Obstetrics & Gynaecology Calculators

35 calculators & risk scores

Browse 35 Obstetrics & Gynaecology clinical calculators and risk scores used in everyday UK practice. Every tool runs entirely in your browser — enter the values and get instant scoring, colour-coded interpretation bands and a link to the underlying guideline or publication. ClinCalc Pro is free, needs no sign-up, and is built for working clinicians.

These obstetrics & gynaecology tools span Labour & Delivery, Antenatal, VTE Prevention, Maternal Deterioration, Fetal Growth, Hypertensive Disorders and more.

Bishop Score

Bishop score (1964) of cervical readiness for induction of labour. NICE NG207: 6 or less → cervical ripening methods; more than 6 → amniotomy and oxytocin; 8 or more generally indicates a ripe cervix.
Gestational Age & Milestones

Interprets gestational age in weeks to identify viability, anomaly scan, and term thresholds.
Pre-eclampsia Risk Assessment

NICE-based risk factor assessment for pre-eclampsia to guide aspirin prophylaxis from 12 weeks.
VTE Risk in Pregnancy (RCOG)

RCOG Green-top Guideline 37a antenatal VTE risk score (Appendix III), at booking and on any admission. Reassess at delivery with the postnatal factors (caesarean, PPH, prolonged labour, preterm birth, stillbirth).
Modified Obstetric Early Warning Score (MEOWS)

Modified early obstetric warning system (CEMACH 2007; validated by Singh 2012): a trigger is one red or two yellow parameters.
Estimated Fetal Weight (Hadlock)

Estimates fetal weight from ultrasound measurements using Hadlock 4-parameter formula.
VBAC Success Probability (MFMU, Grobman 2021)

Predicted chance of vaginal birth after caesarean for a trial of labour at term after one previous low-transverse caesarean (MFMU model without race or ethnicity, Grobman 2021), from information available at the first antenatal visit.
HELLP Syndrome Diagnostic Criteria

Mississippi triple-class system for HELLP syndrome (Martin 1999): LDH ≥ 600 IU/L with platelet and transaminase thresholds. Class 1 is the most severe.
Ectopic Pregnancy & β-hCG Discriminatory Zone

Risk stratification for ectopic pregnancy based on β-hCG level, USS findings, and clinical features.
Edinburgh Postnatal Depression Scale (EPDS)

10-item validated screening tool for postnatal depression. Validated for antenatal use. Score ≥13 suggests probable depression.
Fetal Biophysical Profile (BPP) Score

5-component ultrasound-based assessment of fetal wellbeing. Each component scores 0 or 2. Total 0–10. Used for fetal surveillance in high-risk pregnancies. Score ≤6 may indicate fetal compromise.
IOTA Simple Rules for Ovarian Mass Classification

IOTA simple rules classify an adnexal mass as benign (B-features only), malignant (M-features only) or inconclusive (both or neither). Prospectively the rules applied to 76% of masses, with sensitivity 95% and specificity 91% (Timmerman 2008).
Risk of Malignancy Index (RMI) for Ovarian Cancer

Combines ultrasound score (U), menopausal status (M), and serum CA-125 to calculate RMI. RMI >200 = high risk of ovarian malignancy; refer to specialist cancer centre. Validated in UK NHS setting (RCOG guideline).
Abuse Assessment Screen (AAS)

5-item validated screen for physical, sexual, and emotional abuse in pregnancy and reproductive health settings. Any positive response requires further assessment and safety planning.
Modified Bishop Score for Cervical Ripeness

Cervical readiness for induction scored with Bishop's five items (dilatation, effacement, station, consistency, position; 0–13). Modified Bishop scores replace effacement with cervical length or add obstetric adjustments and are scored differently. NICE NG207: 6 or less → ripening; more than 6 → amniotomy and oxytocin.
Rh(D) Immune Globulin Dosage for Maternal-Fetal Haemorrhage

Calculates appropriate dose of Rh(D) immune globulin (anti-D) after maternal-fetal haemorrhage in Rh(D)-negative women. Based on Kleihauer-Betke test result. Prevents Rh sensitisation.
Modified Finnegan Neonatal Abstinence Score (NAS)

Assesses severity of neonatal abstinence syndrome (NAS) in neonates exposed to opioids in utero. 21 signs scored at regular intervals. Total ≥8 for 3 consecutive scores suggests pharmacological treatment needed.
Reid's Colposcopic Index (RCI)

Colposcopy scoring tool assessing the severity of cervical lesions based on 4 signs seen at colposcopy. Correlates with cervical intraepithelial neoplasia (CIN) grade. Score 0–8: low score = CIN 1; high score = CIN 2/3.
Swede Score for Colposcopy

5-item colposcopic score (aceto uptake, margins/surface, vessels, lesion size, iodine staining; each 0–2, total 0–10) for predicting high-grade CIN (CIN 2+). Score ≥ 8 = high-grade lesion likely; 0–4 = low risk.
YEARS Algorithm for Pulmonary Embolism

Validated algorithm combining 3 clinical criteria with D-dimer threshold to safely exclude pulmonary embolism. Particularly validated in pregnancy (adapted YEARS). Reduces CT-PA use vs. Wells score.
FIGO Staging for Ovarian Cancer (2014)

2014 FIGO (International Federation of Gynaecology and Obstetrics) staging system for ovarian, fallopian tube, and peritoneal cancer. Used for prognosis and treatment planning.
Pre-eclampsia Risk Screening (NICE NG133)

NICE NG133 pre-eclampsia risk factors: any high-risk factor, or more than one moderate-risk factor, indicates aspirin from 12 weeks.
Bishop Score (Cervical Ripeness for Induction)

Bishop score of cervical readiness for induction of labour. NICE NG207: 6 or less → cervical ripening methods; more than 6 → amniotomy and oxytocin; 8 or more generally indicates a ripe cervix.
Risk of Malignancy Index (RMI) for Ovarian Mass

Predicts ovarian malignancy probability from USS features, menopausal status, and CA-125. RMI >= 200 warrants specialist referral.
Estimated Date of Delivery (Naegele Rule)

Calculates weeks remaining to EDD from last menstrual period using the Naegele rule (LMP + 280 days).
Cervical Cerclage Criteria (Short Cervix / Preterm Risk)

Identifies women at risk of preterm birth who may benefit from cervical cerclage or vaginal progesterone.
FIGO Cervical Cancer Staging (2018)

Stages cervical cancer using 2018 FIGO classification to guide treatment selection (surgery vs chemoradiotherapy).
PID Diagnosis and Hospitalisation (CDC Criteria)

CDC 2021: presumptive PID treatment when at least one minimum criterion (cervical motion, uterine or adnexal tenderness) is present; hospitalisation criteria include tubo-ovarian abscess and severe illness.
Placenta Praevia / Accreta Risk Assessment

Assesses risk of placenta praevia and placenta accreta spectrum (PAS) disorder. Guides third trimester USS and surgical planning.
Biophysical Profile (BPP) Score

Five-component fetal wellbeing assessment (Manning 1980): NST, fetal breathing, gross body movement, tone, and amniotic fluid volume. Each scored 0 or 2. Total 0–10. Used in third-trimester surveillance for high-risk pregnancies.
MOEWS — Modified Obstetric Early Warning Score

Modified obstetric early warning system (MEOWS/MOEWS; CEMACH 2007, validated by Singh 2012): a trigger is one red or two yellow parameters.
Robson 10-Group Caesarean Section Classification

WHO-endorsed (2015) standardised classification of caesarean populations based on parity, labour onset, gestation, and presentation (Robson 2001). Used for audit and inter-unit comparison rather than individual decision-making.
VBAC Success — Grobman MFMU Calculator (Bands)

Predicts likelihood of successful vaginal birth after caesarean (TOLAC) using maternal age, BMI, prior vaginal delivery, prior VBAC, and indication for prior CS (Grobman 2007; race-free recalibration 2021). Use the live MFMU online tool for individualised %; this calculator records the band.
LEFt Rule for DVT in Pregnancy

Three-variable rule for DVT in pregnancy (Chan 2009): symptoms in the Left leg, ≥2 cm calf circumference difference (Edema), and First-trimester presentation. Score 0 has very low DVT prevalence; score ≥1 mandates duplex US.
YEARS-Adapted Algorithm for PE in Pregnancy

Pregnancy-adapted YEARS algorithm (van der Pol 2019, Artemis study). Three YEARS items + D-dimer threshold that varies with item count. Safely excludes PE in 39% without imaging.