5th – Fifth week of pregnancy

By the fifth week of pregnancy, the heart and nervous system of the embryo begin to develop. And this is also the time when you may start to feel some slight change within you.

From the beginning of its development to today, therefore in the previous three weeks of pregnancy, the embryo has increased in size by 40%, (remember that, according to the convention adopted , in the first two weeks the embryo had not yet been conceived ).

As for you, the pregnant woman, hormones may cause unexpected mood swings. You could, for example, go from laughing to crying in an instant. This is the time when you may even begin to feel some slight changes within you.

The development of the embryo during the 5th week of pregnancy

The three embryonic and extra-embryonic tissue “sheets” – which we know were formed in week 4  – continue to differentiate.

The three layers – ectoderm , endoderm, mesoderm – begin to develop in different organs and in different body parts. Let’s examine them in more detail.

Ectoderm.  The ectoderm forms the neural tube (a structure that is present in embryos) that will evolve into the brain, nerves, spinal cord, and vertebral column.

The somites (body segments in the vertebrate embryo) begin to develop into what will eventually be skeletal muscles, cartilage, tendons, and dermis.

Mesoderm. It is the middle layer of the three embryonic tissue layers: the circulatory system and the heart of the embryo begin to develop at the same time.

The baby’s first red blood cells also begin to develop at this stage.

However, the yolk sac still takes care of the baby’s needs, as the baby’s heart is not yet evolved enough to function on its own.

Endoderm. It is the innermost germ layer: it evolves into the lungs, intestines, a rudimentary urinary system, the thyroid gland, pancreas and liver.

Blood vessels – roughly speaking – form a connection between you and your baby which will then develop into the umbilical cord.

The primitive umbilical cord and the placenta provide all the nourishment and oxygen that the embryo needs, while the amniotic sac continues to grow.

During this stage of gestation, the embryo is about the size of an orange seed (about 2 mm long), while its shape resembles that of a tadpole, with an enormous head and a body that has yet to be defined.

Your body

Over the course of this week, the levels of estrogen, progesterone and hCG continue to rise, which causes various symptoms. As in the previous week, your volemia (blood volume) will continue to increase, causing your kidneys and heart to work harder.

This is when most women first notice their periods are late, and then decide to take a home pregnancy test . At this stage home pregnancy tests can already give positive results as hCG levels normally become high enough to be detected in the urine. However, in case of low hormone production, these tests could also give negative results. In pregnancy, hormone levels are usually at their highest when you wake up in the morning, so that’s the best time to take a pregnancy test. Your doctor may also recommend a blood test to determine hCG levels, as this helps to understand the health of the embryo.

While the bodily changes are enough to make you aware that your unborn baby is growing, it’s still too early to start showing a bump.

The ultrasound in the fifth week of pregnancy

To confirm the presence of the embryo in this period, transvaginal ultrasounds are more efficient than transabdominal ones . During a transvaginal ultrasound, a lubricated rod is inserted into the vagina and images are translated onto a screen. It shouldn’t be painful, but it might be a little uncomfortable.

However, an ultrasound done in the fifth week may also fail to detect the baby’s heartbeat, as it is still too low to be heard.

Don’t worry if you can’t see your baby, these days the embryo is the size of an orange seed, about 2 millimeters. The only things you’ll likely be able to see via ultrasound are the yolk sac and gestational sac.

The sonographer may be able to point to the embryo, which at this stage is probably a tiny white curled object. Surrounding the embryo is the yolk sac, which will look like a small white circle. The yolk sac nourishes the embryo and also helps produce blood cells during the early stages of pregnancy.

The yolk sac is surrounded by a larger black area, the gestational sac. The gestational sac contains amniotic fluid and surrounds the embryo.

You may be able to see the flicker of a small heartbeat, but again, don’t worry if the sonographer can’t see it yet—it’s still very early.

The symptoms that usually occur during the fifth week

The classic symptoms of procreation in progress begin to become more important starting this week.

However, there’s nothing to worry about if you still don’t have symptoms.

The earliest symptoms of pregnancy consist of: morning sickness and vomiting, headache , breast tenderness, bloating, heartburn, constipation/diarrhea, abdominal tightness, bloating and indigestion.

Additional symptoms — which may be persistent, or which may come and go frequently — include:

  • from a better sense of smell;
  • by a continuous feeling of fullness or heaviness (caused by increased blood flow to the uterus and pelvic congestion);
  • feel dizzy and faint (these feelings may get worse if you have low blood sugar, or if you haven’t eaten in hours);
  • from nervousness;
  • shortness of breath (more common in twin pregnancies
  • from food cravings or aversions;
  • from tiredness or fatigue (caused by hormonal changes and growth of the placenta);
  • from cramps, similar to menstrual cramps, and pain in the lower back;
  • from night sweats;
  • frequent urination (due to increased blood flow to the kidneys and pelvic region);
  • from an excess of saliva (caused by the functioning of pregnancy hormones);
  • from vaginal discharge or brown specks (blood from the implant);
  • from transparent and gelatinous vaginal secretions;
  • from changes or mood swings;
  • from excessive thirst;
  • from cramps in the legs and feet;
  • from a slight pain in the joints and groin;
  • from pregnancy rhinitis, caused by a stuffy/runny nose (due to high estrogen levels);
  • by alterations in the perception of the taste buds present in your mouth, caused by a hormonal change.

Twin pregnancies , compared to singleton pregnancies, produce higher levels of pregnancy hormones.

So morning sickness may be more intense in women carrying twins.

The possible congenital defects of the embryo

A congenital disorder is defined as a disorder that originates before birth. 6 ]

The most common   congenital defects – cleft lip , spina bifida, anencephaly, gastroschisis, etc. – including those involving the neural tube develop during the first semester. 6 ]

Any abnormality in the tail of the neural tube can cause spina bifida. While abnormalities in the head can affect skull formation, leading to anencephaly.

It is estimated that one in twenty children born (including those who would have been born if the pregnancy had not been terminated after prenatal diagnosis) is affected by a birth defect. 5 ]

For completeness, we recall that Down syndrome is not a congenital defect, but is due to a chromosomal anomaly, which was already present in the parents’ gametes.

Possible complications of pregnancy

Try to look out for the following symptoms, as they may indicate serious complications, such as an ectopic pregnancy ,  miscarriage , or bacterial infection:

  • severe vaginal bleeding;
  • leakage of blood clots;
  • fever;
  • extreme dehydration (may indicate  gestational diabetes );
  • severe lower abdominal pain or cramping (left side, or right side);
  • extreme dizziness;
  • extreme depression (lasting for more than two weeks).

Some things to know about the 5th week of pregnancy

  • Your baby’s heart, which has almost doubled in size in the last few days, beats: now its beat is very fast, twice that of an adult.
  • During this stage of pregnancy, the increase in the hormones estrogen and progesterone (a steroid hormone belonging to the group of progestin hormones ) which are going up, will make your hair and skin shinier and more beautiful.
  • In this period, early ultrasounds can diagnose multiple gestational sacs: from this moment on, you can know for sure whether or not you are expecting twins.

Some things and some useful advice for a peaceful expectation and a healthy baby

  • During this period you should drink at least a liter and a half of water a day to rehydrate the body, to reduce nausea and protect the kidneys which work twice as hard during pregnancy.
  • Follow a diet with lots of fruits rich in vitamin C, such as oranges, kiwis and black currants, as vitamin C helps your baby’s cells grow rapidly.
  • Continue to take  “prenatal” vitamins containing vitamin D and folic acid.
    • Folic acid (naturally present mainly in leafy vegetables such as spinach, beets and kale) is important for the correct development of your baby’s nervous system.
    • If you weren’t already taking it, it’s important that you also take it as a tablet to be taken daily.
  • Stop taking drinks containing caffeine and  alcohol.
  • Stop smoking.
  • Avoid consuming large quantities of big fish such as tuna, swordfish, shark because they contain a higher amount of mercury.
  • Choose organic farming and production products: pesticides, hormones, metals and other substances represent potential dangers that we can find in many foods.
  • Unless you have a high-risk pregnancy, continue jogging if you used to do it daily before conception: jogging 3-4 days a week is “safe”.
  • If you can, and if you like it, swim every day to keep yourself in good physical shape.
  • inform the healthcare professional about your pregnancy before undergoing x-ray examinations for any problems (for example for dental treatment).
  • Tell your doctor about any medicines you take.
  • Until at least the 13-15th week , avoid long journeys: if necessary, choose the most comfortable means of transport.
  • Ginger intake seems to have beneficial effects on the feeling of nausea. 7 ] However, some experts warn that high doses of this herb could increase the risk of miscarriage. Although quantities of ginger less than 1500 mg are not considered dangerous, we advise you to consult your doctor before taking this root during pregnancy. 8 ]
  • chew sugarless gum to manage the symptom of excessive salivation.

Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.

She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform, Maternicity.com.

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