%
Total	398	81.2%	92	18.8%	490	100.0%

ISSN: 1742-4755