Pregnancy · Timing
Pregnancy Due Date Countdown
Days, weeks, and percentage to your estimated due date. Only ~5% of babies are born on the exact EDD; 80% within 1 week. NICE NG207 supports induction offer at 41+0 weeks.
Last reviewed 2 June 2026
Don't know it yet? Use the Due Date Calculator first.
How accurate is EDD?
Only ~5% of babies born on exact EDD. ~80% within 1 week before/after. Normal term: 37-42 weeks. EDD = estimate.
How EDD is calculated
- Naegele’s rule: LMP + 280 days.
- First-trimester ultrasound: most accurate (±5 days).
- IVF: based on embryo transfer date.
Term categories
- Preterm: <37 weeks.
- Early term: 37-38+6.
- Full term: 39-40+6.
- Late term: 41-41+6.
- Post-term: ≥42+0 (induction usually before).
Past 40 weeks
- Membrane sweep offered 40-41 wk.
- Induction discussion 41+0 wk per NICE NG207.
- ~10% reach 42 weeks without intervention.
- Alternative: expectant + twice-weekly monitoring.
Signs labour is starting
- Progressive contractions (stronger, closer, longer).
- Backache.
- Pelvic pressure.
- “Show” (mucus plug).
- Waters breaking.
At term: 5-1-1 rule (5 min, 1 min, 1 hour) = hospital.
Trimesters
- T1: weeks 1-12.
- T2: weeks 13-27.
- T3: weeks 28-birth.
When telling people
Personal choice. Some give a 2-week window or guess month to manage expectations + reduce late-pregnancy messages.
Different scenarios
Scenario 1: 40+5 weeks, no signs of labour
Sweep offered; induction discussion at next visit. Twice-weekly monitoring if expectant.
Scenario 2: 38 weeks, contractions every 5 min for 1h
5-1-1 met. Call maternity unit / head in.
Scenario 3: 36 weeks, regular contractions starting
Possible preterm labour. Hospital same day. /calculators/cervical-length.
Scenario 4: Dates uncertain, 12-wk scan adjusts EDD by 6 days
Use scan-based EDD going forward.
Scenario 5: 41+3 weeks, declining induction
Expectant management with twice-weekly CTG + scans. Discuss risks + benefits.
Care guidance
- EDD is estimate; ranges normal.
- Most babies arrive within 2 weeks of EDD.
- Induction discussion ~41 wk.
- 5-1-1 = hospital at term.
- Tell people a window not exact date if helpful.
Sources
- NICE NG207. Inducing labour.
- NICE NG201. Antenatal care.
- RCOG. Estimating due date.
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Frequently asked questions
How is the countdown calculated?
From your ESTIMATED DUE DATE (EDD), we count days remaining to today + express as weeks + days. Also derive how far along by counting forward from implied last-period date (EDD - 280 days), showing percentage of 280-day pregnancy completed.
How accurate is my due date?
ONLY ~5% babies born on actual EDD. ~80% within 1 week before or after. NORMAL TERM: 37-42 weeks. EDD = ESTIMATE not deadline. Dating ultrasound (first-trimester crown-rump length, 11-13+6 wk) most accurate (~±5 days). LMP-based (Naegele's): assumes 28-day cycle + ovulation day 14; if cycles irregular or ovulation later, EDD adjusted.
How is due date calculated?
NAEGELE'S RULE: LMP + 280 days (40 weeks). Alternative: LMP + 7 days - 3 months + 1 year. ULTRASOUND DATING (most accurate): CRL at 11-13+6 weeks gives EDD ±5 days. NHS UK: scan EDD usually accepted; LMP if no scan or scan close to LMP-based EDD. IVF: based on embryo transfer date (different formula). /calculators/due-date /calculators/ivf-due-date.
When does pregnancy 'officially' end?
(1) FULL TERM: 39-40+6 weeks; (2) EARLY TERM: 37-38+6 weeks; (3) LATE TERM: 41-41+6 weeks; (4) POST-TERM: 42+0 weeks (induction usually offered before this); (5) PRETERM: <37 weeks. UK NICE NG207: routine induction usually OFFERED at 41+0 weeks (or 39+0 if maternal age 40+); not forced. INFORMED CHOICE.
What weeks am I 'overdue'?
TECHNICALLY: any day past 40 weeks. CLINICALLY: induction discussions usually start ~40-41 weeks per NICE NG207. ~10% of pregnancies go beyond 42 weeks if no induction. RISKS rise slightly post-42 weeks (stillbirth, meconium aspiration, large baby). PSYCHOLOGICALLY: 'overdue' can be tough — most births within 2 weeks of EDD.
Can my due date change?
YES — usually based on early ultrasound. Common revisions: (1) FIRST-TRIMESTER scan adjusts EDD; (2) Late scan rarely changes (less accurate); (3) IVF date precise from embryo transfer. RECORDED EDD remains in notes; clinical decisions based on it. IF DATES UNCERTAIN: New Ballard postnatal assessment confirms gestational age.
Why do some babies come early or late?
(1) FAMILY pattern; (2) PREVIOUS preterm / post-term; (3) MATERNAL factors (BMI, age, ethnicity); (4) FETAL factors (size, sex — boys slightly later); (5) PLACENTAL function; (6) PROGESTERONE / oxytocin signalling; (7) STRESS (mixed evidence). LARGELY unpredictable but probabilistic estimate. RANGE OF NORMAL wide (37-42 weeks).
What happens if I go past 40 weeks?
OFFERED MEMBRANE SWEEP at 40-41 weeks (vaginal exam to release prostaglandins; ~25% labour in 48h with favourable cervix). INDUCTION discussion at 41+0 weeks per NICE NG207 (sometimes 41+5). REASONS for induction past 41: stillbirth risk rises slightly + concerns rise. ALTERNATIVES: expectant management with twice-weekly fetal monitoring + scans. /calculators/membrane-sweep.
Will I really know I'm in labour?
PROGRESSIVE pattern: contractions getting STRONGER, CLOSER together, LONGER each. Some signs preceding: BACKACHE; PELVIC PRESSURE; 'SHOW' (mucus plug — pink/brown discharge); WATERS BREAKING (gush or trickle). FALSE LABOUR (Braxton Hicks): irregular, stops with rest. AT TERM: 5-1-1 rule (5 min apart, 1 min long, 1 hour) = hospital. /calculators/contraction-timer.
When should I tell people the due date?
PERSONAL CHOICE. SOME tell only a 'guess month' or 2-week window — manages expectations + reduces 'are you still pregnant?' messages near term. PARTNER + close family: usually exact EDD. LATER PREGNANCY: cope with calls + visitors better with vague timing. INDUCTION often pushes birth before EDD anyway.
Trimesters by week?
(1) T1: WEEKS 1-12 (some say 1-13 or 0-12); (2) T2: WEEKS 13-27 (or 14-27); (3) T3: WEEKS 28-BIRTH. MILESTONES: 12-week scan + dating; 20-week anomaly scan; 28+ weeks viability + most birth prep; 34-37 weeks late preterm; 37+ weeks term.
How accurate are 'baby size by week' comparisons?
POPULAR (papaya, butternut squash, watermelon) — fun but VERY APPROXIMATE. INDIVIDUAL fetal growth varies ±20-30% by week. CLINICAL: use estimated fetal weight (EFW) from ultrasound for individual baby; population averages for fruit comparisons. /calculators/baby-size-by-week /calculators/fetal-weight.
How does this relate to other calculators on BumpBites?
Companion: /calculators/due-date; /calculators/ivf-due-date; /calculators/pregnancy-week; /calculators/baby-size-by-week; /calculators/conception-date; /calculators/membrane-sweep; /calculators/contraction-timer.