TABLE 3.

Associations between placental Fe transport proteins and indicators of maternal Fe status

Maternal Fe status	Placental target	Correlation	P	Partial correlation	P	na
SF midgestation	TfR1 protein	−0.32	<0.01	−0.23	<0.05	96
sTfR midgestation	TfR1 protein	0.23	<0.05	0.09	0.39	96
sTfR midgestation	TfR1 mRNA	0.15	0.18	0.25	<0.05	78
sTfR delivery		0.20	<0.05	0.25	<0.05	105
EPO delivery		0.24	<0.01	0.29	<0.01	103
sTfR midgestation	FPN protein	0.27	<0.05	0.22	0.14	56
sTfR delivery		−0.23	0.09	−0.31	<0.05	56
EPO midgestation	LRP1 mRNA	−0.26	<0.05	−0.28	<0.05	61
EPO midgestation	HRG1 protein	−0.27	<0.05	−0.33	<0.01	71
EPO delivery		−0.19	0.11	−0.27	<0.05	68
Hepcidin midgestation	HRG1 mRNA	−0.28	<0.05	−0.31b	<0.05b	53
Hepcidin midgestation	TfR1 protein	−0.27	<0.01	−0.16	0.15	95

Associations between maternal Fe status indicators and placental protein variables were tested with Pearson’s correlation and partial correlation tests. Raw and partial correlations and respective P values are shown. Partial correlation tests controlled for placental weight, birth weight, gestational age at birth (wk), maternal gynecologic age at conception (yr), maternal pregnancy weight gain, maternal prepregnancy body mass index, and maternal race. All measures of maternal Fe status at midgestation were adjusted for the gestational age on the date of blood collection. EPO, erythropoietin; FPN, ferroportin. ^aCorresponds to the partial correlation tests. ^bIn models that included SF or hepcidin, we assessed the potential impact of inflammation by including serum IL-6, and only this association was significantly affected. When maternal midgestation serum IL-6 was included, the partial correlation of midgestation hepcidin with HRG1 mRNA was −0.29; P = 0.056; n = 53.