Maternal haemoglobin concentrations before and during pregnancy and stillbirth risk: a population-based case-control study.
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. 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.



In 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.



Compared 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.



Haemoglobin 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.
Clinical Epidemiology Unit, Department of Medicine Solna, Karolinska Institute, Karolinska Hospital, SE-171 76, Stockholm, Sweden. Siavash.Maghsoudlou@ki.se.|Faculty of Medicine, Golestan University of Medical Sciences, Gorgan, Iran. Siavash.Maghsoudlou@ki.se.
Siavash
S
Maghsoudlou
Clinical Epidemiology Unit, Department of Medicine Solna, Karolinska Institute, Karolinska Hospital, SE-171 76, Stockholm, Sweden.
Sven
S
Cnattingius
Clinical Epidemiology Unit, Department of Medicine Solna, Karolinska Institute, Karolinska Hospital, SE-171 76, Stockholm, Sweden.|Division of Obstetrics and Gynecology, Department of Women's and Children's Health, Karolinska University Hospital and Institute, Stockholm, Sweden.
Olof
O
Stephansson
Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran.
Mohsen
M
Aarabi
Faculty of Medicine, Golestan University of Medical Sciences, Gorgan, Iran.
Shahriar
S
Semnani
Clinical Epidemiology Unit, Department of Medicine Solna, Karolinska Institute, Karolinska Hospital, SE-171 76, Stockholm, Sweden.|Clinical Epidemiology and Biostatistics, School of Medical Sciences, Örebro University, Örebro, Sweden.|Research Department of Epidemiology and Public Health, University College London, London, UK.
Scott M
SM
Montgomery
Faculty of Medicine, Golestan University of Medical Sciences, Gorgan, Iran.|Clinical Epidemiology Unit & Center for Pharmacoepidemiology, Department of Medicine, Karolinska Institute, Solna, Sweden.
Shahram
S
Bahmanyar
D000328:Adult; D016022:Case-Control Studies; D005260:Female; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D007492:Iran; D016015:Logistic Models; D011247:Pregnancy; D011262:Pregnancy Trimester, Second / Q000097:blood*; D018566:Pregnancy, High-Risk / Q000097:blood*; D011295:Prenatal Care / Q000706:statistics & numerical data; D012307:Risk Factors; D050497:Stillbirth
D006454:Hemoglobins
Adverse pregnancy outcome; Haemoglobin concentration; Haemoglobin dilution; Maternal anaemia; Stillbirth