Conception To Delivery—Timeline | Week-By-Week Due Date Map

Pregnancy time can feel slippery. People say “six weeks,” “ten weeks,” “first trimester,” or “due in May,” and it’s easy to wonder if you’re all using the same clock. This guide pins it down with a week-by-week view, plus the checkpoints that shape most pregnancies.

It helps you spot normal changes and know when to call your clinic.

Most clinicians count pregnancy from the first day of your last menstrual period (LMP), not from the day sperm meets egg. That’s why “week 4” often lines up with a missed period, not a visible bump.

Notes beat guesswork.

Conception To Delivery—Timeline At A Glance

Use this as your map. Weeks are counted from LMP. If you have early ultrasound dating, your care team may adjust the due date to match those measurements. ACOG How Long Pregnancy Lasts

Week range	What usually changes	Typical care checkpoints
Weeks 1–2	Body resets for ovulation; no embryo yet on the calendar	Track cycle dates; start prenatal vitamin with folic acid if you’re trying
Weeks 3–4	Fertilization and implantation; pregnancy test may turn positive	Confirm with home test; schedule first visit if positive
Weeks 5–6	Early embryo forms; hormone rise can drive nausea and fatigue	Plan first appointment; review meds and supplements
Weeks 7–9	Major early structures form; symptoms can peak	Dating ultrasound may be offered; baseline labs often happen
Weeks 10–13	Fetus moves; organs keep developing; placenta does more hormone work	Screening choices often land in this window
Weeks 14–20	Growth spurt; many feel more energy; movement may be felt later here	Anatomy scan is often scheduled around mid-pregnancy
Weeks 21–27	Kicks grow stronger; sleep and digestion can shift	Glucose screening and repeat labs are common in the late 20s
Weeks 28–36	Rapid weight gain; baby practices breathing and swallowing	Visits often get more frequent; position checks may begin
Weeks 37–40+	Baby reaches term in stages; body gears up for labor	Group B strep screening and birth planning often happen

How Pregnancy Weeks And Trimesters Are Counted

Two timelines run at once: gestational age (counted from LMP) and “time since conception” (often about two weeks less). Most appointments and test windows use gestational age, since LMP is easier to anchor than ovulation for many people.

Gestational age vs conception date

If you know ovulation or embryo transfer date, clinicians can convert that date into an “LMP-equivalent” start so the schedule lines up. If your cycle is longer or shorter than 28 days, the first estimate can drift; early ultrasound can tighten it.

Trimester boundaries

Trimesters are a tidy way to group changes, not a switch that flips overnight.

• First trimester: LMP to 13 weeks, 6 days
• Second trimester: 14 weeks, 0 days to 27 weeks, 6 days
• Third trimester: 28 weeks, 0 days to birth

Weeks 1–4 Start Of The Clock

Weeks 1 and 2 are “pre-pregnancy” on the pregnancy calendar. Your body is building the uterine lining and preparing to ovulate. If you’re trying to conceive, this is a good window to start folic acid, steady your sleep, and plan changes to alcohol or nicotine.

By week 3, fertilization can happen. The tiny cluster of cells travels to the uterus. Implantation often happens near the end of week 3 or early week 4. Some people notice light spotting. Many notice nothing.

Week 4 is the classic “missed period” week. Home tests can be positive now. If you’re getting mixed results, test first thing in the morning and repeat in two days.

Weeks 5–9 Early Growth And Early Symptoms

Weeks 5 to 6 are where symptoms often start to shout. Fatigue can feel like a wall. Nausea can show up with or without vomiting. If nausea is rough, try small, frequent meals, cold foods, and fluids in sips. If you can’t keep liquids down for a full day, call your clinic.

What’s forming inside

The embryo is laying down the basics: brain and spinal cord, early heart structures, and limb buds. This is a sensitive window for medicines, alcohol, and infections, so first visits often include a careful medication review.

First visit goals

Most first prenatal visits include dating, health history, and baseline tests. If you have one-sided pelvic pain, dizziness, or heavy bleeding, seek urgent care right away since ectopic pregnancy can be life-threatening.

Weeks 10–13 First Trimester Finish Line

By week 10, the embryo is now called a fetus. The placenta is taking over a lot of hormone work. Many people still feel nausea, but energy can start to return.

This window is also where many screening choices land. Depending on your clinic and your preferences, you may be offered blood tests, ultrasound screening, or both. Ask what each test can and can’t tell you, and what a “positive” screen means for next steps.

If you want a quick tour of what’s developing in each trimester, this ACOG guide is a solid reference. ACOG Fetal Growth By Trimester

Weeks 14–20 Second Trimester Momentum

Weeks 14 to 20 often feel steadier. Appetite may return. Sleep can improve. Some people notice round-ligament pain, a sharp pull in the lower belly with sudden movement. Slow turns, warmth, and gentle stretching can help.

Feeling movement

First movement can feel like fluttering, bubbles, or a soft tap. People who’ve been pregnant before may feel it earlier. An anterior placenta can make early kicks harder to spot. A lack of movement at 16 weeks isn’t a red flag on its own.

Anatomy scan

Many clinics schedule a detailed ultrasound in the 18–22 week range. It checks growth, anatomy, placenta location, and amniotic fluid.

Weeks 21–27 Mid-Pregnancy Rhythm

This stretch brings stronger kicks and a shifting center of gravity. You might notice heartburn, constipation, leg cramps, or new snoring. Hydration, fiber, and short walks can ease several of these at once.

Many people do glucose screening between 24 and 28 weeks. If the screen is abnormal, a longer test may follow. If you’re diagnosed with gestational diabetes, meal changes and home glucose checks are common first steps.

Weeks 28–36 Third Trimester Prep Phase

Baby gains fat, the brain keeps wiring up, and lungs practice breathing movements. Your body is carrying more load too, so aches and swelling can show up.

Visits get more frequent

Many practices move from monthly visits to twice-monthly visits in this span, then weekly later. Visits often include blood pressure checks, measuring fundal height, and symptom review.

Practical prep that pays off

• Pick a pediatrician and confirm their first-visit process
• Plan your route to the birth place at rush hour
• Pack a small bag: IDs, charger, comfy clothes, and toiletries

Weeks 37–42 Term Weeks And Labor Triggers

“Term” isn’t a single day. Many clinicians talk about early term (37–38), full term (39–40), late term (41), and post-term (42 and beyond). Your care team will weigh your health and baby’s status when planning induction timing.

Signs labor may be starting

• Cramping that returns in a pattern
• Back pain that builds in waves
• Fluid leaking that keeps going

Call right away for heavy bleeding, constant severe belly pain, severe headache with vision changes, or fluid that looks green or brown.

Conception To Delivery Timeline By Month For Quick Planning

Weeks are the most accurate way to track growth, but months help with calendar life. Here’s a practical conversion for planning appointments, travel, and work leave. Months don’t line up cleanly with weeks, so treat this as calendar shorthand.

Weeks	Calendar shorthand	Good planning tasks
1–4	Month 1	Confirm dates; start prenatal vitamin; book first visit
5–8	Month 2	Review meds; set nausea plan; line up early labs
9–13	Month 3	Choose screening options; plan travel with rest breaks
14–17	Month 4	Plan anatomy scan week; adjust sleep setup
18–22	Month 5	Start birth class research; confirm insurance steps
23–27	Month 6	Glucose screening; plan childcare or pet care for birth week
28–31	Month 7	Tour birth place; draft birth preferences; pack a simple bag
32–35	Month 8	Install car seat; set up safe sleep space; confirm leave paperwork
36–40+	Month 9+	Stock easy meals; review early labor signs; keep phone charged

When Dates Shift And What To Do Next

Many people get a due date at a first visit, then see it change after an ultrasound. In most cases it’s just better data. Early measurements are precise, while LMP dating depends on cycle length and memory.

If your due date changes, ask what method set the new date, and what week you are today on that method. Then update your calendar so tests land in the right windows.

Conception To Delivery—Timeline can also shift with twins, high blood pressure, diabetes, or prior preterm birth. Those situations may add extra visits or scans, or change birth planning. Ask what each extra check is watching for and what result would change the plan.

Trimester Rhythm That Keeps You Oriented

This simple loop keeps the timeline from feeling like a blur.

• Confirm your current week number at each visit
• Bring a short list of symptoms and questions
• Ask what’s next before you leave: labs, scan timing, next visit date

If you’re here after a positive test, start with the first table, then read the trimester sections that match your week. For planning, revisit the month table when you set work leave or travel. Conception To Delivery—Timeline feels calmer when your calendar matches your chart week.