This calculator screens for well-documented risk factors for spontaneous preterm birth — a birth before 37 weeks — using a transparent, additive checklist rather than a single validated predictive score. It is built for expectant parents and clinicians who want a quick, educational overview of which known risk factors are present, sourced from ACOG's guidance on the prediction and prevention of spontaneous preterm birth. This article explains how the checklist is built, what each tier means, and where its limits lie.

Why there's no single 'preterm birth score'

Unlike the Bishop score for induction readiness or many other clinical instruments, there is no single, universally validated composite score that turns preterm-birth risk factors into an exact percentage. ACOG's Practice Bulletin on the prediction and prevention of spontaneous preterm birth names a set of risk factors individually associated with elevated risk, but it does not publish a combined point-total that predicts a specific probability for a given patient.

This calculator fills that gap responsibly: it lists ten named risk factors, tags each as 'major' (2 points) or 'minor' (1 point) by how strongly the literature associates it with spontaneous preterm birth, and sums the checked items into a transparent screening tier. The number is intentionally framed as 'screening points,' never a percentage.

What the three tiers mean

Average / Baseline Risk (0 points) means none of the ten listed factors are present. It is a genuinely reassuring baseline, but not proof against preterm birth — some preterm births happen with no identifiable risk factor at all, so ongoing prenatal care still matters.

Elevated Risk (1-3 points) reflects one or more risk factors, which could be a single major factor (like a prior preterm birth) or several minor ones. It's a signal worth raising at the next prenatal visit rather than an urgent flag on its own.

High Risk (4-13 points) is reached with combinations like two major factors, or one major factor plus multiple minors. This tier is where a focused conversation with the OB or maternal-fetal medicine (MFM) provider about surveillance (e.g. serial cervical-length ultrasounds) or prevention (e.g. progesterone, cerclage evaluation) commonly becomes relevant.

Limits and how it should be used

This checklist deliberately excludes race and ethnicity as a scored input. The literature documents real population-level disparities in preterm-birth rates, but that is not an individually actionable screening item for a self-checklist, and including it risks implying a determinism it doesn't have — so it is left out entirely rather than scored.

The ten factors here are not exhaustive. Socioeconomic stressors, periodontal disease, assisted-reproduction status, and other factors discussed in the literature are not included, and the checklist cannot replace a full prenatal history and physical exam. It is additive, not multiplicative — it does not model interactions between factors. This calculator is for education and clinical reference only and should never be the sole basis for a management decision; any concern for preterm labor requires immediate evaluation by the treating obstetric provider.