Maternal serum ferritin at 11- to 13-week gestation in spontaneous early preterm delivery

Is there a maternal blood biomarker that can predict spontaneous preterm birth prior to labour onset? A systematic review

INTRODUCTION

The ability to predict spontaneous preterm birth (sPTB) prior to labour onset is a challenge, and it is currently unclear which biomarker(s), may be potentially predictive of sPTB, and whether their predictive power has any utility. A systematic review was conducted to identify maternal blood biomarkers of sPTB.

METHODS

This study was conducted according to PRISMA protocol for systematic reviews. Four databases (MEDLINE, EMBASE, CINAHL, Scopus) were searched up to September 2021 using search terms: "preterm labor", "biomarker" and "blood OR serum OR plasma". Studies assessing blood biomarkers prior to labour onset against the outcome sPTB were eligible for inclusion. Risk of bias was assessed based on the Newcastle Ottawa scale. Increased odds of sPTB associated with maternal blood biomarkers, as reported by odds ratios (OR), or predictive scores were synthesized. This review was not prospectively registered.

RESULTS

Seventy-seven primary research articles met the inclusion criteria, reporting 278 unique markers significantly associated with and/or predictive of sPTB in at least one study. The most frequently investigated biomarkers were those measured during maternal serum screen tests for aneuploidy, or inflammatory cytokines, though no single biomarker was clearly predictive of sPTB based on the synthesized evidence. Immune and signaling pathways were enriched within the set of biomarkers and both at the level of protein and gene expression.

CONCLUSION

There is currently no known predictive biomarker for sPTB. Inflammatory and immune biomarkers show promise, but positive reporting bias limits the utility of results. The biomarkers identified may be more predictive in multi-marker models instead of as single predictors. Omics-style studies provide promising avenues for the identification of novel (and multiple) biomarkers. This will require larger studies with adequate power, with consideration of gestational age and the heterogeneity of sPTB to identify a set of biomarkers predictive of sPTB.

Maternal serum ferritin as a clinical tool at 34-36 weeks' gestation for distinguishing subgroups of fetal growth restriction

OBJECTIVE

To compare maternal ferritin levels across pregnancies with fetal growth restriction including SGA and IUGR compared to appropriate for gestational age (AGA).

METHODS

Three groups were enrolled: AGA, SGA (birth weight below 10th percentile for gestational age with no placental insufficiency findings), and IUGR (birth weight below 5th percentile for gestational age accompanied by abnormal umbilical artery Doppler waveforms and/or oligohydramnios). Maternal serum ferritin samples were obtained at gestational weeks 34 through 36, and delivery occurred at or beyond 36 weeks.

RESULTS

A total of 126 pregnancies with AGA (36%), SGA (40%), and IUGR (24%) were enrolled. The mean maternal serum ferritin level was higher in the IUGR group than in the AGA group (59 μg/l versus 32.5 μg/l, p < 0.001). A maternal serum ferritin cutoff of 48 μg/l was found to be optimal for distinguishing between IUGR and AGA with a sensitivity of 67.7%, specificity of 92%, PPV of 84%, NPV of 82%, diagnostic accuracy of 82.7%, LR + of 8 and LR- of 0.3, respectively.

CONCLUSION

Maternal serum ferritin levels differ in pregnancies with IUGR. The role of maternal serum ferritin measurements as a clinical tool for distinguishing different forms of fetal growth restriction warrants further investigation.

High maternal serum ferritin in early pregnancy and risk of spontaneous preterm birth

Previous studies have reported inconsistent associations between maternal serum ferritin concentrations and the risk of spontaneous preterm birth (sPTB). The aim of the present study was to examine the association between Fe biomarkers, including serum ferritin concentrations, and the risk of total ( 75th percentile ( ≥ 43 μg/l) (OR 1.49, 95% CI 1.06, 2.10) and >90th percentile ( ≥ 68 μg/l) (OR 1.92, 95% CI 1.25, 2.96). Increased odds of early and moderate-to-late sPTB were associated with ferritin levels >90th percentile (OR 2.50, 95% CI 1.32, 4.73) and >75th percentile (OR 1.56, 95% CI 1.03, 2.37), respectively. No association was found between the risk of sPTB and elevated sTfR levels or Fe deficiency. In conclusion, elevated maternal serum ferritin levels in early pregnancy are associated with an increased risk of sPTB from 34 weeks of gestation. The usefulness of early pregnancy ferritin levels in identifying women at risk of sPTB warrants further investigation.

First trimester screening can predict adverse pregnancy outcomes

There has been an increasing drive over the last two decades to push the detection of women at risk of adverse pregnancy outcomes into the first trimester. This has led to a plethora of techniques, risk assessments and biomarkers, both fascinating and bewildering in its breadth. Despite the vast amount of knowledge available, it is often difficult to determine what is practicable and valuable for clinical practice. This is especially true as earlier diagnosis does not necessarily equate to improved outcomes for mother and child. We suggest that, at least for preeclampsia, fetal growth restriction, spontaneous preterm birth and gestational diabetes, there are effective first trimester tests available to identify the women at risk of subsequently developing complications. Unfortunately, there are no currently reliable first trimester tests available for identifying women at risk of stillbirth. It is likely that this field will continue to develop over time, and we hope that new and better strategies will continue to emerge to target these clinically important pathologies.