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Calculate your due date, track weeks & trimester progress
đļ Complete Pregnancy Guide (2025)
How to Calculate Your Due Date
Your estimated due date (EDD) is calculated as 40 weeks (280 days) from the first day of your last menstrual period (LMP). This calculation assumes a 28-day menstrual cycle with ovulation occurring on day 14. Only about 5% of babies arrive exactly on their due date - most are born within 2 weeks before or after.
Methods to Calculate Due Date:
1. From Last Menstrual Period (LMP) - Most Common:
Formula: LMP + 280 days = Due Date
Naegele's Rule: LMP + 1 year - 3 months + 7 days
Example:
- Last period started: June 15, 2025
- Add 280 days (40 weeks)
- Due Date: March 22, 2026
2. From Conception/Ovulation Date:
Formula: Conception Date + 266 days = Due Date
Example:
- Conception date: June 29, 2025 (14 days after LMP)
- Add 266 days (38 weeks)
- Due Date: March 22, 2026
3. From Ultrasound Dating (Most Accurate):
- First trimester ultrasound (8-13 weeks) is most accurate (Âą5-7 days)
- Measures crown-rump length (CRL) or gestational sac
- Adjusts due date if measurement differs from LMP by >5 days
4. From IVF Transfer Date:
- Day 3 embryo: Transfer date + 263 days
- Day 5 blastocyst: Transfer date + 261 days
- IVF dates are most precise (conception date known exactly)
Pregnancy Trimesters Explained
| Trimester | Weeks | Months | Key Developments |
|---|---|---|---|
| First Trimester | Weeks 1-13 | Months 1-3 | All major organs form, heartbeat detected, highest miscarriage risk |
| Second Trimester | Weeks 14-27 | Months 4-6 | Feel baby move, learn gender, organs mature, "honeymoon period" |
| Third Trimester | Weeks 28-40+ | Months 7-9 | Rapid weight gain, lungs mature, baby prepares for birth |
Pregnancy Week-by-Week Development
First Trimester (Weeks 1-13):
| Week | Baby Size | Key Development |
|---|---|---|
| Week 4 | Poppy seed (2mm) | Embryo implants in uterus, positive pregnancy test possible |
| Week 5 | Sesame seed (3mm) | Heart begins to beat, neural tube forms |
| Week 6 | Lentil (5mm) | Heartbeat visible on ultrasound (100-160 bpm) |
| Week 7 | Blueberry (1cm) | Brain developing rapidly, arm/leg buds appear |
| Week 8 | Raspberry (1.6cm) | Fingers and toes forming, constantly moving |
| Week 9 | Grape (2.3cm) | Basic physiology in place, tail disappears |
| Week 10 | Kumquat (3.1cm) | Vital organs functioning, fingers/toes formed |
| Week 11 | Lime (4.1cm) | Hands can open/close, kick movements |
| Week 12 | Plum (5.4cm) | Reflexes developing, can suck thumb |
| Week 13 | Lemon (7.4cm) | Vocal cords form, fingerprints develop |
Second Trimester (Weeks 14-27):
| Week | Baby Size | Key Development |
|---|---|---|
| Week 14 | Peach (8.7cm) | Can make facial expressions, kidneys produce urine |
| Week 16 | Avocado (11.6cm) | Gender may be visible, eyes can move |
| Week 18 | Bell pepper (14cm) | Can hear sounds, developing sleep/wake cycles |
| Week 20 | Banana (16.4cm) | Anatomy scan week! Halfway point, feel movements |
| Week 22 | Spaghetti squash (27.8cm) | Can recognize your voice, eyelids/eyebrows formed |
| Week 24 | Corn (30cm) | Viability week - could survive with medical care |
| Week 26 | Lettuce (35.6cm) | Eyes open, responds to touch through belly |
| Week 27 | Cauliflower (36.6cm) | Recognizes voices, can hiccup |
Third Trimester (Weeks 28-40):
| Week | Baby Size | Key Development |
|---|---|---|
| Week 28 | Eggplant (37.6cm) | Can blink, eyelashes present, brain active |
| Week 30 | Cabbage (39.9cm) | Gaining 0.5 lb/week, practicing breathing |
| Week 32 | Jicama (42.4cm) | All five senses working, fingernails/toenails |
| Week 34 | Cantaloupe (45cm) | Central nervous system maturing, gaining fat |
| Week 36 | Romaine lettuce (47.4cm) | Shedding lanugo, may drop into pelvis |
| Week 37 | Swiss chard (48.6cm) | Full term! Baby is ready to be born |
| Week 38 | Leek (49.8cm) | Gaining immunity from you, vocal cords ready |
| Week 39 | Mini watermelon (50.7cm) | Brain still developing (continues until age 25!) |
| Week 40 | Pumpkin (51.2cm) | Due date! Average weight: 7.5 lbs (3.4 kg) |
Pregnancy Weight Gain Guidelines
Recommended Weight Gain by Pre-Pregnancy BMI:
| Pre-Pregnancy BMI | Category | Total Weight Gain | Rate (2nd/3rd Trimester) |
|---|---|---|---|
| Below 18.5 | Underweight | 28-40 lbs (12.5-18 kg) | 1 lb/week (0.5 kg/week) |
| 18.5-24.9 | Normal weight | 25-35 lbs (11.5-16 kg) | 1 lb/week (0.5 kg/week) |
| 25.0-29.9 | Overweight | 15-25 lbs (7-11.5 kg) | 0.6 lb/week (0.3 kg/week) |
| 30.0 and above | Obese | 11-20 lbs (5-9 kg) | 0.5 lb/week (0.2 kg/week) |
| Twins (normal weight) | Multiple pregnancy | 37-54 lbs (17-25 kg) | 1.5 lb/week (0.7 kg/week) |
Where Does the Weight Go?
- Baby: 7-8 lbs (3-3.6 kg)
- Placenta: 1-2 lbs (0.5-1 kg)
- Amniotic fluid: 2 lbs (1 kg)
- Uterus growth: 2 lbs (1 kg)
- Breast tissue: 1-2 lbs (0.5-1 kg)
- Blood volume: 3-4 lbs (1.5-2 kg)
- Fluids (extra): 2-3 lbs (1-1.5 kg)
- Maternal fat stores: 6-8 lbs (3-3.5 kg)
- Total: 25-35 lbs for normal BMI
Important Prenatal Tests & Appointments
| Week/Period | Test/Appointment | Purpose |
|---|---|---|
| Week 6-8 | First Prenatal Visit | Confirm pregnancy, dating ultrasound, blood work, medical history |
| Week 10-13 | NT Scan (Nuchal Translucency) | Screen for Down syndrome and other chromosomal abnormalities |
| Week 10-20 | NIPT (Non-Invasive Prenatal Testing) | Blood test for chromosomal conditions, can reveal gender |
| Week 15-20 | Quad Screen / AFP | Screen for neural tube defects and chromosomal issues |
| Week 18-22 | Anatomy Scan (20-week ultrasound) | Detailed scan of all organs, limbs, placenta; gender reveal! |
| Week 24-28 | Glucose Screening (GD test) | Screen for gestational diabetes |
| Week 28 | Rhogam Shot (if Rh-negative) | Prevent Rh incompatibility issues |
| Week 35-37 | Group B Strep (GBS) Test | Screen for bacteria that could affect baby during delivery |
| Week 36-40 | Weekly checkups | Monitor baby's position, dilation, blood pressure |
| Week 40-41 | Non-Stress Test (NST) | If overdue, monitor baby's heart rate and movements |
Frequently Asked Questions
Q: How accurate is the due date?
A: Only 5% of babies arrive on their exact due date. 90% are born between 37-42 weeks. Your due date is an estimate - baby will come when ready (usually Âą2 weeks from EDD).
Q: Can my due date change?
A: Yes. First trimester ultrasound (8-13 weeks) is most accurate and may adjust your due date if measurement differs from LMP calculation by more than 5-7 days.
Q: How is pregnancy counted - from conception or LMP?
A: From LMP (last menstrual period). Week 1-2 you're not actually pregnant yet. Conception typically occurs around week 2-3. This is why pregnancy is 40 weeks but baby develops for only 38 weeks.
Q: What week does each month start?
A: Month 1: Weeks 1-4, Month 2: Weeks 5-8, Month 3: Weeks 9-13, Month 4: Weeks 14-17, Month 5: Weeks 18-21, Month 6: Weeks 22-26, Month 7: Weeks 27-30, Month 8: Weeks 31-35, Month 9: Weeks 36-40.
Q: Is it 9 months or 10 months pregnant?
A: 40 weeks = 9 months + 1 week (or 10 lunar months). A pregnancy month averages 4.3 weeks, not exactly 4 weeks.
Q: When can I find out baby's gender?
A: NIPT blood test: 10+ weeks (99% accurate). Ultrasound: 16-20 weeks (anatomy scan at 18-20 weeks is standard). Gender reveal ultrasounds available at private clinics from 14 weeks.
Q: When will I feel baby move?
A: First pregnancy: 18-20 weeks. Subsequent pregnancies: 15-17 weeks (you recognize the feeling). At first, feels like flutters or bubbles. By 24 weeks, movements become stronger kicks.
Q: When is the second trimester?
A: Weeks 14-27 (months 4-6). Often called the "golden period" or "honeymoon trimester" - morning sickness usually ends, energy returns, not yet too uncomfortable.
Q: What is considered full term?
A: Early term: 37-38 weeks. Full term: 39-40 weeks. Late term: 41 weeks. Post-term: 42+ weeks. Babies born at 37+ weeks are generally healthy, but 39-40 weeks is optimal.
Q: How much weight should I gain each trimester?
A: Trimester 1: 2-4 lbs total (little to none). Trimester 2: 1 lb/week (12-14 lbs total). Trimester 3: 1 lb/week (12-14 lbs total). Total for normal BMI: 25-35 lbs.
Q: Can I fly during pregnancy?
A: Generally safe up to 36 weeks for domestic flights, 32 weeks for international. Best time: second trimester (14-27 weeks). Check airline policies. Stay hydrated, walk frequently, wear compression socks.