Angiogenic Serum Biomarker Levels Are Related to Onset of Labour in Low-Risk Term and Post-Term Pregnancies: A Prospective Observational Cohort Study.

OBJECTIVE

To investigate whether angiogenic biomarkers at term in low-risk pregnancies are associated with the timing of spontaneous and induced labour, and to assess changes from term to post-term gestation.

DESIGN

Prospective, non-interventional, observational cohort study.

SETTING

Single tertiary care centre, Switzerland.

POPULATION: Low-risk term and post-term pregnancies.

METHODS

Soluble fms-like tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF) were measured and time intervals from sampling to delivery were analysed in spontaneous (n = 136) and induced labour (n = 48).

MAIN OUTCOME MEASURES: Time to spontaneous labour onset and delivery; induction-to-delivery intervals; biomarker changes from term to post-term.

RESULTS

In spontaneous labour, higher sFlt-1 levels and sFlt-1/PlGF ratios were inversely correlated with time to delivery (both p = 0.03). The sFlt-1/PlGF ratio remained independently associated with shorter time to delivery after adjustment for gestational age, maternal body mass index, and parity. In induced labour, higher PlGF levels were associated with longer induction-to-delivery intervals (p = 0.02). From term to post-term, PlGF declined (median 208 vs. 148 pg/mL, p < 0.0001), whereas sFlt-1 (median 3128 vs. 3631 pg/mL) and the sFlt-1/PlGF ratio (14 vs. 24) increased (both p < 0.0001).

CONCLUSIONS

In low-risk term pregnancies, an anti-angiogenic profile is associated with shorter time to spontaneous delivery and increases from term to post-term consistent with physiological placental maturation. In induced labour, biomarkers reflect placental state but do not independently predict induction dynamics. Their potential role in late-term risk assessment warrants further investigation.