Pregnancy Due Date Laskuri
Käytä Pregnancy Due Date Laskuri laskuria nopeiden ja tarkkojen tulosten saamiseksi.
Kuinka käyttää tätä laskuria
- Anna First Day of Last Period
- Napsauta Laske-painiketta
- Lue tulos, joka näkyy laskurin alapuolella
How Your Due Date Is Calculated
The most widely used method for estimating due dates is Naegele's Rule, established by German obstetrician Franz Karl Naegele in 1812 and still in use today. The formula: Add 280 days (40 weeks) to the first day of your last menstrual period (LMP).
The 280-day figure is based on a 28-day cycle with ovulation occurring on day 14. It assumes pregnancy begins 14 days before a missed period — and technically counts those 2 weeks before conception as part of "pregnancy." This is why your healthcare provider says you are "4 weeks pregnant" when you're only 2 weeks past conception.
Quick calculation example: LMP = January 15 → Subtract 3 months → October 15 → Add 7 days → October 22. This Naegele shortcut gives the same result as adding 280 days.
Only about 4–5% of babies are born on their exact due date. A full-term pregnancy is defined as anywhere between 37 weeks 0 days and 40 weeks 6 days. Births between 41–42 weeks are considered late-term; 42+ weeks are post-term.
Pregnancy Trimesters: What to Expect
Pregnancy is divided into three trimesters, each with distinct developmental milestones and common maternal experiences:
| Trimester | Weeks | Baby Development | Common Symptoms |
|---|---|---|---|
| First | 1–12 | Brain, spinal cord, heart form; limb buds appear; face features develop | Morning sickness, fatigue, breast tenderness, frequent urination |
| Second | 13–26 | Rapid growth; fetal movement felt (~18–20 weeks); hearing develops | Most women feel better; back pain, round ligament pain begin |
| Third | 27–40 | Lungs mature; brain development accelerates; baby gains weight rapidly | Braxton Hicks, shortness of breath, frequent urination returns, sleep difficulty |
Key prenatal appointments to be aware of: First prenatal visit (8–10 weeks), nuchal translucency ultrasound (11–14 weeks), anatomy scan (18–20 weeks), glucose tolerance test (24–28 weeks), Group B strep screening (35–37 weeks), and weekly appointments from 36 weeks onward.
Conception Date vs LMP: Understanding the Difference
Many parents are confused when their due date seems earlier than expected based on when they think conception occurred. This happens because pregnancy is dated from the LMP, not from ovulation or conception.
If you know your conception date precisely (e.g., from IVF or a single unprotected encounter), add 266 days (38 weeks) to the conception date — this gives the same result as adding 280 days to your LMP in a 28-day cycle.
Irregular cycles: The standard calculation assumes a 28-day cycle. If your cycle is consistently longer or shorter, your ovulation day shifts, and so does your estimated due date. A 35-day cycle means ovulation likely occurred around day 21 (not day 14), pushing the due date ~7 days later. Your healthcare provider will often refine the due date with an early ultrasound, which is more accurate than LMP dating if there's a discrepancy of more than 7–10 days.
IVF pregnancies: Due dates for IVF are calculated differently. For a 3-day embryo transfer, add 266 days. For a 5-day (blastocyst) transfer, add 261 days. IVF due dates are generally more precise because the exact fertilization or transfer date is known.
Gestational Age Milestones
Understanding gestational age helps contextualize each stage of your pregnancy:
| Gestational Age | Milestone |
|---|---|
| 4 weeks | Positive home pregnancy test; embryo the size of a poppy seed |
| 6 weeks | Heartbeat detectable on transvaginal ultrasound (~110–160 bpm) |
| 10 weeks | Embryo becomes a fetus; all major organs formed; risk of miscarriage drops significantly |
| 12 weeks | End of first trimester; nuchal translucency screening; baby ~5.4 cm, 14 g |
| 16 weeks | Baby can make sucking/swallowing movements; possible gender identification on ultrasound |
| 20 weeks | Anatomy scan; "halfway" point; baby ~25 cm, 300 g |
| 24 weeks | Viability threshold — significant survival possible with intensive care |
| 28 weeks | Third trimester begins; 90%+ survival rate with medical care |
| 32 weeks | Lungs developing surfactant; baby ~42 cm, 1.8 kg |
| 37 weeks | Early term; considered safe for delivery |
| 40 weeks | Full term due date |
What Happens If You Go Past Your Due Date?
Going past your due date is extremely common. About 50% of first-time mothers give birth after their due date. Here's how post-dates pregnancy is managed:
- 40–41 weeks: Monitoring continues; non-stress tests and biophysical profiles may be ordered to ensure fetal wellbeing. Some providers offer membrane sweeping to encourage natural labor.
- 41–42 weeks: Most providers recommend induction between 41 and 42 weeks. Research (including the ARRIVE trial) shows that elective induction at 39–40 weeks does not increase C-section rates in low-risk pregnancies and may slightly reduce complications.
- Beyond 42 weeks: Placental function begins to decline; amniotic fluid may decrease; risks of fetal distress increase. Induction or cesarean delivery is typically recommended.
The most important thing to remember: your due date is an estimate, not an expiration date. If your pregnancy is progressing normally, going a few days past your due date is not cause for alarm. Maintain regular prenatal appointments and contact your healthcare provider if you notice reduced fetal movement, fluid leakage, or concerning symptoms at any stage.
Prenatal Nutrition and Lifestyle Essentials
During pregnancy, certain nutrients become especially critical:
- Folic acid: 400–800 mcg/day, ideally starting before conception, to prevent neural tube defects. Found in leafy greens, legumes, fortified cereals.
- Iron: Requirements nearly double in pregnancy (27 mg/day vs. 18 mg non-pregnant). Essential for fetal blood formation. Found in red meat, spinach, lentils.
- Calcium: 1,000 mg/day supports fetal bone development. Found in dairy, fortified plant milks, broccoli.
- DHA (Omega-3): 200–300 mg/day supports fetal brain and eye development. Found in fatty fish (salmon, sardines) or algae-based supplements.
- Vitamin D: 600 IU/day minimum; many women are deficient. Critical for calcium absorption and immune function.
Foods to avoid during pregnancy: Raw or undercooked meat/fish/eggs, unpasteurized dairy, deli meats (listeria risk), high-mercury fish (shark, swordfish, king mackerel, tilefish), liver in large amounts (vitamin A toxicity risk), and alcohol (no safe level established). Limit caffeine to under 200 mg/day (about 1–2 cups of coffee).
Frequently Asked Questions
How accurate is a due date calculator?
LMP-based calculations are accurate to within ±2 weeks for most women with regular 28-day cycles. An early ultrasound (before 12 weeks) can refine the estimate to within ±5–7 days, as fetal size in early pregnancy is highly predictable. Only 4–5% of babies are born on their exact due date.
What if my cycle is not 28 days?
For cycles longer than 28 days, your due date shifts later by the number of extra days in your cycle (e.g., a 35-day cycle pushes due date ~7 days later). For shorter cycles (e.g., 21 days), the due date moves ~7 days earlier. A first-trimester ultrasound is the most reliable way to establish accurate dating if your cycles are irregular.
Can the due date change during pregnancy?
Yes. Your provider may revise your due date based on ultrasound measurements if they differ significantly from LMP dating. In general, if the ultrasound is within 7 days (first trimester) or 10–14 days (second trimester) of the LMP date, most providers keep the original due date. If the discrepancy is larger, they'll typically use the ultrasound date.
What is the difference between gestational age and fetal age?
Gestational age is counted from the first day of your last menstrual period — so at the moment of conception you're already about 2 weeks "pregnant" by this measure. Fetal age (sometimes called embryonic age or conceptional age) is counted from actual fertilization, and is typically 2 weeks less than gestational age.
When does morning sickness usually end?
For most women, morning sickness peaks between weeks 8–10 and resolves by week 12–14 (end of first trimester). About 25% of women experience it beyond the first trimester. Hyperemesis gravidarum (severe nausea and vomiting causing dehydration and weight loss) affects 0.5–2% of pregnancies and requires medical treatment.
Is it safe to exercise during pregnancy?
For most healthy pregnancies, 150 minutes of moderate-intensity exercise per week is recommended by ACOG (American College of Obstetricians and Gynecologists). Walking, swimming, prenatal yoga, and moderate strength training are all generally safe. Avoid contact sports, activities with fall risk, and exercises lying flat on your back after the first trimester. Always get clearance from your healthcare provider.
What are signs of labor starting?
Early signs include: bloody show (mucus plug discharge), regular contractions that increase in frequency and intensity, and water breaking (rupture of membranes). Braxton Hicks contractions are irregular practice contractions and are normal from mid-pregnancy onward. Contact your healthcare provider when contractions are 5 minutes apart, lasting 1 minute, for at least 1 hour (the 5-1-1 rule), or immediately if your water breaks.
How is a due date calculated for twins?
Twin (and higher-order multiple) pregnancies use the same LMP calculation. However, twins are typically delivered earlier than singletons. Dichorionic-diamniotic (DCDA) twins are usually delivered at 38 weeks; monochorionic-diamniotic (MCDA) at 36–37 weeks; monochorionic-monoamniotic (MCMA) twins as early as 32–34 weeks due to cord entanglement risk.
💡 Tiesitkö?
- The average human pregnancy lasts 280 days (40 weeks) from the first day of the last menstrual period — established by German physician Franz Karl Nägele in 1812.
- Only about 5% of babies are born on their predicted due date; 80% arrive within 2 weeks either side.
- Elephants have the longest pregnancy of any land mammal at approximately 22 months.
Viimeksi päivitetty: March 2026