Table 2.

Three-Level Model Showing Associations Between Infant Birth Weight, Interpregnancy Interval, and Diurnal Cortisol Slope Sampled Before and During Pregnancy: Fixed Effects With Robust Standard Errors and Additional Covariates (n = 142)

Fixed effects	Estimate	(SE)	t ratio	df	p
Cortisol intercept (morning)	1.67	0.06	28.66	136	<0.001
Level 2 covariates
Pregnancy trimester	0.22	0.03	7.55	251	<0.001
Level 3 covariates
Infants’ Birth Weight	0.03	0.04	0.65	136	0.518
Interpregnancy Interval	0.0001	0.0002	0.54	136	0.594
Household income	0.000004	0.000002	1.71	136	0.090
Cohabitation	−0.06	0.11	−0.51	136	0.612
African-American	−0.39	0.10	−3.73	136	0.001
Cortisol slope (time)	−0.08	0.00	−25.99	638	<0.001
Level 2 covariates
Pregnancy trimester	0.01	0.003	3.23	638	0.001
Level 3 covariates
Infants’ Birth Weight	−0.01	0.003	−3.05	638	0.002
Interpregnancy Interval	−0.00003	0.00001	−2.27	638	0.023
Household income	−0.000000	0.000000	−2.13	638	0.033
Cohabitation	−0.01	0.01	−0.78	638	0.434
African-American	0.07	0.007	10.62	638	<0.001
CAR	0.16	0.05	3.53	638	<0.001
Sample clarity	0.06	0.05	1.20	638	0.233

Notes. Pregnancy trimester coded as 0 for preconception study days, 1 for first trimester, 2 for second trimester, and 3 for third trimester. Interpregnancy interval calculated as difference between birth of index child and LMP. Sampling time is centered around wake time = 5 am. Household income is adjusted for cost of living differences across study site. Variable names for Level 1 indices (intercept, slope, CAR, and sample clarity) are presented in bold font.