Table 4.

The associations of haemoglobin levels up to 14 weeks of gestation with the risks of miscarriage stratified by BMI in the first trimester and maternal age at conception.

			Miscarriage		Adjusted Model *
Maternal Characteristics		No. of Participants	n	%	OR (95% CI)	p-Value	p for Interaction
BMI <25 Kg/m2		5376	252	4.7			0.13
	Haemoglobin level (g/L)
	<110	205	20	9.8	2.77 (1.66 to 4.62)	<0.001
	110–139	4883	207	4.2	1.00 (ref.)
	≥140	288	25	8.7	2.25 (1.40 to 3.61)	0.001
BMI ≥25 Kg/m2		3559	217	6.1
	Haemoglobin level (g/L)
	<110	125	8	6.4	1.33 (0.63 to 2.78)	0.45
	110–139	3176	186	5.9	1.00 (ref.)
	≥140	258	23	8.9	1.45 (0.88 to 2.39)	0.14
Maternal age ≤ 29 years		4187	175	4.2			0.55
	Haemoglobin level (g/L)
	<110	169	11	6.5	2.14 (1.05 to 4.34)	0.036
	110–139	3768	142	3.8	1.00 (ref.)
	≥140	250	22	8.8	2.40 (1.47 to 4.24)	0.002
Maternal age > 29 years		5266	345	6.6
	Haemoglobin level (g/L)
	<110	189	19	10.1	2.09 (1.24 to 3.52)	0.006
	110–139	4737	288	6.1	1.00 (ref.)
	≥140	340	38	11.2	1.56 (1.01 to 2.40)	0.044

BMI, body mass index; OR, odds ratio; CI, confidence interval. * Logistic regression model was adjusted for maternal age (≤29, >29 years; for BMI analysis), BMI (<25, ≥25 Kg/m²; for maternal age analysis), parity (nulliparous, parous), smoking (no, yes), and prior miscarriage (0, 1, ≥2).