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  1. Home / Pregnancy / Week-by-Week / 3 Weeks Pregnant
Spyglass shows a poppy seed
37 Weeks to go

3 Weeks Pregnant

Your baby is as big as a poppy seed.

Dr. Kuzmina, Alona
byDr. Kuzmina, Alona Updated: May 30, 2021

In This Article

    Three weeks of pregnancy is nearing one month. It is still the beginning of the first trimester.

    Week 3: How is your baby doing now:

    Your fetus is still an embryo – a cluster of cells that are quickly multiplying and growing. It is still a very small ball of cells (called a blastocyst), but it is already the basis for the future baby, placenta and umbilical cord.

    The blastocyst starts to develop three different cell layers: the ectoderm, which will turn into nervous system, hair and skin; the endoderm, which will develop thyroid, liver, pancreas and gastrointestinal tract; and the mesoderm, which will form baby’s skeleton, muscles, blood system and urogenital system.

    This week your blastocyst starts the journey from the ovary via the fallopian tube to your uterus. The follicle (fluid-filled sac) produces a new yellow body of cells (called the corpus luteum) that stays inside of the egg. The corpus luteum starts to produce the pregnancy hormones (both estrogen and progesterone) and feeds your embryo until about 10 weeks, when the placenta will take over. This part of the journey will take about a week.

    The internal lining of the fallopian tube is covered with special hair-like structures (cilia) that are moving and creating the flow that pushes the blastocyst toward the uterine cavity. This is a time that can result in a serious complication – tubal (ectopic) pregnancy, where the blastocyst implants outside of the uterus. This type of pregnancy can survive in the tube for a few weeks, but due to lack of necessary blood supply, ultimately the embryo is not viable and will not survive.

    Signs and symptoms of ectopic pregnancy include: sharp abdominal cramps, low abdominal pain on one side of the body, dizziness, weakness, pain in rectum, upset stomach, vomiting, light vaginal bleeding, shoulder or neck pain. Usually these appear around the sixth to eighth week of pregnancy, but you should be aware of these symptoms in advance and seek medical attention as soon as you feel any of the above symptoms.

    Our goal here is to be prepared, not scared. Keep open communications with your doctor, and we hope for only the best on your journey!

    Week 3: How is your Baby looks like on an Obstetrical Ultrasound:

    There is still no detectable fetus on even a transvaginal ultrasound. TOO EARLY!

    Week 6: Your Body changes:

    • You might start to experience changes in your sense of smell. This is caused by the hormones of pregnancy – estrogen and chorionic gonadotropin. Every good and bad smell gets magnified and potentially irritating. This could worsen your morning sickness.
    • The corpus luteum is producing more bHCG – soon you will be able to try a pregnancy test. A home pregnancy test is done by using a small amount of urine, that can contain the pregnancy hormone. A blood pregnancy test can detect even lower amounts of bHCG and is 99% accurate.
    • You might feel nothing different yet, but the main clue will be the late period and amenorrhea (no periods).

    Week 3: Tips to you

    1. To better deal with some of the intense smells around you – try to stay away from spicy and smelly foods, use a microwave to heat your food (it absorbs the smells while heating), ask your family and relatives to stop using intense colognes and perfumes, switch to unscented personal care products (shampoos, soaps, laundry detergents, etc).
    2. Watch your diet closely:
      • Increase calcium and iron consumption (baby will need lots of calcium to build the bones soon). They are essential for the nervous system and muscles, especially the heart. Try to have at least four servings of yogurt, hard cheese or calcium fortified cereal. If your body doesn’t have enough – your baby will need to absorb the calcium from your own body leading to brittle nails, loss of hair, dental/tooth problems and less strong bones.
      • To be able to absorb iron you will have to increase the amount of vitamin C in your diet. Iron is important for oxygen transport, and your body now has increased need due to the volume expansion of pregnancy. So, start incorporating foods into your routine like strawberries, asparagus, kiwi, peppers, tomatoes, spinach, beef and dried fruits.
      • Eat plenty of protein – 2-3 servings a day will help build your baby’s growing body. Choose some lean beef or chicken, fish, cottage cheese, eggs or legumes.
      • Do not forget about your daily pregnancy vitamins!
    3. Do not rush to do the pregnancy test! The test will be more accurate after the time of your missed period – this is when you will start to produce enough of the pregnancy hormone (bHCG) that is detectable by the pregnancy test. If you are late and the test is negative – repeat it in a few days. The blood pregnancy test that you can do at the laboratory (ordered by your doctor only) is more accurate and can detect the rise in bHCG earlier.
    4. Mood swings are normal. They are due to hormonal changes. Try to relax and take things one at a time, this is a naturally overwhelming process that affects everyone. What better time to try some mindfulness activities like meditating, breathing exercises, or stretching/yoga? Try to talk to somebody you trust about your feelings, fears, and concerns (and of course, about the upcoming joys too!).

    Dr. Kuzmina, Alona
    Dr. Kuzmina, Alona

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    View Sources
    • American College of Obstetricians and Gynecologists (ACOG)

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