Recurrent Preterm Birth
Risk Calculator
Select both criteria — results update instantly on the right. No button needed.
Publication Used in This Tool
1
IPD Meta-Analysis · AJOG MFM 2026
van Dijk CE, de Ruigh AA, Gravesteijn BY, Kazemier BM, Berghella V, Owen J, et al. Patterns of recurrent preterm birth: an individual patient data meta-analysis. Am J Obstet Gynecol MFM. 2026;8:101927.
What this tool does: All risk percentages are observed rates from Table 3 of this publication — 1,316 untreated patients across 7 international cohorts, transvaginal cervical length measured 18–24 weeks. No extrapolation. No modeling. Every number is directly from the paper.
Gestational age — most recent prior spontaneous delivery
Select the most recent delivery, including term births. If most recent was at term, select "37+ wks."
Current cervical length — transvaginal ultrasound (18–24 wks gestation)
Measured by trained sonographer in the current pregnancy.
Results appear here instantly
Select gestational age and cervical length on the left. No calculate button needed.
Prior GA
+
Cervical Length
→ Live results
⚠ Small sample size in this cell — 95% confidence intervals are wide. Interpret the point estimate with caution.
Recurrence Risk by Gestational Age Threshold
PTB <32 wks
PTB <34 wks
PTB <37 wks
ReferenceNulliparous — no prior sPTB1.5%4.9–10.5%
Multiparous — no prior sPTB0.8%4.5–6.6%
Clinical Implications
Clinical decision support only. Observed rates from untreated international cohorts (data 2001–2008). No subgroup achieves population-level baseline risk. All patients with prior sPTB require counseling and surveillance regardless of stratum. Does not replace clinical judgment. Source: van Dijk et al. AJOG MFM 2026;8:101927.