At 5 weeks pregnant, you’re about one week past your missed period, and the embryo inside you is roughly 2mm long, about the size of a sesame seed. Despite that tiny size, development is happening fast. The heart is beginning to form and will beat for the first time around now, the brain and spinal cord are taking shape, and the placenta is building itself to supply nutrients and oxygen for the months ahead.
What’s Developing Inside You
Week 5 is when the embryo’s nervous system kicks into high gear. The two sides of the spine are joining together to cover and protect the spinal cord, forming what’s called the neural tube. The top of this tube will become the brain; the rest becomes the spinal cord. This is one of the most critical windows in the entire pregnancy for neural development, which is why folic acid matters so much right now (more on that below).
The face is also starting to take shape, with a tiny nose and small eyes that won’t open until around 28 weeks. Blood vessels are forming, and a string of them will eventually become the umbilical cord. The placenta, still under construction, is already beginning the work of filtering nutrients in and waste out.
Symptoms You Might Notice
Some people feel noticeably different by week 5. Others feel nothing at all. Both are normal. The most common early symptoms include tender or swollen breasts, nausea (with or without vomiting), fatigue, food cravings or aversions, and needing to urinate more often. Heartburn and constipation can also show up this early.
Breast tenderness happens because of the hormonal shift that starts almost immediately after conception. Frequent urination has a different cause: your blood volume is already increasing, which sends extra fluid through the kidneys and into the bladder. That increased need to pee isn’t from the uterus pressing on the bladder yet. That comes later.
If you’re not experiencing any symptoms, that’s not a sign something is wrong. Symptom timing and intensity vary widely from person to person and even from one pregnancy to the next.
What Happens at an Ultrasound
If you have an ultrasound at 5 weeks, it will typically be transvaginal rather than abdominal, since the embryo is so small. The main thing visible at this point is the gestational sac and possibly the yolk sac, which provides early nourishment before the placenta takes over. A heartbeat is not reliably detectable yet. Most providers wait until around 6 to 7 weeks to check for a heartbeat, so don’t panic if one isn’t seen at a 5-week scan.
Pregnancy Loss Risk at This Stage
A large pooled study of over 12,000 pregnancies found that the week-specific risk of miscarriage at week 5 is around 4%. That means for every 100 pregnancies that reach the start of week 5, about 4 will end that week. This risk drops steadily with each passing week, especially once a heartbeat is confirmed. Mild cramping or light spotting can be normal in early pregnancy, but certain symptoms warrant immediate attention.
An ectopic pregnancy, where the fertilized egg implants outside the uterus (usually in a fallopian tube), can mimic early pregnancy symptoms at first. The warning signs that set it apart are pelvic pain combined with vaginal bleeding, shoulder pain, or an urge to have a bowel movement. Severe abdominal pain with bleeding, extreme lightheadedness, or fainting are emergency symptoms that need immediate care.
Why Folic Acid Matters Right Now
The neural tube closes during the first weeks of pregnancy, often before many people even know they’re pregnant. Getting enough folic acid during this window significantly reduces the risk of neural tube defects like spina bifida. The CDC recommends 400 micrograms (mcg) daily for anyone who could become pregnant, ideally starting at least one month before conception and continuing through the first trimester. If you’ve had a previous pregnancy affected by a neural tube defect, the recommended dose jumps to 4,000 mcg daily. Most prenatal vitamins contain at least 400 mcg.
Foods and Drinks to Avoid
Early pregnancy is a good time to tighten up food safety habits, since your immune system shifts during pregnancy make you more vulnerable to certain infections. The key things to skip:
- High-mercury fish: swordfish, shark, king mackerel, marlin, bigeye tuna, orange roughy, and tilefish.
- Raw or undercooked seafood: sushi, sashimi, ceviche, raw oysters, and smoked seafood like lox.
- Undercooked meat and eggs: cook all meat and poultry thoroughly, heat hot dogs and deli meats until steaming, and avoid foods made with raw eggs like homemade Caesar dressing, raw cookie dough, or tiramisu.
- Soft cheeses: brie, feta, and blue cheese unless the label confirms they’re made with pasteurized milk.
- Unpasteurized products: raw milk, unpasteurized juice or cider.
- Raw sprouts: alfalfa, clover, radish, and mung bean sprouts can harbor bacteria that are difficult to wash off.
For caffeine, the general guideline is to stay under 200 mg per day. A standard 8-ounce cup of brewed coffee has about 95 mg, brewed tea about 47 mg, and a 12-ounce cola around 33 mg. So one cup of coffee a day typically fits within the limit.
Your First Prenatal Appointment
Most providers schedule the first prenatal visit sometime between weeks 6 and 10, but you should call to book it as soon as you get a positive test. At that first visit, expect bloodwork to check your blood type (including Rh factor), hemoglobin levels, and immunity to infections like rubella and chickenpox. You’ll also be screened for hepatitis B, syphilis, gonorrhea, chlamydia, and HIV. A urine sample checks for bladder or urinary tract infections. Depending on your history, you may get a physical exam including a breast exam, pelvic exam, and possibly a Pap test.
Your provider will also typically discuss prenatal genetic screening options, which may include ultrasound or blood tests to check for conditions like Down syndrome. These screenings are optional, and the timing varies, with some happening later in the first trimester or early in the second.