Amniocentesis – What is it, when to do it and how it is done

Amniocentesis is an exam that is done in pregnancy to discover certain diseases in the baby , such as Down syndrome , but it is not a routine exam, because it carries some risks. Because of its purpose, it is categorized as a diagnostic test, to confirm suspicions. Also called a “villus biopsy,” the test consists of taking a sample of the amniotic fluid from the uterus and examining it. It is only indicated in cases of changes in routine exams, such as morphological ultrasound , of the first trimester , or non-invasive prenatal diagnosis.

What is Amniotic Fluid?

The amniotic fluid is inside the famous “water bag” that breaks when the baby is born. This bag can be explained as a liquid-filled membrane, in the form of a bag (the amnion), that “keeps” the baby during pregnancy. The volume of liquid inside the bag increases according to the baby’s development. In general, the 28th week of pregnancy is usually the moment when the liquid reaches its limit, with the volume around one liter.

The importance of amniotic fluid is to cushion the blows or other trauma that the woman may suffer in the belly, also preventing very strong variations in temperature. This protects the developing fetus , and keeps it warm: two fundamental things for its normal development. In addition, later on, the amniotic fluid allows for greater mobility of the baby within the uterus, which strengthens its muscles and forming bones.

The liquid contains several substances and also fetal cells, with the same DNA as the baby, and some microorganisms. Therefore, this material can clarify many doubts about the baby’s health.

What Diseases Does Amniocentesis Detect?

Usually, the examination of the amniotic fluid is to diagnose genetic diseases or neurological malformations . The types of disease that the test can identify are:

  • Chromosomal changes, such as Down Syndrome, Edward Syndrome, Patau Syndrome, Turner Syndrome or Klinefelter Syndrome;
  • Congenital diseases in the neural tube, such as Spina Bifida and Anencephaly;
  • Hereditary blood disorders, such as sickle cell anemia , thalassemia and hemophilia;
  • Cystic fibrosis ;
  • Muscular dystrophy

Other information that the amniocentesis can reveal, but which can also be diagnosed in other less invasive ways, is the sex of the baby, if there is a Rh factor incompatibility between the mother and child (when the baby blood is Rh positive and that of the mother , Rh negative), or also if there is an infection. It is also possible to determine the child’s paternity before birth by DNA testing in amniotic fluid, however, the test is not usually used for this purpose.

There are still other suspicions of diseases of formation in the baby that cannot be detected by amniocentesis, but by more detailed ultrasounds , such as the case of cleft lip .

When to Do Amniocentesis?

The amniocentesis exam is indicated by the doctor when changes in exams of early pregnancy occur , added by risks presented by family history, that is, when there are cases of congenital or genetic abnormalities in the mother or father’s family. Amniocentesis should be performed after the 15th week of pregnancy . That’s because, as this week starts the second trimester, the amniotic fluid already has enough volume inside the uterus so that doctors can take an adequate sample with less risk of miscarriage or problems with the baby’s development.

There are some signs and risk factors that can help a doctor suspect problems with the baby’s formation and know when to perform amniocentesis. Among the most common are:

  • Pregnancy after 35 years;
  • Changes in routine exams in the first trimester, such as blood or ultrasound;
  • Family history of genetic diseases;
  • Inadequate conditions for intrauterine growth of the fetus;

In cases of malformations, amniocentesis is, in some countries, a way of diagnosing such early problems of pregnancy and allowing an abortion in these cases. In Brazil, however, the law is not currently permissive with malformation or genetic diseases, but only in cases of anencephalic babies, or when the woman is at risk of life. The importance of the exam is, here, more restricted to the early knowledge of the family about the health problem that the child will have.

In less severe cases, prior knowledge of the baby’s clinical conditions facilitates preparation for delivery, and the family may hire a neonatal ICU team, for example, if financial conditions exist. It is also important for the psychological preparation of the family that will receive a child with special needs.

How is the Exam and Its Procedures Done?

Amniocentesis is a simple and quick exam, with an average duration of 20 minutes. It is usually done in the obstetrician’s own office.

It works like this: the examination of the amniotic fluid requires the insertion of a long and very fine needle in the abdomen, to reach the interior of the uterine cavity. The future mother remains lying down, while the doctor uses ultrasound images to orient herself and find out where the baby is and to identify the “water bag” (of amniotic fluid). After inserting the needle in the bag , the specialist draws a small amount of liquid: about two tablespoons.

There is the possibility of using local anesthesia, however, many experts believe that this is not necessary. Anyway, you can talk to your obstetrician about pre-examination concerns and the need for anesthesia. The pain felt by the prick of the needle or by the discomfort of the exam is usually mild, and depends a lot on the woman’s sensitivity . One tip to ease nervousness is to focus on your baby’s ultrasound images, not the exam itself.
See the step-by-step procedures:

  1. With the woman lying face up and the application of a gel, the doctor uses an ultrasound machine to get to know the exact location of the baby in the womb.
  2. The belly skin is sterilized with an antiseptic product .
  3. The doctor inserts the amniocentesis needle through the skin and abdominal wall until it reaches the uterine cavity and the amniotic fluid bag – just on its surface, without touching the baby, of course!
  4. small amount of this amniotic fluid is aspirated through the syringe, and the needle is finally removed from the uterus.

IMPORTANT: The ideal is to remain immobile while the needle is inserted and the amniotic fluid is extracted. Always follow your doctor’s instructions.

What takes longer is the ultrasound procedure. The puncture of the liquid itself is done in just five minutes . The doctor should check the baby’s heart and if the uterus contracts during the examination, to ensure that there is no stress caused by the invasive method.

The reported sensations are burning when the needle penetrates the skin and cramps or cramps when it reaches the uterus. At the end of the procedure, the woman may also experience mild cramping. In case of uncomfortable pain, a pain reliever may be prescribed. Experts recommend resting for at least 24 hours after the exam, and sexual activity should be suspended for seven days.

Exam Price

The cost of amniocentesis in particular, including laboratory evaluation and the medical procedure, varies from one thousand to more than two thousand reais, and may be more expensive if performed in the third trimester of pregnancy. For this reason, the most important thing is to do it in the 2nd quarter . There are some public services that offer the exam free of charge, however, it depends on the hospitals in the region where the pregnant woman lives and on her justification for doing so.

Health plans, in most cases, only partially cover the exam: in the preparation phase, consultations and ultrasound, but not the puncture procedure. This must be checked in each case.

What are the Risks?

Although amniocentesis is considered a safe test, puncture of the fluid through the needle is an invasive method, which always has risks, even if minimal. Statistics say that about 0.2% of women who undergo the test are later induced to miscarry within a week. In much rarer cases, of less than 0.01% of women, the test can cause a serious infection. And yet, there is a very rare risk, with a rate of 0.005%, of injury to the baby by the needle.

Another fact that can occur as a result of examining the amniotic fluid is a slight temporary loss of fluid through the vagina, which occurs in about 1.7% of cases. Generally, fluid loss ceases within a week without leading to further complications.

What Are the Warning Signs After the Exam?

In addition to the normal symptoms already described that may occur after the exam, such as fluid loss, a little bleeding and cramps for a few hours, it is recommended to seek immediate medical attention in the following cases:

  • More intense bleeding
  • Too much fluid leaking through the vagina
  • Uterine contractions
  • Pain in the belly or back
  • Fever above 38º
  • Chills, malaise or feeling like flu

Results of Amniocentesis

Preliminary results, in the form of molecular analysis, can be ready in 24 hours and up to 72 hours, but the complete analysis, which is called “fetal karyotype examination”, can only be obtained within two weeks. The liquid sample needs to be sent to the laboratory, where the cells will be cultured. So it is possible to take up to two weeks for enough cells to make the diagnosis sure and safe.

The first results, which are about the most common chromosomal syndromes, can serve to reassure anxious parents when the test is negative. The baby’s sex is also revealed in these preliminary results. The best thing to do while waiting is to distract the mind and not imagine with pessimism what may come.

See Also: Amniotic Fluid Loss

Website | + posts

My name is Dr. Alexis Hart I am 38 years old, I am the mother of 3 beautiful children! Different ages, different phases 16 years, 12 years and 7 years. In love with motherhood since always, I found it difficult to make my dreams come true, and also some more after I was already a mother.

Since I imagined myself as a mother, in my thoughts everything seemed to be much easier and simpler than it really was, I expected to get pregnant as soon as I wished, but it wasn’t that simple. The first pregnancy was smooth, but my daughter’s birth was very troubled. Joana was born in 2002 with a weight of 2930kg and 45cm, from a very peaceful cesarean delivery but she had already been born with congenital pneumonia due to a broken bag not treated with antibiotics even before delivery.

Dr. Alexis Hart

My name is Dr. Alexis Hart I am 38 years old, I am the mother of 3 beautiful children! Different ages, different phases 16 years, 12 years and 7 years. In love with motherhood since always, I found it difficult to make my dreams come true, and also some more after I was already a mother. Since I imagined myself as a mother, in my thoughts everything seemed to be much easier and simpler than it really was, I expected to get pregnant as soon as I wished, but it wasn’t that simple. The first pregnancy was smooth, but my daughter’s birth was very troubled. Joana was born in 2002 with a weight of 2930kg and 45cm, from a very peaceful cesarean delivery but she had already been born with congenital pneumonia due to a broken bag not treated with antibiotics even before delivery.

Leave a Reply

Your email address will not be published.