Pregnancy Due Date
& Trimester Milestone Tracker
Calculate your exact Estimated Due Date (EDD), track daily gestational progress, explore weekly baby fruit size comparisons, and review your prenatal medical appointment roadmap.
Calculation Inputs
Dating from first trimester ultrasound scan and CRL
216 days remaining•9 Weeks 1 Days completed
Baby Size by Week Explorer
Slide or select week to see baby's size comparison
Green Olive
Embryo officially transitions to a fetus! Heart is fully partitioned into 4 chambers.
Standard Prenatal Ultrasound & Screening Milestones
Confirms intrauterine pregnancy, embryonic heartbeat (flicker), and gold standard CRL measurement.
Measures fluid at back of fetal neck (CRL 45–84 mm) to screen for chromosomal variations like Trisomy 21.
Comprehensive evaluation of brain, spine, 4-chamber heart, kidneys, stomach, limbs, and placenta location.
Routine oral glucose tolerance test (OGTT) and complete blood count (CBC) to screen for maternal anemia.
Routine vaginal/rectal culture and assessment of fetal cephalic presentation before labor.
How Due Dates Are Calculated: Clinical Comparison
Depending on your pregnancy history and available ultrasound data, obstetricians employ different clinical dating models.
Ultrasound CRL
The Gold Standard (±3–5 days). Direct millimeter measurement of the embryo in the 1st trimester. Supersedes calendar dates when discrepancies exceed 5–7 days.
Last Menstrual Period (LMP)
Naegele's Rule (+280 days). Assumes regular 28-day cycles with ovulation on Day 14. Accuracy can vary in women with irregular or prolonged cycles.
Conception / Ovulation
Biological Age (+266 days). Calculated directly from luteinizing hormone (LH) surge, basal temperature spike, or single act of intercourse.
IVF Embryo Transfer
100% Exact Chronology. Because fertilization occurs in the laboratory, dating is calculated by adding 263 days (Day 3 embryo) or 261 days (Day 5 blastocyst).
Frequently Asked Questions About Due Dates
What every expectant parent needs to know about delivery windows and ultrasound accuracy.
Do most babies actually arrive on their exact Estimated Due Date (EDD)? ▼
No. Only approximately 4% to 5% of babies are born on their exact EDD. Full-term pregnancy is clinically defined as a five-week window spanning from 37 weeks 0 days to 41 weeks 6 days. Approximately 80% of spontaneous labors occur between 38 and 42 weeks.
Can my due date change after my 20-week anatomy scan?
▼
Under international ACOG and BMUS guidelines, NO. Once an accurate first-trimester ultrasound due date is established, it becomes the definitive baseline and must never be altered by subsequent scans in the second or third trimester. Late scans evaluate fetal weight and growth percentiles, not gestational baseline age.
Why did my ultrasound give a different date than my last period? ▼
Menstrual dates assume ovulation occurs precisely 14 days after bleeding begins. In reality, ovulation fluctuates widely from cycle to cycle due to stress, illness, or hormonal variation. First-trimester ultrasound measures anatomical size with millimeter precision, bypassing menstrual ambiguity.