Table 3.

Average percentage with a preterm birth and very preterm birth by timing of treatment initiation and the average risk ratio (RR) with average 95% confidence interval (CI) in the intent to treat versus naive analysis, adding measurement error

			Intent to treat analysis				Naïve analysis
Preterm Category	Measurement Error	Category	N	%	Average RR (95% CI)	Coverage interval	N	%	Average RR (95% CI)	Coverage interval
<37 weeks	+− 2 Weeks	Preconception	186	37.0	0.99 (0.85,1.17)	0.97	186	36.0	1.11 (0.96,1.31)	0.81
		During pregnancy	185	37.2	1		154	34.0	1
		Excluded women	-	-	-		31	69.9
	+− 5 Weeks	Preconception	211	42.0	1.00(0.87,1.16)	0.96	211	42.0	1.12 (0.96,1.32)	0.70
		During pregnancy	209	41.9	1	1	179	39.4	1	1
		Excluded women	-	-	-	-	30	67.6	-	-
<32 weeks	+− 2 Weeks	Preconception	38	7.5	0.99 (0.64,1.54)	0.94	38	7.5	1.42 (0.86,2.35)	0.73
		During pregnancy	38	7.6	1		25	5.5
		Excluded women	-				13	23.4
	+− 5 Weeks	Preconception	56	11.1	1.00 (0.70,1.42)	0.95	56	11.1	1.42 (0.94,2.13)	0.60
		During pregnancy	56	11.2	1	1	42	9.2	1	1
		Excluded women	-	-	-	-	14	32.0		-
<28 weeks	+− 2 Weeks	Preconception	9	1.7	0.96 (0.36,2.58)	0.97	9	1.7	2.17 (0.79,5.98)	0.81
		During pregnancy	9	1.8	1		4	1.0	1
		Excluded women	-	-	-		4	25.0	-
	+− 5 Weeks	Preconception	14	2.8	1.00 (0.47,2.14)	0.94	14	2.8	2.17 (0.79,5.98)	0.69
		During pregnancy	14	2.8		1	8	1.8		1
		Excluded women	-	-	-	-	6	12.7	-	-