Obstetric Calculators and Antenatal Assessment

The estimated date of delivery calculator applies the conventional Naegele approach, adding 280 days to the first day of the last menstrual period, while recognising that ACOG guidance supports ultrasound-based dating when it differs by a defined margin. The gestational age calculator converts weeks and days into the decimal and weeks-plus-days forms used in antenatal records.

The Hadlock four-parameter model estimates fetal weight from head and abdominal measurements and femur length; it is an estimate with an acknowledged margin of error. The biophysical profile scores fetal wellbeing from breathing, movement, tone, amniotic fluid volume, and the non-stress test.

The Bishop score grades cervical readiness for induction of labour from dilatation, effacement, station, consistency, and position. A higher score predicts a more favourable cervix for induction.

The preeclampsia criteria calculator applies the ACOG definition — new-onset hypertension after 20 weeks with proteinuria or end-organ dysfunction — and counts severe features. The HELLP criteria assess hemolysis, elevated liver enzymes, and low platelets. Magnesium sulfate dosing supports seizure prophylaxis in severe preeclampsia and eclampsia.

The obstetric estimated blood loss calculator supports quantification by the gravimetric method or the hematocrit-based method. The gestational weight gain tool applies the IOM 2009 recommendations stratified by pre-pregnancy BMI. The Edinburgh Postnatal Depression Scale screens for perinatal depression.

Because these tools are calibrated to specific gestational windows and populations, the gestational age range for which a tool was validated should always be confirmed before it is applied. The outputs inform management alongside clinical findings, laboratory results, and the woman's own circumstances.