18th – Eighteenth week of pregnancy

18 week of pregnancy

The eighteenth week in the second trimester of pregnancy is a crucially important period. In fact, most of the major second trimester exams are done between the eighteenth and twenty-second week. As usual, your doctor will have to tell you which tests are necessary to evaluate the state of your child’s growth.

Baby development in the 18th week of pregnancy

The development of internal organs

Its large intestine moves towards the back wall of the abdomen and, at the same time, the various digestive glands begin to form. This is also the week in which the uterus of the female fetus completes its formation, together with the fallopian tubes.

The development of the nervous system

The eighteenth week is of crucial importance for the development of the nervous system of the fetus. Since the 12th week, the process of myelination is underway, during which the nerves are wrapped in an insulating layer (the myelin sheath) which helps nerve impulses travel faster from one neuron to another. The myelin sheath will continue even after your baby is born.

The nerves also begin to form complex connections, while the brain further specializes in sending signals to the senses of hearing, touch, smell, sight and taste.

The development of the fetus in twin pregnancies, eighteenth week

In the case of a twin pregnancy, it has been studied that twin fetuses are able to perceive each other.

In fact, an Italian study by the Universities of Turin and Parma has shown how, starting this week, the movements of fetuses are more directed towards the twin than towards themselves, showing a sort of social behavior before birth.

How big is the fetus

Now the baby measures approximately 14-15 centimeters, roughly the size of a potato, and weighs around 200 grams.

The movements of the fetus during the eighteenth week

If before you might have mistaken them for something else (like belly rumbling or bloating), now for the first time you may notice the movements of the fetus in your belly.

Most expectant mothers feel the baby’s long-awaited punches and kicks between  17  and  24 weeks , while women who already have pregnancies often recognize them earlier.

The changes in the woman’s body

In the eighteenth week of pregnancy, your belly is evident enough for everyone to feel compelled to give you advice on how to continue your pregnancy: mothers, mothers-in-law, friends, relatives, even strangers!

If you feel tight in your clothes, surely now is the right time to buy some maternity clothes.

If, on the other hand, you’re not in the shopping mood, perhaps you can simply use the looser, more comfortable clothes you already have in your wardrobe.

These, perhaps with the help of a “trouser widening band”, could allow you to save on specific clothing for the gestation period.

You are also probably gaining weight. So making the “right” food choices is as important at this stage as the “right” gain in your second trimester weight. For a woman who started her pregnancy at a normal weight, this should increase by about 5, while it is less in overweight women.

The changes that take place in your cardiovascular system during the  second trimester lead to lower than normal blood pressure.

In addition to that, the hormone relaxin  keeps the joints and muscles in the abdomen and pelvic area relaxing, which leads to pain in these areas of the body.

The ultrasound at the eighteenth week

Around this time, a detailed ultrasound (fetal morphology ultrasound) is usually done to check the health and development of the baby.

It helps your doctor identify any structural abnormalities of the fetus and the position of the placenta.

The baby is now old enough to be identified with a transabdominal ultrasound, which is used to evaluate and measure the head, abdomen, spine, femurs and limbs of the fetus.

The baby’s sex can now be determined with certainty by ultrasound.

From now on, the doctor will be able to listen to the heartbeat of the fetus with a normal stethoscope, so that Doppler ultrasound is no longer necessary.

The alpha-fetoprotein (AFP) test, also called a maternal serum screening test, may now be recommended if you haven’t already done so at  16/17  weeks.

This test measures the levels of alpha-fetoprotein in your blood and helps assess the chances that your baby may have genetic disorders.

Abnormal levels of alpha-fetoprotein in the blood require investigation with subsequent tri-testing.

Symptoms of the eighteenth week of pregnancy

Here are some of the most common symptoms that are reported in relation to the eighteenth week of gestation:

  • lightheadedness or dizziness;
  • frequent urination;
  • stretch marks;
  • increased appetite;
  • indigestion and heartburn ;
  • tiredness;
  • vene varicose;
  • bloating and bloating;
  • constipation;
  • leg cramps;
  • pain in the round ligament of the uterus;
  • coccyx pain;
  • back and joint pain when you walk, sit or lie down;
  • epistaxis (nosebleed);
  • bleeding gums (due to pregnancy hormones and increased blood flow);
  • linea nigra (a dark line that runs vertically across your abdomen);
  • appearance of dark spots on the face and other areas of the skin;
  • itchy skin rashes;
  • shortness of breath(23);
  • edema or swelling of the arms, legs, hands and feet (due to fluid retention);
  • itching, especially around the belly, back, thighs and legs;
  • runny or stuffy nose (pregnancy rhinitis);
  • milky white vaginal discharge (leucorrhoea);
  • trouble sleeping (insomnia) and strange pregnancy dreams (your brain being more active than normal is thought to be responsible; however, scientists have yet to discover the reason for this behavior)(26);
  • anxiety and mood swings.

Signs and symptoms to look out for

Particular attention should be paid in the following cases:

  • stuffy nose, accompanied by symptoms such as sore throat, coughing, sneezing, headache , fever and vomiting (could indicate flu or some similar infection);
  • thin, clear or straw-colored vaginal discharge (may indicate that you are leaking amniotic fluid);
  • vaginal itching with pain in the lower back, burning sensation when urinating or bad smelling, dark yellowish or greenish vaginal discharge (could indicate the existence of a kidney infection or candidiasis);
  • severe abdominal pain or persistent cramps;
  • constant headaches, with extreme dizziness and blurry vision (may be signs of high blood pressure);
  • extreme tiredness, accompanied by excessive thirst, nausea and changes in vision (may be signs of  gestational diabetes
  • severe diarrhea lasting more than 24 hours.

Useful tips for a peaceful pregnancy and a healthy baby

Some tips that might be helpful:

  • in your daily diet include many foods rich in calcium and vitamin D (milk, cheese, almonds, green leafy vegetables and fruits such as apples), as they are nutrients that are necessary for the ossification of the fetus and the development of its teeth;
  • avoid making sudden movements, such as getting up too quickly from a sitting position, as by lowering your already low blood pressure even further, this could lead to dizziness or fainting;
  • if you have swollen feet, use larger shoes, as the constriction of the blood vessels could lead to further problems;
  • follow an appropriate dental hygiene “routine” (using toothbrush and floss) in order to avoid having swollen and bleeding gums, which can lead to periodontal disease: when you brush your teeth, be careful not to damage gums that are already sensitive;
  • drink plenty of water to stay hydrated, and consequently to obtain improvements in certain symptoms such as leg cramps and constipation;
  • consult your doctor before taking any medicine, even over the counter such as antihistamines and antipyretics, even if you have to manage the most common symptoms;
  • drink an occasional cup of chamomile tea or peppermint tea, in order to relieve nausea and heartburn ( consult your doctor regarding – in your specific pregnancy – the safety of herbal teas);
  • when you need to rest try to lie on your side (preferably on the left), as lying on your back puts pressure on the large veins, decreasing the blood flow between the uterus and the heart;
  • enroll in a prenatal yoga class , or do light physical exercises to strengthen the pelvic floor, in order to reduce pain and discomfort;

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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