This week your baby is a rapidly dividing ball of cells called a blastocyst. MedlinePlus describes it as "a ball of cells called a blastocyst", made up of "an inner group of cells with an outer shell", where the inner group becomes the embryo and the outer group becomes the structures that nourish it. [1]
Once the fertilized egg attaches to the uterine wall, the placenta starts making a hormone called human chorionic gonadotropin (hCG). MedlinePlus writes that hCG "is made by the placenta", that "The placenta starts making hCG after a fertilized egg attaches to the inside wall of your uterus", and that levels then continue to rise. [1]
A missed period is one of the most common early signs of pregnancy. MedlinePlus lists among the other common signs swollen and tender breasts, fatigue, needing to pee more often, nausea and vomiting, and feeling bloated. [2]
You can also be pregnant without many typical symptoms. MedlinePlus writes that home urine tests are 97 to 99 percent accurate when done a week or two after a missed period. So if you feel nothing much yet, that is common too. [2]
Some people notice light spotting known as implantation bleeding. ACOG writes that "Light bleeding or spotting can occur 1 to 2 weeks after fertilization when the fertilized egg implants in the lining of the uterus". [2]
Bleeding in the first trimester is more common than many people expect. It happens in about 15 to 25 of every 100 pregnancies, and in many cases it does not signal a serious problem. [3]
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Browse the week by week Learn libraryStart a daily prenatal vitamin now if you have not already. The CDC recommends 400 mcg of folic acid every day for anyone who can become pregnant, to help prevent serious birth defects of the brain and spine (neural tube defects). [4]
Timing is the reason this matters this week. Because neural tube defects form very early in pregnancy, the CDC advises taking 400 mcg of folic acid starting at least one month before pregnancy and continuing through the first three months. [5]
There is no known safe amount of alcohol during pregnancy and no safe time to drink. All types, including wine, beer, and liquor, can harm the baby, and it is never too late to stop. [6]
Smoking during pregnancy raises the risk of preterm delivery, restricted fetal growth, and infant death. Quitting at any point during pregnancy helps protect both you and your baby. [7]
You do not have to give up coffee entirely. ACOG states that moderate caffeine of less than 200 mg per day, about one 12 ounce cup of coffee, does not appear to be a major contributing factor in miscarriage or preterm birth. [8]
At 4 weeks, mild cramping and light spotting are common. Most of what you feel right now is normal. A few signs deserve a call, so you never have to wonder. [3]
Sharp or severe pain on one side of your lower belly, especially with dizziness, feeling faint, or pain in the tip of your shoulder: ACOG says that with sudden severe pain, shoulder pain or weakness you should go to an emergency room. [9]
Bleeding that soaks through a pad, or heavy bleeding with cramping: call your provider today. If the bleeding is heavy and you also feel faint or the pain is severe, go to emergency care now. [10]
Any vaginal bleeding during pregnancy is worth a call. ACOG advises contacting your ob-gyn about it so the cause can be checked. [3]
A temperature of 100.4 F (38 C) or higher, chills, or pain when you pee: call your provider today. [11]
Vomiting so often that you cannot keep liquids down, or signs of dehydration such as dark urine, dizziness, or peeing much less than usual: call your provider today. [12]
Leelalu is education, not medical care. Nothing here is a diagnosis. For anything on this list, or any symptom that worries you, contact your provider. If it feels like an emergency, call 911.
Your next step is booking care. March of Dimes advises calling your provider for your first prenatal checkup as soon as you know you are pregnant, with routine checkups then scheduled about every 4 weeks through week 28. [14]
As you move toward week 5, it helps to hold the big picture gently. Early pregnancy loss is common, occurring in about 10 percent of clinically recognized pregnancies, which means the large majority of recognized pregnancies continue. And about half of early losses come from random chromosomal differences, generally not caused by anything a parent did. [15]
Yes. You can be pregnant without many typical symptoms. MedlinePlus writes that a home urine test is 97 to 99 percent accurate a week or two after a missed period. [2]
Yes. A pregnancy test looks for hCG, which the placenta starts making after the egg attaches to the uterus, as early as about 10 days after conception. Home tests are about 97 to 99 percent accurate a week or two after a missed period, so retest in about a week if an early result is negative. [13]
This week your baby is what MedlinePlus calls a ball of cells called a blastocyst, with an inner group of cells that becomes the embryo and an outer shell that becomes the structures around it. [1]
LEELALU is education, not medicine. This page cannot diagnose or treat anything, and it never replaces your clinician. For anything on the "call your doctor" list, or anything that worries you, contact your provider. Found an error? Write to hello@leelalu.com and a person will read it. Our method: Editorial Standards.
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