Table 3 Mediation analysis of weight gain on the relationship between pre-pregnancy BMI and GDM.

Group		n	a	SE(a)	Z_a	b	SE(b)	Z_b	Z_a × Z_b	CI of Z_a × Z_b
Regardless of fetal sex
BMI (kg/m²)	All	67777	−0.239	0.004	−59.75	−0.018	0.004	−4.50	268.88	0.00243	to	0.00618^*
	<18.5	7055	−0.186	0.044	−4.23	−0.004	0.018	−0.22	0.94	−0.00607	to	0.00777
	18.5–24.9	45880	−0.168	0.009	−18.67	−0.018	0.005	−3.60	67.20	0.00137	to	0.00473^*
	25.0–29.9	11894	−0.353	0.025	−14.12	−0.024	0.007	−3.43	48.41	0.00358	to	0.01359^*
	≥30.0	2948	−0.217	0.031	−7.00	−0.019	0.011	−1.73	12.09	−0.00055	to	0.00924
Carrying a male fetus
BMI (kg/m²)	All	34934	−0.230	0.005	−46.00	−0.018	0.005	−3.60	165.60	0.00188	to	0.00641^*
	<18.5	3546	−0.149	0.063	−2.37	0.010	0.025	0.40	−0.95	−0.01048	to	0.00644
	18.5–24.9	23720	−0.162	0.012	−13.50	−0.021	0.007	−3.00	40.50	0.00117	to	0.00574^*
	25.0–29.9	6183	−0.329	0.034	−9.68	−0.017	0.010	−1.70	16.45	−0.00085	to	0.01236
	≥30.0	1485	−0.170	0.042	−4.05	−0.020	0.016	−1.25	5.06	−0.00190	to	0.00970
Carrying a female fetus
BMI (kg/m²)	All	32835	−0.249	0.005	−49.80	−0.019	0.005	−3.80	189.24	0.00229	to	0.00718^*
	<18.5	3509	−0.223	0.062	−3.60	−0.022	0.028	−0.79	2.83	−0.00749	to	0.01910
	18.5–24.9	22154	−0.175	0.013	−13.46	−0.014	0.007	−2.00	26.92	0.00005	to	0.00493^*
	25.0–29.9	5710	−0.378	0.036	−10.50	−0.031	0.010	−3.10	32.55	0.00422	to	0.01977^*
	≥30.0	1462	−0.270	0.046	−5.87	−0.018	0.015	−1.20	7.04	−0.00306	to	0.01352

BMI body mass index, GDM gestational diabetes mellitus, CI confidence interval, SE standard error.
Sex determination was not performed in eight stillbirths. a = raw (unstandardized) regression coefficient for the association between BMI (X) and weight gain (M, mediator); b = raw coefficient for the association between weight gain (M, mediator) and GDM (Y) (X is also a predictor of Y). SE(a) = standard error of a; SE(b) = standard error of b. Z_a = a/SE(a), Z_b = b/SE(b). We used Z_a × Z_b to measure the size of the mediating effect. ^*Statistical significance of the mediating effect was defined as a CI that did not include zero.

Search