6th Week Pregnancy: Baby Development, Symptoms And Ultrasound


In the sixth week, you are still in the initial phase of your pregnancy but can reach some important milestones and see your little one through the first-trimester ultrasound. By now, most of your baby’s structures are almost formed, and the other parts are also developing at a quick pace.

At six weeks, you might also experience a variety of pregnancy symptoms due to hormonal fluctuations. Continue reading this MomJunction post to know more about what happens in the sixth week and what you have to do to let the pregnancy progress smoothly.

Baby Development

At this stage, the baby continues to develop at a faster rate. Most of the organs begin to form by now.

  1. Baby’s size: The fetus is now about the size of a lentil, which is around ¼ inch (1). It is visible through the ultrasound scan when the doctor can evaluate the fetal size.
  1. Brain development: By the sixth week of pregnancy, the fetus develops the cerebral cortex, which is a part of the brain. The neurons also start to develop and form connections that are known as synapses. These connections enable communication between the neurons, and at a later stage, allow the fetus to make movements (2).
  1. Heart development: A basic heart that starts to pump blood is formed by the fifth week. Also, the four chambers in the heart are formed by now. The ultrasound at this stage monitors the fetal heart rate or cardiac activity to determine viability (3).
  1. Other developments: Some other developing features of the fetus in the sixth week of pregnancy include (4) (1).
    • The ears begin to take shape, and the ear opening is visible.
    • The salivary glands are formed in the mouth.
    • The diaphragm, which is one of the main muscles that help in breathing, is now formed.
    • Eyes start to develop and stay sealed for protection from light.
    • The limb buds begin to develop. Fingers are also formed at this stage.
    • The jaw of the baby is formed with gums and teeth buds inside.
    • The kidneys start to function, and the stomach also produces digestive juices.

As your baby develops rapidly this week, you might experience a lot of symptoms.

[ Read: 7th Week Pregnancy ]

Symptoms During Sixth Week Of Pregnancy

Besides nausea and discomfort, there are some other symptoms that you may start to experience in week six of pregnancy.

  1. Morning sickness: Most pregnant women experience nausea and vomiting during the early weeks of pregnancy. The symptoms peak between week six and declines after week 18 (5).
  1. Indigestion and heartburn: The pregnancy hormone, progesterone, is responsible for slowed digestion during pregnancy. This, in turn, could lead to indigestion and even heartburn.
  1. Fatigue: The baby’s rapid growth leads to changes in your body, which can leave you feeling tired even after resting. And this might make you cranky.
  1. Breast changes: You might experience certain changes in the breasts that tend to grow and get bigger by this week. There could be tenderness and swelling at times (6).
  1. Others: Bloating, mild headache, mood swings, and frequent urination are some other symptoms that pregnant women might experience at week six.

Continue reading the post as we tell you about the sixth-week ultrasound next.

Ultrasound In The Sixth Week

The first scan of the first trimester is ideally scheduled in the sixth week. This ultrasound helps with the early diagnosis of the fetus and to detect any abnormalities (7).

  1. Fetal heart rate: The ultrasound helps to monitor the fetal heart by diagnosing the number of beats per minute. The heart rate usually tends to increase between the sixth week and the ninth week, although it might get slower later.
  1. Gestational age: The first-trimester ultrasound also helps to know the fetal pole (mass of cells) and crown-rump length (head to butt) of the fetus. These figures, in turn, help determine the gestational age.
  1. Twins or multiples: The sixth-week ultrasound also helps detect if it is a single fetus, twins, or multiples.
  1. Location of the pregnancy that it is normal inside the uterus or abnormal in place.

It also helps to know if there are any complexities with the development of the fetus.

Tips To Remember In Week Six Of Pregnancy

  1. Doctor’s visit: If you have missed the doctor’s appointment in the fifth week, now is the time to do it. Get your blood pressure, heart rate, and weight checked. If you’ve had a check-up the previous week, you can visit for the first-trimester ultrasound this week.
  1. Pregnancy diet plan: Based on your health, the doctor may create a pregnancy diet plan for you. The focus should be on a healthier menu even if you crave junk or sugary foods. After all, your health is connected to your baby’s health. Also, drink enough water to keep constipation problems at bay.
  1. Light exercise: Even though you feel tired pretty soon, it is essential that you engage in some light exercises such as walking. This will help you to stay active and keep your body fit for more changes. Always ask your doctor about it.
  1. Small meals and naps: To deal with nausea, vomiting, and tiredness, you need to eat your meals in small quantities and take frequent naps. These changes in your lifestyle will help you deal better with early pregnancy symptoms.

[ Read: 8th Week Pregnancy ]

Talk to your doctor and clear any doubts about your health, prenatal vitamins, diet, allergies, or medications. Note that it is normal to go through physical and emotional changes in the sixth week of pregnancy. Try to stay relaxed, keep negative thoughts away, and take care of yourself to enjoy a smooth pregnancy.


MomJunction's articles are written after analyzing the research works of expert authors and institutions. Our references consist of resources established by authorities in their respective fields. You can learn more about the authenticity of the information we present in our editorial policy.
1. Fetal Growth And Development; South Dakota Department of Health
2. Prenatal Form and Function – The Making of an Earth Suit (5 to 6 weeks); The Endowment For Human Development
3. E. R. Ranch et al.; Embryonic heart rate as a predictor of first-trimester pregnancy loss in infertility patients after in vitro fertilization; Fertility and Sterility (2009)
4. Fetal Development; Lambton Right to Life
5. Morning sickness is Mother Nature’s way of protecting mothers and their unborn, Cornell biologists find; Cornell Chronicle (2000)
6. Your Body Before Pregnancy; Childbirth Connection
7. G. M. Graham III; Ultrasound Evaluation of Pregnancy in the First Trimester; Donald School Journal of Ultrasound in Obstetrics and Gynecology (2010)


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shreeja pillai

Shreeja holds a postgraduate degree in Chemistry and diploma in Drug Regulatory Affairs. Before joining MomJunction, she worked as a research analyst with a leading multinational pharmaceutical company. Her interest in the field of medical research has developed her passion for writing research-based articles. As a writer, she aims at providing informative articles on health and pharma, especially related to... more