A calendar is a rough map, not a contract

People search for "week 5 symptoms" because an app drew a neat row of icons. Real early pregnancy is less obedient. The Eunice Kennedy Shriver National Institute of Child Health and Human Development says the primary sign is missing a period, or two or more periods in a row, and that many people notice other symptoms before that missed period. It also says a woman may have every common symptom, a few, or none. Having no nausea does not tell you the pregnancy is unhealthy. Having every symptom on a list does not confirm you are pregnant. The same page lists other reasons periods stop or shift: birth control pills, diabetes, polycystic ovary syndrome, eating disorders, and some medicines.

Clinicians usually count pregnancy weeks from the first day of the last menstrual period, not from conception. In a 28-day cycle, conception is often about two weeks after that date, so "4 weeks pregnant" can mean "about 2 weeks after fertilization." If your cycles are longer or irregular, that math moves. The ranges below are counted the way NICHD states them, in time after conception, and then translated loosely into the menstrual-period clock. They are ranges, not appointments.

Before a missed period

NICHD, drawing on patient-education sources it cites, places several symptoms in the first weeks after conception:

  • Tender, swollen breasts or nipples, sometimes as early as 1 to 2 weeks after conception. Hormonal change can make them sore or tingly, and they may feel heavier.
  • Fatigue, which some people notice as early as 1 week after conception. Progesterone rises to support the pregnancy and the milk-gland tissue. The body also moves more blood to carry nutrients. Tiredness at this stage is physiology, not laziness.
  • Headaches, which a sudden hormone rise can trigger.
  • Mood swings, which can start within a few weeks.
  • A more frequent need to urinate. NICHD attributes early frequency to human chorionic gonadotropin increasing blood flow in the pelvis.

Slight bleeding can also happen in this window. NICHD says one study found as many as 25% of pregnant women have slight bleeding or spotting lighter than a normal period (Deutchman, Tubay, and Turok, American Family Physician, 2009). It typically occurs when the fertilized egg implants, about 6 to 12 days after conception, and light bleeding remains common in the first 12 weeks. The American College of Obstetricians and Gynecologists puts first-trimester bleeding at 15 to 25 in 100 pregnancies, and says light bleeding or spotting can occur 1 to 2 weeks after fertilization as the egg implants. The cervix also bleeds more easily in pregnancy because more blood vessels are developing there. Spotting after sex, a Pap test, or a pelvic exam is not unusual.

ACOG's instruction is still to contact your obstetrician-gynecologist for any bleeding at any time in pregnancy. "Common" and "call" are both true. You are not overreacting by reporting spotting. You are also not being told that every spot is a loss.

Around the missed period

A missed period is the sign NICHD calls primary, and it is still not proof. Take that ambiguity to a clinician rather than to a stack of tests taken at midnight. Home urine tests look for hCG. Sensitivity differs by brand, and a test taken before hCG has risen can be negative in a pregnancy that is real. If you suspect pregnancy, NICHD says see a health care provider. A blood test or a repeat urine test, plus a plan for prenatal care, beats decoding faint lines.

Nausea and vomiting can start anywhere from 2 to 8 weeks after conception and can continue through pregnancy. The nickname "morning sickness" is misleading. NICHD says it can happen at any time of day. Food cravings and sudden dislikes of favorite foods are common and may last the whole pregnancy or come and go. None of these symptoms is specific. Stress, a stomach virus, a new medicine, or a change in birth control can imitate them.

If you cannot keep fluids down, call. Severe vomiting can dehydrate you. This article will not set a home threshold for hyperemesis gravidarum. That diagnosis is a clinician's, based on weight, urine, and how sick you are, not on a blog's definition of "a lot."

Through the rest of the first trimester

Bleeding remains the symptom that generates the most fear, so it is worth staying with ACOG's numbers a moment longer. Early pregnancy loss, also called miscarriage, is loss during the first 13 weeks. It happens in about 10 in 100 known pregnancies. Bleeding and cramping are signs. About half of women who have a miscarriage have no bleeding beforehand. Tissue left in the uterus after a loss may pass on its own or may be removed with medicine or a procedure. That choice is medical, and it is yours to make with a clinician, not from a comment thread.

Other causes of early bleeding that ACOG names are infection and ectopic pregnancy. An ectopic pregnancy implants outside the uterus, usually in a fallopian tube. If the tube ruptures, internal bleeding can cause weakness, fainting, pain, shock, or death. Sometimes vaginal bleeding is the only sign. Other symptoms include abdominal, pelvic, or shoulder pain, and they can start before you know you are pregnant. The pregnancy cannot continue and has to be treated with medicine or surgery. Call an ob-gyn or go to emergency care for one-sided pain, shoulder pain, fainting, or bleeding with dizziness.

Later bleeding has a different list. ACOG says bleeding later in pregnancy can be more serious: placental abruption, placenta previa, placenta accreta, and preterm labor (labor before 37 weeks). Those are not first-trimester topics for most readers of this page, but any bleeding still gets a call. Preterm-labor signs ACOG lists, for when pregnancy is further along, include a watery, mucus-like, or bloody discharge, pelvic pressure, a constant low backache, cramps, contractions, and fluid leaking from the vagina.

What a symptom list cannot tell you

Breast soreness that fades does not mean the pregnancy has ended. Fatigue that lifts in the late first trimester is a common story and is not a measurement of the embryo. Discharge that is thin and milky can be normal as the vaginal walls change; discharge that itches, burns, or smells strongly still deserves a check, pregnant or not. Comparing yourself with a friend who was sick from week 6 to week 14 will not predict your pregnancy.

Start prenatal care once a pregnancy is likely. Tell the clinician about medicines, including acne drugs and herbal products, because some are unsafe after conception. Ask about a prenatal vitamin and folic acid rather than guessing a dose from a bottle on a shelf. If you already track cycles, bring the first day of your last period. That date is more useful than a guessed conception day. The baby shopping can wait until after that visit, and a newborn needs less than most registry lists suggest anyway: a few soft sleepers, bodysuits, and swaddles, like the organic-cotton basics from Burt's Bees Baby (affiliate link), cover the first weeks.

Go in the same day, or to emergency care, for heavy bleeding, severe abdominal pain, shoulder pain, fainting, or vomiting that leaves you unable to drink. Call for any bleeding even when it is light. For the ordinary queasiness, sore breasts, and extra trips to the bathroom, a routine prenatal appointment is the right speed.

The question worth answering before that visit is simple: when was the first day of your last period, and have you had pain on one side?

Sources

This is not prenatal care. Bleeding, severe pain, and possible ectopic pregnancy need a clinician the same day, not another article.