Calculate your due date in seconds. Enter your last period, conception date, ultrasound results, or IVF transfer date to get your complete pregnancy timeline—week-by-week development, milestones, and appointment schedules included.
This calculator offers four methods with different accuracy levels depending on what information you have.
The Last Menstrual Period (LMP) method is what your doctor will ask for at your first appointment. Enter the first day of your last period—the day bleeding started, not when it ended. If you have regular periods, this method gives you a solid estimate. For cycles longer or shorter than 28 days, adjust the cycle length. The calculator assumes ovulation happens 14 days before your next period (not 14 days after your last one), so a 32-day cycle means you ovulated around day 18.
The Conception or Ovulation Date method cuts out the guesswork. If you were tracking ovulation with test strips, temperature charts, or fertility apps, enter that date. Pregnancy is 266 days from conception—shorter than the 280 days counted from LMP because we're not adding those two pre-conception weeks.
Ultrasound dating is the most accurate, especially between 6 and 12 weeks. Early embryos all grow at the same rate, so measurements are precise within a few days. Enter the date of your ultrasound and the gestational age from your report (like "12 weeks, 3 days"). If your ultrasound date differs from your LMP date by more than a week, doctors will usually go with the ultrasound.
IVF Transfer dating is the gold standard because embryo age is exact. Day 3 and day 5 transfers are most common. The calculator adjusts for embryo age at transfer—whether fresh or frozen doesn't matter, only how old the embryo was.
Pregnancy dating is backwards.
You're "two weeks pregnant" before you even conceive.
Medical dating counts from the first day of your last period, not from conception. Before ultrasounds existed, the first day of bleeding was the only date most women could pin down. Ovulation timing varies, but your period start is obvious. The medical system standardized on this decades ago, and it stuck. Even with modern technology, LMP remains the reference point.
Naegele's Rule: Take your LMP, add 7 days, subtract 3 months. Or just add 280 days. Same result. Example—LMP on March 1, add 7 days = March 8, subtract 3 months = December 8. Due date: December 8.
Simple formula.
The 280-day calculation assumes a 28-day cycle with ovulation on day 14. Conception happens around day 14, so the actual time from conception to birth is 266 days. Those extra 14 days? They're the two weeks before you conceived. This is gestational age, measured from LMP. Embryonic age or fetal age, measured from conception, is always about two weeks less.
When your doctor says you're 10 weeks pregnant, they mean 10 weeks since LMP—the embryo has been developing for about 8 weeks. This two-week gap stays constant. At your 20-week anatomy scan, the baby has been growing for 18 weeks since conception.
Full-term pregnancy is 40 weeks gestational age, or 38 weeks from conception. Nine months is a rough estimate—pregnancy is closer to 9.5 calendar months or 10 lunar months (28-day cycles).
Everything in obstetrics references gestational age from LMP. That's the number your doctor tracks, the number on ultrasound reports, and the number pregnancy apps use.
That's the system.
Your due date is an estimate, not a deadline.
Only 5% of babies arrive on their exact due date. About 80% are born between 38 and 42 weeks, a four-week range that's considered normal. Pregnancies don't all progress at the same rate. Genetics, baby's position, maternal health, stress levels—they all affect timing.
Interestingly, first-time mothers deliver around 40 weeks and 5 days on average. Subsequent pregnancies? Around 40 weeks and 3 days. Small difference, but consistent across populations.
For twins and triplets, due dates matter less. Twins arrive around 36 weeks, triplets around 32 weeks. More babies = earlier delivery.
Different methods give different accuracy levels. LMP dating assumes regular 28-day cycles and ovulation on day 14. If your cycles are irregular or longer/shorter, LMP dating can be off by a week or more. A woman with 35-day cycles ovulates around day 21, not day 14, which shifts both conception date and due date. The good news: early ultrasounds (6-12 weeks) are more accurate. Embryo measurements correlate tightly with gestational age, within 3-5 days. Later ultrasounds lose precision because babies grow at different rates—a 20-week scan might be accurate within a week, a third-trimester scan could be off by 2-3 weeks. Good for checking growth and position but not for changing your due date. IVF dating is most precise since embryo age is exact at transfer. IVF due dates are accurate within a day or two.
Can't beat early dating scans.
Accuracy matters because decisions about induction, monitoring, and interventions depend on gestational age. If your due date is wrong, you might be induced too early or monitored for "post-term" when you're in the normal range. Doctors adjust due dates based on early ultrasounds for this reason—they're the gold standard.
Dating matters.
That accuracy depends heavily on your dating method.
LMP and ultrasound dating disagree constantly.
Here's which one to trust.
LMP dating works for women with regular 28-day cycles who ovulate on day 14, but cycles between 21 and 35 days are all normal. If yours is 32 days, you'll ovulate around day 18, not day 14—using day 14 in the formula makes your due date about 4 days early. Irregular cycles make pinpointing ovulation guesswork. Your conception date could be off by a week or more. Women with PCOS face this problem constantly since irregular cycles make LMP-based dating unreliable. Ultrasound measures the embryo directly, and in the first trimester, crown-rump length correlates tightly with gestational age since all embryos grow at nearly identical rates early on.
Doctors perform dating ultrasounds between 8 and 12 weeks. Measurements are accurate within 3-5 days. If this ultrasound differs from your LMP date by more than 7 days, most doctors revise your due date to match the ultrasound. The ultrasound is more reliable than memory or cycle regularity.
Later ultrasounds lose accuracy. By the second trimester, genetic variation kicks in: some babies are bigger, some smaller. A 20-week scan might show a baby measuring 19 weeks 3 days or 20 weeks 5 days, but that could be size variation, not a dating error. Third-trimester scans have error margins up to 2-3 weeks. Good for growth checks, not for revising due dates.
Know your LMP and had regular cycles? That's a good starting point. Confirm with a first-trimester ultrasound.
Significant discrepancy? Go with the ultrasound.
IVF patients don't need ultrasounds for dating; the transfer date gives exact info. But even IVF pregnancies get ultrasounds to confirm viability and check development. They just don't use them to change the due date.
Three trimesters of 13-14 weeks each.
During the first trimester (weeks 1-13), all major organs form. The embryo develops a beating heart, brain structures, limbs, and facial features by week 8—when it officially becomes a fetus. This trimester carries the highest miscarriage risk—10-20% of known pregnancies end before week 10.
Symptoms? Fatigue, nausea that can strike any time (not just mornings), breast tenderness, frequent urination. Progesterone and hCG surge, causing most of these issues. Some women feel fine; others are miserable. The good news: nausea improves around week 12-13 as hormones stabilize.
Energy returns during the second trimester (weeks 14-27). Nausea fades. The baby bump isn't overwhelming yet. Many call this the "honeymoon phase." Baby growth accelerates, and the anatomy scan around week 20 reveals organs, structures, and often the sex. Baby bumps become visible between weeks 16-20 for first pregnancies, earlier for subsequent ones. Quickening (first felt movements) happens between weeks 16-25. First-time mothers might not recognize early flutters, but experienced mothers notice sooner. By week 24, baby reaches viability and could survive outside the womb with intensive medical care, though outcomes improve dramatically with each additional week.
During the third trimester (weeks 28-40), baby gains most of its weight. Fat stores develop, organs mature for life outside the womb, brain development accelerates, lungs practice breathing. Baby settles head-down by weeks 32-34.
Physical challenges intensify during these final weeks. Large, heavy belly makes movement, sleep, and breathing harder. Braxton Hicks contractions become common. Back pain. Pelvic pressure. Swollen feet and ankles. Constant bathroom trips. The final weeks bring waiting, discomfort, anticipation, and nesting instincts (that sudden urge to clean and organize everything).
Almost there.
Gestational age is expressed as weeks and days: "12 weeks, 3 days."
Count the days from your LMP to today, then convert to weeks and days. LMP was 87 days ago? That's 12 weeks (84 days) plus 3 extra days, written as 12 weeks, 3 days or 12+3.
Your gestational age "week" changes on the same day of the week your period started—LMP on a Monday means you move to the next week every Monday. Pregnancy apps and doctors use week + day notation because it's more precise than "you're in your 12th week," which could mean anywhere from 11+0 to 11+6.
Gestational age and fetal age aren't the same. Gestational age counts from LMP and includes those two pre-conception weeks. Fetal age counts from conception and runs about two weeks less.
When you read "at 8 weeks, the embryo has fingers and toes," that's 8 weeks gestational age—6 weeks post-conception.
Tracking apps use gestational age exclusively. When an app says you're 20 weeks pregnant, it's counting from LMP. Doctors, midwives, ultrasound reports—all use gestational age. If someone mentions fetal age, they'll specify "post-conception."
Obstetric milestones tie to weeks: First trimester screening at 11-13 weeks. Anatomy scan at 18-22 weeks. Viability at 24 weeks. Full term at 37 weeks.
Pregnancy is 40 weeks + 0 days, or 280 days.
Past your due date? You'll hear 40+3 (40 weeks, 3 days) or 41+1. Post-term pregnancy is 42 weeks or beyond—when most doctors recommend induction.
Those weeks mark important milestones.
Most home pregnancy tests work by the first day of a missed period—around 4 weeks gestational age. They detect hCG, the pregnancy hormone. Blood tests at the doctor's office can confirm pregnancy even earlier.
Heartbeat becomes detectable on transvaginal ultrasound around week 6. The embryonic heart started beating around 5-6 weeks. Hearing it? That significantly lowers miscarriage risk.
The embryonic stage ends at week 8, and the fetal stage begins. All major organs and structures are present now, though not fully developed. From here on, growth and maturation dominate rather than organ formation.
Miscarriage risk drops below 5% by weeks 12-13. Many parents wait until now to announce. Nausea improves as hormones stabilize.
Nuchal translucency scanning between weeks 11-14 is optional. This screening ultrasound measures fluid at the back of baby's neck and, combined with blood tests, assesses risk for chromosomal abnormalities like Down syndrome. Not diagnostic—helps determine if further testing is needed.
Non-invasive prenatal testing (NIPT) from week 10 onward analyzes fetal DNA from mother's blood. It screens for chromosomal conditions and reveals baby's sex. Very accurate with no miscarriage risk.
The detailed mid-pregnancy ultrasound between weeks 18-22 checks everything—organs, limbs, spine, brain, heart. It looks for structural abnormalities and confirms gestational age. Most parents find out sex here.
Quickening—the first felt movements—happens between weeks 16 and 25. First-time mothers notice it around week 20. Experienced mothers feel those flutters earlier, sometimes by week 16.
Baby has a chance of survival outside the womb with intensive NICU care starting at week 24. Fortunately, survival rates increase dramatically with each week. By 28 weeks, outcomes improve significantly; by 32 weeks, most babies do very well.
Glucose screening between weeks 24-28 tests for gestational diabetes. You drink a sugary beverage, blood sugar gets tested an hour later. High results trigger a longer glucose tolerance test.
Week 28 marks the final stretch. Baby gains most weight in these last weeks. Prenatal visits increase to every two weeks, then weekly.
Most babies settle into vertex (head-down) position by weeks 32-34. If baby is breech after 36 weeks, doctors may attempt external cephalic version (manually turning the baby) or discuss C-section.
Between weeks 35-37, a quick swab checks for Group B strep bacteria. Common and harmless in adults but dangerous for newborns during delivery. Positive result? IV antibiotics during labor.
Babies born at 37+ weeks are considered full term. But research shows 39-40 weeks is optimal—especially for brain maturation. Early term babies (37-38 weeks) have higher risks of breathing problems and NICU stays.
Week 40 is the estimated arrival date. Only 5% of babies arrive on this day.
Past your due date? Closer monitoring kicks in—non-stress tests, ultrasounds checking baby and fluid levels. Most doctors recommend induction by 41-42 weeks to reduce risks like placenta aging and decreased fluid.
Tests and appointments—here's what happens when.
Your first prenatal visit happens between weeks 8-10. The doctor confirms pregnancy, establishes your due date, and reviews your medical history. Expect a physical exam and blood tests—blood type, Rh factor, anemia screening, infection checks, rubella immunity. Maybe an early ultrasound.
The first ultrasound between weeks 8-12 confirms the pregnancy is in your uterus (not ectopic). It checks for a heartbeat, measures the embryo to date your pregnancy, and determines if you're having one baby or multiples.
Nuchal translucency scanning between weeks 11-14 is optional first-trimester screening. Ultrasound measures neck fluid, combined with blood tests. High measurements may indicate increased risk for Down syndrome, trisomy 18, or heart defects. Results help you decide whether to pursue diagnostic testing like CVS or amniocentesis.
NIPT screens for chromosomal abnormalities from week 10 onward by analyzing fetal DNA in your blood. It's accurate for conditions like Down syndrome and reveals baby's sex. Optional but often offered to women over 35 or those with abnormal screening results.
Chorionic villus sampling (CVS) between weeks 10-13 is diagnostic—not screening. It's invasive and only done when there's high risk of genetic conditions. A placental tissue sample gets tested for chromosomal abnormalities and genetic disorders. Miscarriage risk sits at 1 in 300-500. But results? Definitive.
The quad screen (weeks 15-20) is a second-trimester blood test. It screens for Down syndrome, trisomy 18, and neural tube defects by measuring four substances in your blood. Less accurate than NIPT but useful if you skipped earlier screening.
Amniocentesis between weeks 15-20 is another diagnostic test. A needle through the abdomen into the amniotic sac collects fluid containing fetal cells. Tests for genetic and chromosomal conditions with high accuracy. Miscarriage risk about 1 in 300-500. Offered to women with abnormal screening or high risk.
This detailed ultrasound between weeks 18-22 examines everything: organs, brain, spine, heart, kidneys, limbs, face. It checks for structural issues, measures growth, and assesses placenta and fluid levels.
Glucose screening happens between weeks 24-28. You drink a sugary beverage, blood gets drawn an hour later. High blood sugar suggests gestational diabetes. Elevated results trigger a 3-hour glucose tolerance test. Gestational diabetes affects 6-9% of pregnancies and requires dietary changes and monitoring.
The Tdap vaccine (weeks 27-36) protects against tetanus, diphtheria, and whooping cough. Given during pregnancy, it passes antibodies to your baby—protecting them in the first months before they can be vaccinated. Recommended for every pregnancy.
About 25% of women carry Group B strep without symptoms. A quick swab of the vagina and rectum (weeks 35-37) checks for it. If positive, you'll get IV antibiotics during labor to protect your baby.
During the final month (week 36+), visits shift to weekly. Your provider checks blood pressure, urine, baby's position and heart rate, fundal height (belly size). You'll discuss labor signs, birth plans, what to expect.
Past your due date? Doctor may order non-stress tests and ultrasounds to monitor baby's heart rate, movement, and fluid levels.
IVF pregnancies follow the same test schedule but date differently.
IVF dating is most precise—embryo age is exact at transfer.
In IVF, eggs are retrieved, fertilized in the lab, allowed to develop for a few days, then transferred. Most common transfer days are day 3 (cleavage stage) and day 5 (blastocyst stage). Day 6 blastocysts occasionally get transferred.
Day 3 embryo transfer: Embryo is three days old; add 263 days to transfer date for due date. Why 263? Full-term pregnancy is 266 days from conception, and the embryo is already 3 days old.
Day 5 embryo transfer (blastocyst): Embryo is five days old. Add 261 days to transfer date. Day 5 transfers are more common because blastocysts have higher implantation rates and allow doctors to select the best embryo.
Day 6 embryo transfer? Add 260 days.
Fresh vs frozen (FET) doesn't change the calculation. What matters is embryo age at transfer. Frozen embryo transfers are common and have similar (sometimes better) success rates because the uterine lining can be optimized.
IVF due dates rarely get adjusted based on ultrasounds. Early ultrasounds confirm implantation, check for multiples, ensure pregnancy is developing—not to revise the due date. Transfer date is the gold standard.
After the first trimester, IVF pregnancies are managed like naturally conceived pregnancies. The dating is just more accurate.
Twins, triplets, and higher-order multiples have different timelines. Due dates are calculated the same way, but delivery happens earlier.
Twins deliver around 36 weeks on average, though some make it to 37-38. Triplets average 32 weeks. Quads and higher rarely reach 30 weeks. More babies = earlier delivery—space constraints, placental insufficiency, increased complication risk.
The 40-week due date is theoretical for multiples. Doctors monitor with frequent ultrasounds—checking growth, fluid levels, positions. Many providers recommend delivery by 38 weeks for twins even without labor, to reduce stillbirth and complication risks.
Identical twins sharing a placenta (monochorionic) need more intensive monitoring—higher risks, including twin-to-twin transfusion syndrome (TTTS) where one twin gets more blood flow than the other. Ultrasounds every two weeks starting in the second trimester are common.
The due date still serves a purpose for tracking gestational age, which is critical for managing risks, scheduling tests, deciding delivery timing. Doctors talk about "gestational age at delivery" rather than "days overdue"—going to 40 weeks is rare and not desirable.
Twin pregnancies come with more testing—extra ultrasounds check for growth discordance (one twin significantly smaller). Doctors watch for preterm labor signs more carefully. Bed rest used to be common; current evidence doesn't support it for preventing preterm birth in multiples.
Your "due date" with multiples is a reference point. Your doctor will discuss realistic delivery timing based on your situation. Twins might be delivered at 37-38 weeks. Triplets are delivered by scheduled C-section around 32-34 weeks. Higher-order multiples need NICU time because they're born preterm.
Full term weeks aren't equal.
In 2013, ACOG refined the definition to reflect research about fetal brain maturation.
Early term spans 37 weeks 0 days to 38 weeks 6 days. Babies are full term and healthy, but they have higher rates of respiratory issues, feeding difficulties, and jaundice compared to 39-week babies. Brains are still developing.
Full term: 39 weeks 0 days to 40 weeks 6 days. The sweet spot—fewer NICU admissions, better breathing, better feeding, better long-term development. Brain grows and matures significantly between 37 and 39 weeks.
Late term runs from 41 weeks 0 days to 41 weeks 6 days. A week past your due date is normal. Risks increase—larger baby size (complicates delivery), decreased fluid, placenta aging. Doctors monitor closely.
Post-term means 42 weeks and beyond. Most providers recommend induction because risks continue rising—stillbirth, meconium aspiration (baby inhaling stool), placental insufficiency.
Research showed elective inductions and C-sections before 39 weeks led to worse outcomes, even though 37-38 week babies were "full term." Hospitals scheduled deliveries for convenience at 37-38 weeks without realizing the disadvantages. New categories encourage waiting until 39 weeks unless there's a medical reason for earlier delivery.
37-38 week babies do fine. But if there's no medical reason to deliver, waiting until 39 weeks gives baby the best chance—lung maturity, brain development, feeding coordination all improve with those extra weeks.
Induction before 39 weeks happens when medically necessary—preeclampsia, gestational diabetes, signs baby isn't thriving. In those cases, risks of continuing pregnancy outweigh benefits of waiting. For healthy, low-risk pregnancies, 39 weeks is the goal.
Know when to head to the hospital.
Regular contractions are the main sign of true labor. Uterine muscles tighten and relax. In labor, they become regular, progressively stronger, longer, closer together. Time from the start of one contraction to the start of the next. True labor contractions don't stop when you change positions or walk—they intensify.
5-1-1 rule: Common guideline for when to go. Contractions 5 minutes apart, each lasting 1 minute, for at least 1 hour. First-time mothers might wait longer at home; mothers who've given birth before progress faster and should head in sooner.
Water breaking: Amniotic sac ruptures, releasing fluid. Might be a big gush or slow trickle. Fluid is clear or pink. Green or brown could indicate meconium (baby's first stool)—requires immediate evaluation. If your water breaks, call your doctor right away, even without contractions. Most providers want delivery within 24 hours to reduce infection risk.
Bloody show is a small amount of blood-tinged mucus discharged when the mucus plug sealing the cervix is released as cervix begins to dilate. Can occur days or even a week before labor starts—not an emergency. Heavy bleeding (soaking a pad)? Call immediately.
Lower back pain that's constant or comes in waves can signal labor, especially if it radiates to the abdomen and feels different from typical pregnancy back discomfort. Some women experience "back labor"—contractions felt in lower back due to baby's position.
Pelvic pressure increases as baby drops lower (called "lightening" or "engagement"). Can happen weeks before labor in first pregnancies or right before labor in subsequent ones.
Braxton Hicks are practice contractions—irregular, don't increase in intensity, stop with hydration, rest, or position changes. True labor contractions are regular, painful, progressive. Unsure? Time them and see if they follow a pattern.
Call your doctor immediately for: Heavy vaginal bleeding (not just bloody show), severe abdominal pain that doesn't ease, sudden severe headache with vision changes (could be preeclampsia), water breaking (especially if fluid is discolored), decreased fetal movement (always call if baby moves less than usual), anything that feels wrong.
Trust your instincts.
Labor unfolds differently for everyone. Some have hours of early labor at home; others go from zero to intense quickly. Your doctor will give personalized guidance based on your pregnancy, distance from hospital, risk factors.
Common myths, debunked.
Myth: The due date is when your baby will arrive.
Only 5% of babies are born on their exact due date. It's the middle of a range, not a finish line. Most arrive within two weeks before or after. Treating it as a firm deadline sets you up for disappointment.
First babies are always late? Not true. First-time mothers deliver later on average (40 weeks, 5 days vs 40 weeks exactly), but "always" is wrong. Plenty of first babies arrive early.
Myth: Full moons cause more births.
Studied repeatedly—no correlation between lunar phases and birth rates. Hospitals don't see spikes during full moons.
Carrying high means girl, low means boy? Faster heart rate means girl? None of this is true. How you carry depends on body shape, muscle tone, baby's position. Heart rate varies and doesn't correlate with sex or due date.
Myth: You can calculate exact conception date and get a perfect due date.
Even if you know the exact day you had sex, conception doesn't happen that day. Sperm survive up to 5 days; egg survives 12-24 hours after ovulation. "Conception date" is an estimate within a window, not a precise moment (unless you did IVF).
Due dates are 9 months from conception? Pregnancy is about 9 months, but more accurately 40 weeks or 280 days from LMP. Works out to 9 months and 1 week, or closer to 10 lunar months. "9 months" is convenient shorthand.
Myth: If you go past your due date, something's wrong.
Going to 41 weeks is normal—about half of pregnancies go past 40 weeks. As long as you and baby are monitored and everything looks good, no reason to panic. Post-term (42 weeks+) is when intervention is recommended.
Later ultrasounds showing baby measuring ahead or behind? That's size variation, not dating errors. Due dates are only adjusted based on early first-trimester ultrasounds (before 13 weeks) when all embryos grow at the same rate. Baby in 90th percentile at 30 weeks doesn't mean you're 32 weeks pregnant—it means you have a bigger baby.
These methods get recommended constantly but lack proof: spicy food won't induce labor (might give you heartburn though). Sex could help since semen contains prostaglandins that soften the cervix, but it won't start labor unless your body is ready. Same with walking—good exercise, but won't force labor. When your body and baby are ready, labor happens.
Both premature birth and post-term pregnancy carry risks. Modern medicine has dramatically improved outcomes for early babies.
Premature birth is delivery before 37 weeks. About 10% of U.S. babies are born preterm. The earlier the birth, the higher the risks. Extremely preterm (before 28 weeks) face serious challenges; late preterm (34-36 weeks) do well but still have higher risks than full-term babies.
At 24 weeks, viability begins. With intensive NICU care, some survive, but risks are enormous: severe lung problems, brain bleeds, vision and hearing issues, developmental delays. Survival rates around 50-70% at 24 weeks. Each week improves outcomes.
By 28 weeks, survival exceeds 90%. Babies still need weeks or months of NICU care, but fortunately severe complications are less common. Lung development is further along, and steroids given before birth can accelerate lung maturity.
Late preterm (34-36 weeks) look nearly full term but have higher rates of respiratory distress, temperature regulation problems, feeding difficulties, jaundice, low blood sugar. More likely to be readmitted in the first weeks. Most do fine with extra support, but they're not equivalent to 39-week babies.
Causes of preterm birth: preterm labor (contractions that won't stop), preterm premature rupture of membranes (water breaking early), medical conditions like preeclampsia or placenta problems, infections, multiple pregnancies, sometimes unknown reasons. Some preterm births are medically indicated when continuing pregnancy is riskier than delivering early.
Post-term pregnancy (42 weeks+) carries different risks. Placenta can age and become less efficient at delivering nutrients and oxygen. Amniotic fluid may decrease, increasing cord compression risk. Baby may grow very large (macrosomia), complicating vaginal delivery. Stillbirth risk is higher post-term than at 40 weeks.
Meconium passage (baby's first bowel movement) is more common post-term. If baby passes meconium before birth then inhales it (meconium aspiration), it can cause respiratory problems.
Most doctors recommend induction between 41-42 weeks—some offer at 41 weeks, others wait closer to 42. Decision depends on your situation, cervical readiness, baby's condition on monitoring tests.
Non-stress tests and biophysical profiles (ultrasound checks of baby's movement, breathing practice, muscle tone, fluid) monitor post-term pregnancies. Reassuring results? Waiting longer is safe. Concerning signs? Induction or C-section may be recommended.
For both preterm and post-term, close monitoring and good prenatal care make a difference. Signs of preterm labor? Getting to the hospital quickly allows medications to delay labor and steroids to mature baby's lungs. Overdue? Regular monitoring catches problems early and guides timing decisions.
Conception date is an estimate unless you did IVF.
Sperm survive in the female reproductive tract up to 5 days under optimal conditions (around ovulation when cervical mucus is fertile). An egg, once released at ovulation, survives 12-24 hours. Fertilization happens when sperm meets egg—anywhere from minutes after sex to 5 days later.
This creates a conception window of about 5-6 days. Had sex Monday, ovulated Thursday? Conception happened Thursday, not Monday. But you have no way to know the exact moment unless you were tracking ovulation with tests, temperature charting, or ultrasound monitoring.
Standard assumption: ovulation happens 14 days after the first day of your last period in a 28-day cycle. Conception occurs within a day or so of ovulation, so estimated conception date is LMP + 14 days. Woman whose LMP was March 1? Estimated conception around March 15.
Longer or shorter cycle? Ovulation day shifts. 32-day cycle ovulates around day 18. 25-day cycle ovulates around day 11. The 14-day number comes from the luteal phase (time between ovulation and next period), which is consistent at 12-14 days. The first half (follicular phase) varies more.
Irregular cycles make estimating conception harder—some months you might ovulate on day 12, others on day 20. Without tracking, you're guessing. This makes LMP-based due dates less reliable and ultrasounds become the primary dating tool.
Were you tracking ovulation? You can estimate more accurately. Positive ovulation test means you'll ovulate within 24-36 hours. Temperature spike confirms ovulation happened. Fertile cervical mucus (clear, stretchy) signals days leading up to ovulation.
Some women know their exact conception date because they had sex only once that cycle or were doing fertility treatments with timed intercourse. Even then, there's still a 5-day window because of sperm survival.
In IVF, conception date is exact—the day egg and sperm were combined in the lab. For day 5 blastocyst transfer, conception was 5 days before transfer.
Why does this matter? Mostly it doesn't. Doctors care about gestational age (from LMP), not the exact moment of conception. But some parents want to know for sentimental or personal reasons, especially if there are paternity questions or they were tracking fertility closely.
Bottom line: unless you did IVF, your conception date is an estimate within a few days—and doesn't need to be exact for a healthy pregnancy.