12th – Twelfth week of pregnancy

12 week of pregnancy

In this article, we’ll tell you what you need to know about your baby’s development, about changes in your body, and about (if any) unusual symptoms you’ll need to look out for this week. However, know that these pages are purely informative and informative, and do not replace medical advice.

The development of the fetus at the 12th week

the development of his nervous system

The period between the twelfth and twenty-second gestational weeks is vital for the development of the brain of the fetus: in the twelfth week, the pituitary gland begins to produce hormones, while the nerve cells of its brain develop and multiply rapidly, at the rate of 15 million per hour .

the development of its internal organs

From the 11th week, the muscular tunic is present , which in the future will be responsible for bowel movements, and with the 12th week, the development of the intestinal glands begins. In a normal pregnancy, the volume of the heart and lungs increases from this week until it reaches its maximum during the 32nd week. With the ultrasound, the kidneys are already visible and the bladder begins to be visible. During this week the first ones measure about 1 cm in length and will grow to 2.7 cm during the 20th week.

the development of the limbs

The hands and feet are fully developed: the child is already able to bend the elbow. The preferred arm posture at 12 weeks is with the elbow flexed and the wrist and fingers extended. During this week, he may also start sucking his thumb which means his reflexes are starting to develop. A 2005 study found that fetuses who suck their right thumb tend to become right-handed, those who suck their left thumb to become left-handed .

its outward appearance

His face already resembles that of a miniature newborn , with his eyes and ears that are almost in place, as can be seen on ultrasound scans. At 12 weeks, it may already be possible to use ultrasound to determine gender based on the angle of the genital tubercle .

the development of his bones

In this week or so, your skeletal system begins as a cartilaginous structure, which begins to ossify (become solid bone).
Your bone marrow also starts producing white blood cells to help fight infection.

its sources of nutrients

During this week, the placenta filters oxygen and all the nutrients necessary for proper fetal growth.

the size of the fetus

In this week, the baby is about 5 cm long and weighs, more or less, 14 grams: it is about the size of a plum.

The woman’s body this week

The pressure on your bladder gradually decreases, as the uterus begins to lift out of your pelvis. Your belly now allows more room for the uterus to grow: in fact, your doctor can already feel it – in the lower part of the abdomen, just above the pubis – at the end (called the fundus).

Usually, expectant mothers don’t show enough of their bumps at this stage for others to notice that they are pregnant. However, the belly – always bigger – already often leads them to prefer more comfortable clothing than the usual jeans and skirts. 

Overweight women, those who have already had pregnancies, those pregnant with twins, will probably start exhibiting their baby bump before the others. This happens because your previous pregnancy may have stretched your stomach muscles and these muscles may not have returned to their original size. Due to this change, a baby bump may appear sooner.

The ultrasound at the 12th week

Ecografia alla 12-14 settimana di gravidanza. Fonte: Ackerman, Sandra. The Development and Shaping of the Brain. National Academies Press (US), 1992. https://www.ncbi.nlm.nih.gov/books/NBK234146/.

Most women have their first ultrasound in the twelfth week. As we have seen above, an ultrasound image could identify the sex of your baby this week But – as it is early in this phase – the identification could also turn out to be incorrect .

The ultrasound will also show the fetus stretching, kicking, rolling over in the uterus. But he’s still too small for you to feel his movements. It will be necessary to wait until the twentieth week to be able to think of hearing them from the outside as well.

The tests in the 12th week

Some blood tests may have already been done at your prenatal checkup to determine your risk for genetic disorders such as Down syndrome .(5) This week, your doctor may order you to have a nuchal translucency scan , which consists of in measuring fluid levels behind the baby’s neck for the purpose of detecting fetal heart abnormalities. It is a decidedly accurate test, which diagnoses about 75% of cases of anomalies . Other prenatal screening tests, such as amniocentesis and CVS, may be done later, over a few weeks, to confirm any fetal abnormalities. (6)

Symptoms at 12 weeks

You may notice an increase in your energy levels this week. while frequent urination and morning sickness are starting to subside. However, it would also be perfectly normal if – due to the increase in pregnancy hormone levels – you still continue to experience tiredness, nausea, bloating, bloating, heartburn , and indigestion.

Other common 12th week symptoms consist of:

  • blurry vision;
  • excessive salivation;
  • flatulence;
  • migraine and dizziness;
  • pain in the abdomen and back in the upper and/or lower part;
  • joint and hip pain;
  • an increased appetite now that you’re about to enter the second trimester of your pregnancy . For the second trimester the additional requirement is about 400 kcal. This slight increase in daily energy also covers the needs of the fetus, allowing normal development of the child and avoiding affecting the maternal reserves of nutrients; 
  • depression and mood changes.
  • an increase in vaginal secretions, and this due to pregnancy hormones and water retention;
  • dry itchy skin, especially around the expanding belly and around the breasts
  • sleep disturbances (insomnia);
  • a pain in the round ligament of the uterus and in the pelvis (due to the growing uterus);
  • areolas  (the circular pigmented areas surrounding the nipple) darker,
  • dark, irregular marks on the neck and face (melasma, known as the “mask of pregnancy”);
  • the appearance of a dark vertical line ( linea nigra
  • a slight shortness of breath;

Symptoms to pay attention to

The symptoms to watch out for are pretty much the same as last week. Among these, those that should most alarm are given:

  • a severe headache, with or without symptoms such as blurry vision, sudden swelling of the hands and feet and chest pain (could be signs of pre-eclampsia);
  • severe bleeding together with severe abdominal and back pain, or cramps (could be signs of a miscarriage or ectopic pregnancy
  • by extremely blurry vision (this could indicate high blood pressure or gestational diabetes
  • from fever (more than 38° degrees) that cannot be brought down;
  • from odorless and weak, clear or straw-colored secretions (they could indicate leakage of amniotic fluid);
  • a strong and frequent urge to urinate, together with a painful or burning sensation when urinating (could indicate bacterial urinary tract infections)
  • severe diarrhea or nausea with vomiting more than 3-4 times a day (this increases the risk of losing weight or dehydration)
  • severe back pain along with urine leakage, and pain when urinating (may indicate uterine retroflexion).

Useful advice, for women and children

  • follow a “routine” of light physical exercises, or sign up for a prenatal yoga class to prepare your body for the upcoming changes. Women who were physically active before pregnancy with an uncomplicated pregnancy can undertake high-intensity aerobic activity without adverse effects.
  • have – preferably – smaller meals and snacks, instead of three large main meals;
  • drink plenty of fluids to stay well hydrated by avoiding carbonated drinks, alcohol and minimizing caffeine;
  • drink liquids before or after meals, rather than during them;
  • avoid consuming excessive salt and prefer the iodized one;
  • follow a healthy diet, rich in calcium, protein and vitamins, in order to meet the nutritional needs of you and your child;
  • in case you have dry and itchy skin, consult your doctor about the fact that you can use moisturizing products;
  • avoid undergoing x-rays, unless absolutely necessary, so as to protect the child from harmful radiation;
  • avoid jerky movements and actions that could harm the child such as riding a bike, jogging and riding a roller coaster;
  • always pay attention to your hygiene and oral health. Existing scientific evidence underlines the association between the presence and severity of gum infections and premature delivery, fetal growth retardation, spontaneous abortion, pre-eclampsia;

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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