Amniotic fluid

The amniotic fluid that surrounds a fetus (unborn baby) plays a crucial role in normal development.

This clear-colored liquid cushions and protects the baby.

By the second trimester, the baby is able to breathe the fluid into the lungs and to swallow it. This promotes normal growth and development of the lungs and gastrointestinal system.

Amniotic fluid allows the baby to move around, aiding development of muscles and bones.

The amniotic sac that contains the baby forms about 12 days after conception.

Amniotic fluid immediately begins to fill the sac. In the early weeks of pregnancy, amniotic fluid consists mainly of water supplied by the mother. After about 20 weeks, fetal urine makes up most of the fluid.

Amniotic fluid also contains nutrients, hormones and disease-fighting antibodies

The amount of amniotic fluid increases until 28 to 32 weeks of pregnancy. After that time, the level of fluid generally stays constant until the baby is full term (37 to 40 weeks), when the level begins to decline.

In some pregnancies, however, there may be too little or too much amniotic fluid. • Having too little amniotic fluid is called: oligohydramnios. • Having too much amniotic fluid is called: polyhydramnios

oligohydramnios

• About 4% of pregnant women have oligohydramnios.

• It can develop at any time during pregnancy, although it is most common in the last trimester.

• Some 12 percent of women whose pregnancies last about two weeks beyond their due dates (42 weeks gestation) develop oligohydramnios, because the level of amniotic fluid tends to decrease by that time in gestation

Does oligohydramnios pose risks to mother or baby?

• The problems associated with oligohydramnios differ depending on the stage of the pregnancy.

• Oligohydramnios is more likely to have serious consequences if it occurs in the first half of pregnancy than if it occurs in the last trimester. These consequences include :

• Birth defects (too little amniotic fluid early in pregnancy can lead to compression of fetal organs, resulting in lung and limb defects)

• Miscarriage • Premature birth • Stillbirth

• When oligohydramnios occurs in the second half of pregnancy, it may be associated with poor fetal growth. Near term, oligohydramnios may increase the risk of complications of labor and delivery, including compression of the umbilical cord. This can deprive the baby of oxygen, sometimes resulting in stillbirth. Women with oligohydramnios are more likely than unaffected women to need a cesarean section.

What causes too little amniotic fluid?

• Premature rupture of the membranes • Birth defects, especially those involving the kidneys and urinary

tract. Babies with these birth defects produce less urine, which makes up most of the amniotic fluid.

• Post-term pregnancy (a pregnancy that lasts two or more weeks past the due date). Levels of amniotic fluid tend to decrease after the baby reaches full term.

• Maternal health conditions, including pregestational diabetes mellitus, high blood pressure and systemic lupus erythematosus (SLE).

• Certain medications. A group of medications used to treat high blood pressure, called angiotensin-converting enzyme inhibitors (like captopril), can damage the fetal kidneys and cause severe oligohydramnios and fetal death.

polyhydramnios

• About 1 percent of pregnant women have too much amniotic fluid .

• Most cases are minor and result from a gradual build up of excess fluid in the second half of pregnancy.

• However, a small number of women have a rapid build up of fluid occurring as early as 16 weeks of pregnancy that usually results in very early delivery

What complications can polyhydramnios cause for mother and baby?

• Polyhydramnios may increase the risk of pregnancy complications including :

• Premature delivery • Placental abruption (the placenta partially or

completely peels away from the uterine wall before delivery)

• Stillbirth • Postpartum hemorrhage (severe bleeding after

delivery) • Fetal malposition (the baby is not lying in a head-down

position and may need to be delivered by cesarean section)

What causes polyhydramnios?

• The most common birth defects that cause polyhydramnios are those that hinder fetal swallowing, such as birth defects involving the gastrointestinal tract and central nervous system.

• Normally, swallowing by the fetus, balanced by the production of fluid, maintains the fluid at a steady level.

• Other less common causes of polyhydramnios include :• Maternal-fetal blood incompatibilities (such as Rh

disease) • Twin-twin transfusion syndrome (TTTS); which one

fetus gets too much blood flow and the other too little because of connections between blood vessels in their shared placenta)

• Maternal diabetes • Fetal infection, such as with parvovirus B19 (which in

childhood commonly causes a mild illness called fifth disease)

Amniocentesis

• Amniocentesis is used to determine the health of an unborn baby.

• Amniotic fluid contains cells that are normally shed from the fetus. Samples of these cells are obtained by withdrawing some amniotic fluid.

• The chromosome analysis of these cells can be performed to determine abnormalities.

• In addition, the cells may be cultured and analyzed for enzymes, or for other materials that may indicate genetically transmitted diseases.

• Other studies can be done directly on the amniotic fluid including measurement of alpha-fetoprotein

Who is indicated amniocentesis? - That the pregnancy is 35 years or more. - Be suspicious of possible problems due to selective tests conducted previously - Family history of genetic alterations (in this case would be advisable to seek genetic counseling before becoming pregnant)

When we will have an amniocentesis? Usually made between 15 to 18 weeks, reaching even to 11 or 12. You should not worry you to extract a small amount of amniotic fluid for the fetus as quickly replaces. What are the risks of amniocentesis?

Like any invasive procedure there are risks, which are: - Abortion: about 1 in 200 to 400 women aborted (higher risk if done in the first quarter) - Uterine infection: 1 in 1000

How is an amniocentesis performed?

First we make an ECO to accurately pinpoint the location of the fetus, placenta, and therefore the best place for testing.

The doctor, after local anesthesia, inserts a needle using the ECO and will have the liquid sample.

After this, there will be an ECO again to make sure the normality of the baby's heartbeat.

When will the results be obtained?

In two weeks. This is important for the decision to be taken depending on the outcome. For levels of alpha fetoprotein (AFP) is not necessary to wait that long, so if they are too high, would suspect neural tube defect, and otherwise, Down syndrome if the level is too low.

Amniocentesis detects or rules out Down's syndrome, which causes mental retardation, congenital heart defects, and physical characteristics such as skin folds near the eyes. Amniocentesis also detects neural tube defects such as spina bifida. Babies born with spina bifida have a backbone that did not close properly. Serious complications of spina bifida can include leg paralysis, bladder and kidney defects, brain swelling (hydrocephalus), and mental retardation. If your pregnancy is complicated by a condition such as Rh-incombatibility, your doctor can use amniocentesis to find out if your baby's lungs are developed enough to endure an early delivery.