Maternal hemoglobin concentrations across pregnancy and maternal and child health: a systematic review and meta‐analysis

Abstract

Maternal anemia is a well‐recognized global health problem; however, there remain questions on specific hemoglobin (Hb) thresholds that predict health risk or protection for mother and child. We conducted a systematic review and meta‐analysis to examine the associations of maternal Hb concentrations with a range of maternal and infant health outcomes, accounting for the timing of measurement (preconception, and first, second, and third trimesters), etiology of anemia, and cutoff category. The systematic review included 272 studies and the meta‐analysis included 95 studies. Low maternal Hb (<110 g/L) was associated with poor birth outcomes (low birth weight, preterm birth, small‐for‐gestational‐age (SGA), stillbirth, and perinatal and neonatal mortality) and adverse maternal outcomes (postpartum hemorrhage, preeclampsia, and blood transfusion). High maternal Hb (>130 g/L) was associated with increased odds of SGA, stillbirth, preeclampsia, and gestational diabetes. Relationships varied by the timing of measurement and cutoff category (stronger associations with lower cutoffs); limited data were available on anemia etiology. There were insufficient data for other maternal outcomes and long‐term child health outcomes. Current data are insufficient for determining if revisions to current Hb cutoffs are required. Pooled high‐quality individual‐level data analyses, as well as prospective cohort studies, would be valuable to inform the reevaluation of Hb cutoffs.

The contribution of iron deficiency to the risk of peripartum transfusion: a retrospective case control study

“…Given iron's critical role in DNA synthesis and cellular metabolism [10], it is not surprising that it also plays a crucial role in fetal development. In fact, maternal IDA increases the risk of prematurity [11,12], fetal intrauterine growth restriction [11,13], developmental delay [14] and perinatal mortality [12,13]. The risks associated with anemia in pregnancy correlate best with hemoglobin levels tested in the first trimester, prior to significant plasma expansion [15].…”

Haemoglobin levels in early pregnancy and severe maternal morbidity: population‐based cohort study

“…11 Published studies on maternal haemoglobin concentration and maternal morbidity were largely completed in low-and middle-income regions, or in high-income countries without universal access to prenatal care. 11,12 These studies also generally lacked details about important confounders, such as chronic maternal conditions, body mass index (BMI), supplemental iron use and other indicators of iron status, including serum ferritin and mean red blood corpuscular volume (MCV). Finally, completed studies have focused on just a few maternal outcomes, such as red blood cell (RBC) transfusion, placental abruption and postpartum haemorrhage.…”

“…Finally, completed studies have focused on just a few maternal outcomes, such as red blood cell (RBC) transfusion, placental abruption and postpartum haemorrhage. 11,12 Severe maternal morbidity (SMM) offers a practical and validated proxy for maternal death (or 'near miss') and prolonged hospital length of stay, and it can be ascertained using population-based healthcare administrative data. [12][13][14][15][16] The SMM composite comprises about 40 morbidity measures arising in pregnancy, during labour or postpartum, 17 with an exponential rise in mortality as the number of SMM indicators increases.…”

The impact of iron deficiency correction in pregnant women on the perinatal period and children’s health status

“…Однако авторы отмечают, что при изучении в группах, составленных с учетом социально-экономического уровня страны, в которой проводилось исследование, наибольшая корреляция обнаружена в странах с низким и средним уровнем экономического развития. Большое значение имеют степень снижения уровня гемоглобина и сроки манифестации анемии: наибольшее негативное влияние ассоциировано с уровнем гемоглобина <70 г/л и анемией, возникшей в преконцептуальном периоде [12]. В нашем исследовании разницы по частоте развития преэклампсии не обнаружено (р=0,569), что, вероятно, объясняется легкой степенью тяжести анемии и проведенным лечением.…”

“…[11] обнаружил связь неблагополучного течения и исходов беременности не только с низким, но и с высоким уровнем гемоглобина, причем эта особенность наиболее характерна для экономически развитых стран. В связи с этим большой интерес представляют результаты другого метаанализа, которые показали ассоциацию частоты мертворождений с уровнем гемоглобина ≥140 г/л, превышающим «норму беременности» [12]. Вероятно, необходимо рассматривать уровень гемоглобина как непрерывный параметр, влияющий на течение беременности за счет, например, повышения вязкости крови, нарушения трансплацентраного транспорта кислорода и питательных веществ, а также изменения физиологической гиперволемии во II-III триместре беременности [10][11][12].…”