TABLE 3.

Associations of a low or high hemoglobin concentration in the third trimester with birth outcomes¹

				Low hemoglobin2				High hemoglobin2
Study (ref), year	Hemoglobin cutoffs	n	Country or study type	LBW	PTB	SGA	Stillbirth	LBW	PTB	SGA	Stillbirth
Alwan et al. (21), 2015	<105 g/L	362	England		(↓)	o
Chang et al. (5), 2003	≤95, >120 g/L	918	United States	o	↑	o		↑	↑	o
Hämäläinen et al. (11), 2003	<100 g/L	597 cases, 22,202 controls	Finland	o	o	o	o
Hwang et al. (26), 2010	<100 g/L	377 cases, 3183 controls	Korean		↑	↑
Maghsoudlou et al. (12), 2016	<110, ≥140 g/L	495 cases, 2888 controls	Iran				↓				↑
Mohamed et al. (27), 2012	<110, ≥120 g/L	17,338	United States	↑	↑			↓	↓
Scanlon et al. (14), 2000	<−1, >1 SD from the reference group	173,031	United States		o	↓			o	o
Scholl and Hediger (28), 1994	<110 g/L	755	United States	o	o
Verhoeff et al. (24), 2001	<80 g/L	1423	Malawi		o	o
Xiong et al. (25), 2000	<100–110 g/L	NA	Meta-analysis	(↓)	(↓)	o
Zhang et al. (17), 2009	<100, ≥120 g/L	160,700	China		↓				o
Zhang et al. (18), 2009	<100, ≥120 g/L	1354 cases, 163,313 controls	China				↓				↑
Zhou et al. (19), 1998	<100, ≥120 g/L	829	China	o	o	o		o	o	o

¹↑ indicates a positive association (higher OR or RR of birth outcome), P < 0.05; (↑) indicates a marginally significant positive association, 0.05 ≥ P < 0.10; ↓ indicates a negative association (lower OR or RR for birth outcome), P < 0.05; (↓) indicates a marginally significant negative association, 0.05 ≥ P < 0.10; o indicates no association; a blank cell indicates the relation was not examined. LBW, low birth weight; NA, not applicable; PTB, preterm birth; ref, reference; SGA, small-for-gestational-age.

²Low and high hemoglobin concentrations as defined by each study. Cutoffs used for each definition are provided in the second column.