Medical Disclosure

Last updated August 31, 2026

ObCalc is a clinical decision-support tool. Every calculator in ObCalc is intended for use by licensed healthcare professionals as a reference aid — it does not replace clinical judgment, independent verification, or individualized counseling with a patient. ObCalc is not intended for use by patients or the general public to make medical decisions. Formulas, reference ranges, and thresholds are drawn from published literature and clinical practice guidelines, but guidelines change, population-derived estimates may not apply to an individual patient, and every result should be interpreted in the context of the complete clinical picture, current institutional protocol, and the guidance in force at the time of use. Always confirm any dose, threshold, or recommendation against your institution's own protocols before acting on it.

Below is the disclosure shown for each of ObCalc's 28 calculators, organized the same way they're grouped in the app.

Obstetrics

Bishop Score

For clinical reference only. Induction decisions should incorporate gestational age, maternal and fetal status, and clinical judgment.

Estimated Due Date

Dates are calculated from a standard 280-day (40-week) gestation and standard timing of conception, ovulation, and embryo transfer relative to the last menstrual period. Screening windows are general references — local protocols and individual clinical circumstances take precedence.

Pregnancy Re-dating

Decision support only. Thresholds follow ACOG Committee Opinion 700 ("Methods for Estimating the Due Date"), keyed to the gestational-age window by LMP. Ultrasound dating is most accurate in the first trimester; correlate with measurement quality and the full clinical picture. Once the EDD is established it should not be changed on the basis of a later scan.

Pregnancy Weight Gain

Singleton recommendations are from IOM (2009). Twin recommendations are IOM (2009) total-gain targets (normal weight: 16.8–24.5 kg; overweight: 14.1–22.7 kg; obese: 11.3–19.1 kg); weekly rates are derived from those totals. IOM (2009) did not establish targets for underweight women with twins — this calculator applies the normal-weight twin range in that case. "Expected gain to date" assumes 0.5–2 kg (singleton) or 2–4 kg (twin) first-trimester gain followed by the IOM weekly rate thereafter; treat it as a rough guide, not a diagnostic threshold.

Urine Protein Creatinine Ratio (UPCR)

The urine protein-to-creatinine ratio is a screening tool for proteinuria. A 24-hour urine collection remains the gold standard for quantification. Interpret results in the clinical context.

VBAC Calculator

Predicted probability of vaginal birth after cesarean from the race- and ethnicity-free Grobman 2021 MFMU model (Am J Obstet Gynecol 2021;225:664.e1). The paper publishes coefficients rounded to three decimal places, so results may differ from the live MFMU calculator by up to ~0.4% — a precision difference the paper itself notes. The published model does not include the coefficient covariance matrix, so no 95% confidence interval is shown here. This is a decision-support tool and does not replace clinical judgment or individualized counselling.

Perinatology / MFM

CVR (CPAM Volume Ratio)

The CVR is a decision support tool for evaluating congenital pulmonary airway malformations (CPAM). Clinical management decisions should involve a maternal-fetal medicine specialist.

Extremely Preterm Birth Outcome

Outcome estimates describe groups of infants with similar characteristics, derived from NICHD Neonatal Research Network data (2006–2012, validated 2006–2016). They do not predict the outcome of any individual infant. "Actively Treated" describes infants who received intensive care; "All Infants" includes all live-born infants with the given characteristics. Ranges reflect the variability seen across 80% of hospitals (10th–90th percentile).

Fetal Biometry

Measurements are referenced against published normative data. Percentiles and z-scores are for clinical decision support only — interpret in context of the complete clinical picture and with appropriate fetal medicine expertise.

IUT Transfusion

Decision support only. Volumes are estimates from population formulas; clinical judgment, donor-unit characteristics, and fetal status govern the actual transfusion. EFW currency, donor Hct, and all defaults must be confirmed before use. Lidocaine 100 mg/kg requires institutional protocol verification. Sources: Mandelbrot & Giannina formulas per Rausch IUT Calculator; fetal Hgb reference per standard neonatal literature.

MCA Doppler

MCA PSV MoM values are a screening tool for fetal anemia. Values should be interpreted by a qualified maternal-fetal medicine specialist. MoM above 1.5 warrants further evaluation.

Neonatal Morbidity

These polynomial regression estimates of neonatal morbidity rates are derived from population-level data and are intended as counseling tools only. Individual outcomes may differ significantly. Clinical judgment must always be applied.

Ponderal Index

Ponderal index norms vary modestly with gestational age and population. This calculator uses commonly cited population-level cutoffs and is not a standalone diagnostic test for intrauterine growth restriction — interpret alongside gestational age, growth charts, and clinical context.

Insulin Dose Calculator (GDM)

Insulin dose estimates are based on weight-based protocols for gestational diabetes mellitus. These are starting dose calculations only. Individualized titration under the supervision of a qualified clinician is required. Do not initiate insulin therapy based solely on these estimates.

Life-Limiting Skeletal Dysplasia

A screening aid only — not diagnostic and does not identify a specific dysplasia. Predictive accuracy for a life-limiting condition rises when multiple parameters are positive. Enter measurements in matching units (mm for lengths, mm circumference for FL/AC/TC/cardiac). Refer to MFM/genetics for definitive evaluation.

Twin Discordance

Twin birth weight discordance is a clinical screening tool. Management decisions should involve a maternal-fetal medicine specialist.

Umbilical Artery Doppler

Umbilical artery Doppler reference ranges are intended for use in the surveillance of fetal well-being. Values should be interpreted by a qualified maternal-fetal medicine specialist in the context of the full clinical picture.

General

Anion Gap

For clinical reference only. Always correlate with complete history, physical examination, and arterial blood gas values.

APGAR Score

Score should be assigned by the clinician present at delivery. Repeat at 5 and 10 minutes if initial score is < 7.

BMI

BMI is a screening tool and does not directly measure body fat. Interpret results in the clinical context of the individual patient.

Maternal Sepsis Assistant

Clinical decision support only — not a substitute for clinical judgment. Confirm all antibiotic regimens against local antibiogram, patient allergies, renal function, and gestational age. qSOFA has low sensitivity in pregnancy; a negative score does not exclude sepsis. Source: SMFM Consult Series #67 (AJOG 2023, DOI 10.1016/j.ajog.2023.05.019).

CMQCC Sepsis Screen

Screening and decision-support aid only — not a substitute for clinical judgment. Pregnancy-adjusted criteria apply ≥ 20 weeks gestation and ≤ 72 hours postpartum; otherwise use standard non-pregnancy screen criteria. A bedside evaluation must rule out alternative diagnoses (e.g., hemorrhage, preeclampsia) before acting. Source: CMQCC Obstetric Serious Infection / Sepsis Evaluation Flow Chart v6.14.24 (PMC11568914).

Gestational Age

Performs date arithmetic only, projecting a gestational age you provide onto another date. It carries no independent clinical interpretation — the accuracy of any result depends entirely on the accuracy and dating method of the gestational age you enter.

Iron Deficit

This calculator estimates iron deficit using the Ganzoni formula. Dosing decisions should be made in conjunction with clinical assessment and institutional protocols.

Peak Flow

This calculator estimates predicted peak expiratory flow rate (PEFR) based on height and age. It is a reference tool and does not replace direct spirometric measurement.

Thrombophilia

VTE Anticoagulation Dosing

Clinical decision support only — not a substitute for clinical judgment. Dose levels represent regimens, not milligram values; always confirm against institutional protocol, renal function, platelet count, body weight, and lactation status. Applies to inherited thrombophilias in pregnancy only. Acquired thrombophilia (e.g., antiphospholipid syndrome) is out of scope. Source: ACOG Practice Bulletin 196.

Genetics

cfDNA PPV/NPV

This calculator is a decision support tool. It is not a substitute for clinical judgment.

Nuchal Translucency

NT percentile uses the Chung (2004) normal reference (median = 0.437 + 0.01969 × CRL mm, SD 0.558) and is valid for CRL 40–85 mm (≈11–14 weeks). An enlarged NT is a screening finding, not diagnostic. Correlate with image quality, CRL dating, aneuploidy screening, and the full anatomic survey.

Questions About a Specific Tool

If you believe a formula, reference range, or citation is out of date or incorrect, please tell us — see Support. Accuracy reports from clinicians directly shape which fixes we prioritize.