Table 3.

Factors influencing thyroid gland function during pregnancy.

Response variable	Gestational period	Predictor variable	B (slope)	Std. error	t	Stand. coefficient (β)	95% CI for B	P-value	VIF (1)	DW (2)	R 2 (%) (3)	ANOVA (4)
TSH	wk. 6–9	Intercept	3.792	0.501	7.566		2.806	=4.779		1.575	10.6	F(3, 278) = 11.0 P < 0.001
		Anti-TPO	0.003	0.001	4.005	0.228	0.002–0.005	<0.001	1.08
		βHCG	0.000	0.000	−3.735	−0.212	0.000–0.000	<0.001	1.24
		Estradiol	7.462E−5	0.000	2.259	0.129	0.000–0.000	=0.025	2.59
	mo. 6–9	Intercept	0.987	0.535	1.843		−0.068 to 2.042	=0.067		1.612	2.4	F(1, 225) = 5.4 P = 0.021
		Progesterone	0.007	0.003	2.331	0.154	0.001–0.013	=0.021
fT4	wk. 6–9	Intercept	18.024	0.358	50.277		17.318–18.730	<0.001		1.599	1.8	F(1, 280) = 5.1 P = 0.024
		Progesterone	−0.006	0.003	−2.268	−0.134	−0.011 to −0.001	=0.024
	mo. 6–9	Intercept	16.876	0.976	17.473		14.953–18.800	<0.001		1.686	13.6	F(2, 225) = 17.7 P < 0.001
		Progesterone	−0.023	0.005	−4.322	−0.269	−0.033 to 0.012	<0.001	1.00
		Anti-TPO	0.010	0.002	3.953	0.246	0.005–0.015	<0.001	1.00
fT3	wk. 6–9	Intercept	4.895	0.045	109.179		4.807–4.983	<0.001		1.745	2.6	F(1, 280) = 7.5 P = 0.007
		Anti-TPO	−0.001	0.000	−2.738	−0.162	−0.001 to 0.000	=0.007
	mo. 6–9	Intercept	4.443	0.209	21.231		4.031–4.856	<0.001		2.000	2.3	F(1, 225) = 5.3 P = 0.023
		Progesterone	−0.003	0.001	−2.291	−0.151	−0.005 to 0.000	=0.023
Prolactin	wk. 6–9	Intercept	586.698	144.331	4.065		302.578–870.819	<0.001		1.808	26.0	F(3, 278) = 32.6 P < 0.001
		Estradiol	0.089	0.026	3.440	0.287	0.038–0.140	<0.001	2.88
		Progesterone	4.092	1.518	2.697	0.226	1.105–7.080	=0.007	2.88
		Anti-TPO	−0.885	0.386	−2.291	−0.119	−1.646 to −0.125	=0.023	1.00
	mo. 6–9	Intercept	2777.394	899.877	3.086		1004.086–4550.702	=0.002		2.076	10.7	F(2, 224) = 13.4 P < 0.001
		Progesterone	23.506	5.082	4.625	0.305	13.491–33.520	<0.001	1.88
		Estradiol	−0.123	0.035	−3.532	−0.233	−0.192 to −0.054	<0.001	1.88

(1) VIF denominates the variance inflation factor (VIF = 1/(1 − R²)), which is a marker of collinearity. A value of 1 indicates no collinearity. Values up to 5 indicate moderate collinearity.

(2) DW denominates the result of the Durbin–Watson test, which should optimally be between 1.5 and 2.5.

(3) R² denominates the coefficient of multiple determination.

(4) ANOVA findings are reported in APA format: F (regression degrees of freedom, residual degree of freedom) = F-ratio.

TSH, thyroid-stimulating hormone; fT4, free thyroxine; fT3, free triiodothyronine.