Data Reveal Mid-Trimester CRP-to-Albumin Ratio Strongly Predicts Subsequent Preeclampsia: Study

Could a simple combination of two routine lab values during mid-pregnancy hold the key to preeclampsia risk prediction? Preeclampsia continues to challenge clinicians, as it’s a leading cause of maternal and fetal morbidity—but early, reliable predictive tools remain elusive.

Study Design: A Robust Retrospective Cohort

Researchers from Türkiye conducted a retrospective, single-center cohort study published in BMC Pregnancy and Childbirth, analyzing data from 3,399 singleton pregnancies. All participants had their C-reactive protein (CRP) and albumin measured at 20–24 weeks’ gestation, before any hypertensive complications were diagnosed. The main variable studied—the CRP-to-albumin ratio (CAR)—was evaluated for its ability to predict subsequent preeclampsia, gestational hypertension, or normotensive outcomes.

Key Findings: Nonlinear Link Between CAR and Preeclampsia

Women who later developed preeclampsia had significantly higher mid-trimester CAR values (median 1.26) than those with gestational hypertension (0.86) or normotensive pregnancies (0.73).

The risk of preeclampsia rose steeply with increasing CAR: for example, a CAR of 1.25 compared to 0.75 was associated with an 8-fold increase in adjusted odds for preeclampsia.

These results held up even after adjusting for maternal age, body mass index, parity, mode of conception, early blood pressure, and gestational age at sampling.

Importantly, the association between CAR and preeclampsia was nonlinear—risk accelerated at higher CAR values, rather than rising in a simple straight line.

Model Performance and Clinical Implications

Adding CAR to a basic clinical model (age, BMI, blood pressure, and basic demographics) dramatically improved discrimination for preeclampsia (AUC rose from 0.51 to 0.86 after internal validation). CAR outperformed individual CRP or albumin values and showed robust associations across multiple sensitivity analyses and matched subgroups.

However, several caveats matter for clinical translation:

The baseline clinical model used in this research was basic and lacked well-established risk factors (like history of preeclampsia or aspirin use).

The reported CAR values represent descriptive contrasts, not validated diagnostic cutoffs.

External, prospective validation is still needed before the CAR can be considered for routine screening.

Why Does This Matter to Clinicians?

CAR is calculated from tests already done in most prenatal clinics. If validated externally, it could represent a highly accessible and low-cost tool for stratifying preeclampsia risk in the second trimester—especially where advanced biomarkers aren’t widely available. For now, CAR should be viewed as a promising research marker that may complement, not replace, established preeclampsia screening.

Conclusion

This large cohort study shows a strong, nonlinear association between mid-trimester CAR and later preeclampsia—well beyond the predictive ability of routine clinical factors alone. While CAR is not ready for clinical decision-making, these data reinforce the search for simple, accessible biomarkers to improve early detection and intervention for preeclampsia.

Key points

CAR in mid-pregnancy is strongly associated with preeclampsia risk.

Risk of preeclampsia rises sharply with higher CAR values, in a nonlinear fashion.

Including CAR in risk models substantially improves discrimination over routine clinical variables.

CAR is not a validated clinical cutoff—external research is needed before use in screening.

Consider CAR a promising exploratory marker, especially where advanced testing is not feasible.

Citation:

Ayaydın Yılmaz Kİ, Baki Yıldırım S. Association between the mid-trimester C-reactive protein-to-albumin ratio and subsequent preeclampsia: a retrospective cohort study. BMC Pregnancy and Childbirth. 2026; In Press. https://doi.org/10.1186/s12884-026-10105-4