Maternal haemoglobin concentration and risk of preterm birth in a Chinese population

Abstract

The aim was to examine the relationship between maternal haemoglobin (Hb) concentrations and risk of preterm birth by secondary analysis of data from a randomised controlled trial. This analysis included 10,430 women who were at least 20 years old and no more than 20 weeks of gestation. Results revealed neither first- nor second-trimester Hb concentrations were associated with the risk of preterm births. However, the risk of preterm birth increased when the Hb level was low (<130 g/L) in the first but high (≥130 g/L) in the second trimester, regardless of supplement type (iron-containing: AOR: 2.26, 95% CI: 1.37–3.73; non-iron-containing: AOR: 2.16, 95% CI: 1.11–4.21). In conclusion, maternal Hb concentrations were not associated with the risk of preterm birth. A low-Hb level in the first trimester but coupled with a high Hb level in the second was associated with an elevated risk of preterm birth.

Impact statement

• What is already known on this subject: The relationship between maternal Hb concentration and preterm birth remains inconclusive. Some studies have shown an association between a low- or a high-Hb level and an increased risk of preterm birth. Others have not found such an association. Yet others have shown a U-shaped relationship.

• What do the results of this study add: Overall, maternal Hb concentrations in first or second trimester were not statistically associated with the risk of preterm birth. However, women with a low Hb concentration in the first trimester together with a high Hb concentration in the second trimester had an increased risk of preterm birth, compared to women who had a higher Hb concentration in the first trimester that remained similar during the second trimester.

• What are the implications are of these findings for clinical practice and/or further research: Our finding helps identify mothers who are at risk of having a preterm delivery. Investigating the underlying clinical causes of the unfavourable change in Hb levels and close follow-up to these women may help improve birth outcomes.

Keywords:

• Haemoglobin
• preterm birth
• iron
• pregnancy
• anaemia

Acknowledgments

We are grateful to all study participants and the local health care workers from Yuanshi, Mancheng, Xianghe, Fengrun and Laoting counties in China.

Disclosure statement

The authors declare no conflicts of interest and we have no financial relationship with the organisation that sponsored the research. The authors have had full control of all primary data and we agree to allow the Journal to review our data if requested.

Additional information

Funding

The original study was supported by a cooperative agreement between Peking University Health Science Center and the Centers for Disease Control and Prevention (5U01DD000293).