GA Calculator

Estimates gestational age and expected due date from last menstrual period

Indication

id: lmp_weeks_ago; label: Weeks since LMP; type: number; min: 0; max: 45; step: 1
id: lmp_days_extra; label: Extra days beyond complete weeks; type: number; min: 0; max: 6; step: 1

function(score, vals) { var weeks = parseInt(vals.lmp_weeks_ago) || 0; var days = parseInt(vals.lmp_days_extra) || 0; var totalDays = weeks * 7 + days; var remainingDays = 280 - totalDays; var remainingWeeks = Math.floor(remainingDays / 7); var ga = weeks + 'w' + days + 'd'; var trimester = weeks < 14 ? 'First Trimester' : (weeks < 28 ? 'Second Trimester' : 'Third Trimester'); var color = weeks < 37 ? 'yellow' : (weeks < 42 ? 'green' : 'red'); var action = 'GA: ' + ga + '. ' + trimester + '. '; if (weeks < 24) action += 'Pre-viability. '; else if (weeks < 34) action += 'Antenatal corticosteroids if preterm delivery anticipated. '; else if (weeks < 37) action += 'Late preterm. Consider steroids if <37w and delivery anticipated in 7 days. '; else if (weeks <= 41) action += 'Term. '; else action += 'Post-term. Discuss induction. '; action += 'Approximately ' + remainingWeeks + ' weeks until EDD.'; return { risk: ga, tier: trimester, action: action, color: color }; }

First trimester US dating (±5-7 days) is most accurate — use to adjust EDD if discrepant from LMP by > 5 days
Viability generally considered at 23-24 weeks in most centers
Antenatal corticosteroids: betamethasone 12mg IM q24h x 2 doses (24-34 weeks) for fetal lung maturity