4 Weeks Pregnant: Embryo (Fetus) and Symptoms

Week 4 is around the time of your expected menstrual period, and you might be feeling jittery because your period has not yet come and you’re thinking to yourself, “I might be pregnant!” Although there are no noticeable physical changes, the embryo (which will be called a fetus starting from the end of Week 10 of pregnancy) in your tummy is slowly but surely growing day-by-day. So what are the physical conditions of and changes in the pregnant woman and the embryo?

4 Weeks Pregnant: Test kits can detect pregnancy

pregnancy test kit

Over-the-counter pregnancy test kits react to the hormone hCG (human chorionic gonadotropin) in urine to produce results. Generally, for pregnancy test kits which can be used a week after the expected menstrual date, if an hCG level of 50mIU/ml (milli-international units per liter) is detected, there will be a positive result.

For pregnancy test kits which are more sensitive and which can be used from the first day of the expected menstrual period, pregnancy can be detected even if there is only an hCG level of 25mIU/ml present. After getting a positive response from the pregnancy test kit, the presence of the embryo in the uterus can be confirmed at the earliest via a sonogram during Week 4, but is generally confirmed in Week 5 to 6.

However, in the case of an ectopic pregnancy (when the embryo develops outside the womb, typically in a fallopian tube), a pregnancy test kit will give a positive result but the ultrasound scans will produce no results. If over-the-counter pregnancy test kits give you a positive result, it is best to follow up with a visit to your ob-gyn as soon as possible.

An ectopic pregnancy can be life-threatening, so take note not to overlook signs of physical change in your body until you are sure about whether the gestational sac is there or not.

Symptoms: Abdominal pain and bleeding

pregnancy pain

The changes taking place during Week 4 of pregnancy are called ”very early signs of pregnancy,” and symptoms like abdominal or lower abdominal pain might appear. This occurs because the spike in hCG secreted causes the corpus luteum to be stimulated, which in turn causes the swelling of the ovaries and the development of the placenta.

In addition to this, pregnancy increases the amount of estrogen (follicle-stimulating hormone) secreted, which causes the alveoli (mammary glands) to create breast milk. Breast milk begins to pass through lactiferous ducts, makes the breast swell and also causes some pregnant women to feel feverish.

Also, pregnancy causes an increase in the amount of progesterone (steroid hormone secreted by the corpus luteum) secreted, and this might make you feel drowsy, and cause you to fall asleep even in the middle of the day. As the “very early pregnancy signs” are usually similar to symptoms which appear that of those before and during menstruation, many women do not yet realize that they are pregnant.

Symptoms: Morning sickness

woman morning sickness

Morning sickness is one of the many physiological phenomena associated with the early stage of pregnancy. Other early signs of pregnancy include a variety of symptoms like nausea, feeling sick to your stomach, constipation, diarrhea, drowsiness, low-spiritedness, or headaches.

The severity of these symptoms differ from individual to individual, but in general, morning sickness begins from around Week 4 to 6. More than half of pregnant women experience morning sickness, while some don’t experience it at all.

You might be worried that the vomiting and not being able to have proper meals will adversely affect your baby’s nutrition. However, until the placenta is completely formed, baby will not be affected even if your dietary lifestyle all goes awry. You might want to try adopting the motto “eat what you can, when you can, how much you can” and see if it helps combat your morning sickness.

4 Weeks Pregnant: Embryo (Fetus) in your belly is 1.5-10 mm long

heart fetus

The embryo only starts resembling a human when it reaches the length of about 1.5 to 10 mm long. It resembles a fish more with its tail and gills. Although ultrasound scans in Week 4 can show you the gestational sac – the sac in which the baby is in – you will not be able to see your baby yet. From Week 5 or after that, you will be able to hear Baby’s heartbeat.


The fetus’ growth

● The neural tube, which will become the brain and spinal cord, starts to form.
● The tubular heart (primitive heart tube) is starting to form and separates into the right and left ventricles.
● Protrusions and indentations that will become eyes, ears, nose, and mouth appear, while buds that will become legs and hands start appearing
● Respiratory organs called bronchi (bronchiole, airway passages) start appearing
● The placenta starts to form

4 Weeks Pregnant: Take note of abnormal bleeding

woman note

When you’re pregnant, the uterine mucosa (also known as the endometrium, or lining inside the uterus) grows into a thick layer full of blood vessels, and bleeding is a common sign. In the early stage of pregnancy, 20% of pregnant mothers experience bleeding. You might see light brownish or blackish blood, but that is usually just the remnants from the previous bleeding.

There is nothing to worry about, so try to keep calm and remember everything will be fine. However, if the discharge is dark brown, or if a heavy flow of fresh blood is discharged, it’s possible that a miscarriage has taken place. It’s best that you head to the hospital for a check-up.

4 Weeks Pregnant: Miscarriage occurs easily

ob-gyn check

Pregnancy in the early stage is a period when problems in both the mother’s body and in the fetus arise easily, and this means that a high proportion of early pregnancy losses occur around the Week 4 period. Early stage pregnancy loss generally occurs due to abnormalities in the fetus’ chromosomes and genes preventing normal cell division from taking place. This prevents the embryo from continuing its development.

It is rare for the mother’s body to cause pregnancy loss in the early stage, and although one might take precautions and be careful, it is difficult to prevent a miscarriage in early stage pregnancy. The possibility of experiencing a pregnancy loss is a high percentage of 10 to 15%. Try to take note of the slight changes in your body, and go to your ob-gyn immediately if you need some advice.

Try calculating your Estimated Delivery Date (EDD)


Your Estimated Delivery Date (EDD) is the day you will most likely deliver your baby. Ultrasound scans from Week 8-11 at the hospital will give you the measurements of your baby, which is helpful in calculating your EDD. If you know when the “first day of your last menstrual period” was, you will be able to come up with a rough estimate of your EDD by yourself.

There are two ways of calculating your EDD. The first method is to subtract 3 months from the first day of your last menstrual period, then add 7 days. For example, if your first day of your last period falls on the 26th of January, count backwards 3 months and you will get the 26th of October. After adding 7 days, you will arrive at your EDD – 2nd November.

The second method of calculating your EDD, on the assumption that your cycle is 28 days, is to set the first day of your last menstrual period as Day 0, and then add 280 days to it.

How about giving one of these two methods a go? If you calculate your EDD and estimate when you’ll be able to meet your baby, each and every day up till then will be a very exciting countdown.