Table 3.

Association between maternal FT4 (gestational week median 12, range: 8–20 weeks) and productive vocabulary from the MacArthur–Bates Communicative Development Inventories (MB-CDI) in the offspring aged 12–36 months (models 3 and 4). The association between FT4 and the probability of producing words from the MB-CDI are estimated by conditional growth models, including effects of time (offspring age) and main effects of covariates. The outputs of the conditional growth models are reported as odds ratios (OR), standard error (SE), and 95% CI. Numbers represent complete cases included in the analyses. P-values <0.05 are significant and marked in bold.

	Girls				Boys
	OR	SE	95% CI	P	OR	SE	95% CI	P
FT4 (<20% vs >80% percentile)
Girls, n = 97
Boys, n =111
Intercept	1.00	0.00	1.00; 1.00	<0.001	1.00	0.00	1.00; 1.00	<0.001
Offspring age	10.88	0.02	10.56; 11.21	<0.001	10.69	0.01	10.44; 10.96	<0.001
FT4 (>80%)	1.26	0.15	0.95; 1.69	0.11	0.97	0.14	0.74; 1.28	0.83
Maternal age	0.88	0.17	0.64; 1.22	0.46	0.88	0.15	0.65; 1.19	0.40
Breastfeeding	1.14	0.13	0.88; 1.47	0.33	1.24	1.14	0.95; 1.62	0.12
Maternal education
Linear	1.37	0.15	1.02; 1.84	0.04	0.93	0.16	0.68; 1.26	0.63
Quadratic	1.18	0.14	0.89; 1.55	0.25	0.81	0.14	0.61; 1.07	0.14
Primi- and multi-parous	0.92	0.17	0.66; 1.28	0.61	0.85	0.16	0.62; 1.17	0.32
Pre-pregnancy BMI
<18.5	0.75	0.14	0.57; 0.99	0.045	1.08	0.15	0.80; 1.45	0.62
>25	1.16	0.14	0.88; 1.52	0.29	0.97	0.14	0.73; 1.27	0.80
Offspring age × FT4 (>80%)	0.77	0.03	0.72; 0.82	<0.001	0.90	0.03	0.84; 0.95	<0.001
FT4 (linear)
Girls, n = 277
Boys, n = 298
Intercept	1.00	0.00	1.00; 1.00	<0.001	1.00	0.00	1.00; 1.00	<0.001
Offspring age	15.90	0.04	14.65; 17.26	<0.001	8.59	0.04	7.99; 9.24	<0.001
FT4 (linear)	1.13	0.09	0.95; 1.34	0.18	0.89	0.09	0.74; 1.07	0.21
Maternal age	0.89	0.10	0.73; 1.08	0.22	0.77	0.10	0.64; 0.93	0.01
Breastfeeding	1.19	0.08	1.02; 1.40	0.03	1.22	0.08	1.04; 1.44	0.02
Maternal education ()
Linear	1.17	0.09	0.98; 1.40	0.08	1.02	0.09	0.85; 1.22	0.87
Quadratic	1.12	0.09	0.95; 1.33	0.19	0.86	0.09	0.73; 1.02	0.09
Primi- and multi-parous	0.77	0.10	0.63; 0.93	0.01	0.95	0.09	0.79; 1.14	0.58
Pre-pregnancy BMI	0.86	0.10	0.70; 1.05	0.14	1.10	0.09	0.92; 1.31	0.30
<18.5
>25	1.03	0.09	0.87; 1.21	0.77	0.96	0.09	0.81; 1.14	0.63
Offspring age × FT4 (linear)	0.60	0.05	0.55; 0.65	<0.001	1.13	0.04	1.05; 1.23	0.002

BMI, body mass index; FT4, free thyroxine.