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Effect of iron supplementation during early pregnancy on the development of gestational hypertension and pre-eclampsia



To investigate the association between iron supplementation during early pregnancy and the presence of de novo hypertension after 20 weeks’ gestation (either gestational hypertension or pre-eclampsia).

Study design

Retrospective cohort study.


This study retrospectively reviewed the medical records of non-anemic pregnant women who received first antenatal care at the Department of Obstetrics and Gynecology, Faculty of Medicine Vajira Hospital, Navamindradhiraj University, Bangkok, Thailand, during the June 2009–December 2010 study period. All included women had blood pressure and urine albumin level data that were recorded at each antenatal visit. The study population was divided into one of the two following groups: iron supplementation starting at gestational age (GA) < 16 weeks (study group) or GA ≥ 16 weeks (control group). A comparison of the proportion of de novo hypertension arising after 20 weeks’ gestation was then performed between groups.


Four hundred non-anemic pregnant women were included, with 200 patients allocated to each groups. The overall incidence of de novo hypertension after 20 weeks’ gestation was 10% (40/400), with significantly higher prevalence in the study group than that in the control group [13.5% (27/200) vs. 6.5% (13/200); relative risk: 2.14, 95%, CI 1.22–3.73; p = 0.008]. None of the women in this study developed anemia at time of delivery. There was no significant difference between groups for GA at delivery, birth weight, or birth asphyxia.


In our study population, iron supplementation before 16 weeks’ GA was significantly associated with increased risk of developing de novo hypertension after 20 weeks’ gestation.

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This was an unfunded study.

Author information

Authors and Affiliations



PJ: project development, data collection, data analysis, and manuscript writing. SS: project development, manuscript editing, and others (Supervisor). CR: project development and data analysis. KT: manuscript editing. BW: project development and data collection.

Corresponding author

Correspondence to Preeyaporn Jirakittidul.

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Conflict of interest

All the authors declare no personal or professional conflicts of interest, and no financial support from the companies that produce and/or distribute the drugs, devices, or materials described in this report.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the Hospital Institutional Review Board and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Statement of human rights

The present study was the retrospective study. All data were collected from previous hospital record.

Informed consent

For this type of study formal consent for participation is not required.

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Jirakittidul, P., Sirichotiyakul, S., Ruengorn, C. et al. Effect of iron supplementation during early pregnancy on the development of gestational hypertension and pre-eclampsia. Arch Gynecol Obstet 298, 545–550 (2018).

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  • Thai
  • Iron supplementation
  • Early pregnancy
  • Pre-eclampsia
  • Gestational hypertension