Abstract
BackgroundResults of previous studies on the association between maternal haemoglobin concentration during pregnancy and stillbirth risk are inconclusive. It is not clear if haemoglobin concentration before pregnancy has a role. Using prospectively collected information from pre-pregnancy and antenatal visits, we investigated associations of maternal haemoglobin concentrations before and during pregnancy and haemoglobin dilution with stillbirth risk.MethodsIn a population-based case–control study from rural Golestan, a province in northern Iran, we identified 495 stillbirths (cases) and randomly selected 2,888 control live births among antenatal health-care visits between 2007 and 2009. Using logistic regression, we estimated associations of maternal haemoglobin concentrations, haemoglobin dilution at different stages of pregnancy, with stillbirth risk.ResultsCompared with normal maternal haemoglobin concentration (110–120 g/l) at the end of the second trimester, high maternal haemoglobin concentration (≥140 g/l) was associated with a more than two-fold increased stillbirth risk (OR = 2.31, 95 % CI [1.30–4.10]), while low maternal haemoglobin concentration (<110 g/l) was associated with a 37 % reduction in stillbirth risk. Haemoglobin concentration before pregnancy was not associated with stillbirth risk. Decreased haemoglobin concentration, as measured during pregnancy (OR = 0.61, 95 % CI [0.46, 0.80]), or only during the second trimester (OR = 0.75, 95 % CI [0.62, 0.90]), were associated with reduced stillbirth risk. The associations were essentially similar for preterm and term stillbirths.ConclusionsHaemoglobin concentration before pregnancy is not associated with stillbirth risk. High haemoglobin level and absence of haemoglobin dilution during pregnancy could be considered as indicators of a high-risk pregnancy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12884-016-0924-x) contains supplementary material, which is available to authorized users.
Highlights
Results of previous studies on the association between maternal haemoglobin concentration during pregnancy and stillbirth risk are inconclusive
Maternal haemoglobin concentration measured before pregnancy was not associated with stillbirth risk
We estimated associations between the maternal haemoglobin concentrations and risk of stillbirth stratified by gestational age, which showed no notable differences in the results (Additional file 1)
Summary
Results of previous studies on the association between maternal haemoglobin concentration during pregnancy and stillbirth risk are inconclusive. It is not clear if haemoglobin concentration before pregnancy has a role. There is significant change in maternal haemostatic profile [7], including haemoglobin dilution due to the expanding serum component of the blood [8]. Disruption in this process, possibly due to pathology in early pregnancy [9], seems to be associated with adverse pregnancy outcomes [2]. In the rural part of the province, most pregnancies are planned
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