Amniocentesis is an invasive prenatal diagnostic technique by which a small amount of amniotic fluid is extracted from the gestational sac, with which it is possible to perform certain studies.
It is performed through the mother’s abdomen, without the need for anesthesia, using a fine needle and under ultrasound control (in this way the fetus is always visualized and puncture is avoided). The surface of the maternal skin has been previously disinfected to prevent germs from being carried along. The amniotic sac is punctured, away from the fetus, and once the needle is located, the amniotic fluid is aspirated with a syringe. The extracted fluid is regenerated within a few hours.
Rest and care after amniocentesis
No special preparation is necessary for amniocentesis. It is performed on an outpatient basis from 14 weeks of gestation and the patient can return home immediately without any problems. She is warned that in the next few hours she may have pelvic discomfort that is not important.
In our center, the recommendations to the pregnant woman after an amniocentesis are:
– Home rest for 24 hours (bed rest is not necessary, but she should remain as long as possible at rest, e.g. on the couch, although she can get up to eat, go to the bathroom or climb a few stairs).
– After this, we recommend 3-4 days of relative rest, i.e. your usual life with as much rest as possible, including no abdominal efforts, no long walks, avoiding sports and avoiding sexual relations. We also recommend avoiding immersion baths (bathtub or swimming pool), but this is certainly a recommendation that has no scientific basis.
The only alarming factor to go to the clinic is bleeding or vaginal fluid leakage.
If the woman is Rh negative, with an Rh positive father, anti-D gamma globulin is administered to the mother to avoid possible immunization in case the fetus is Rh positive (the latter situation is unknown to us).
Indications or situations which would make it advisable, or not, to perform the procedure
There are some indications that we will call “classic”, which are related to certain risk factors: a history of a child with a chromosomal anomaly, one of the parents being a carrier of a chromosomal anomaly, repeated miscarriages or a history of unexplained fetal death, any anatomical anomaly detected in the fetus that leads one to suspect that it may be a carrier of a chromosomal disease, and, the best known, advanced maternal age.
The older the maternal age, the higher the risk of chromosomal abnormalities, mainly trisomies, such as Down syndrome, because there are other chromosomal abnormalities that are not related to age.
However, there is currently an indication that has grown significantly: the desire of the parents, because of their concern (wrongly called anxiety) as to whether the fetus is healthy.
The number of pregnant women who “a priori” could undergo amniocentesis has increased in the last 20 years, mainly due to the increase in the age of the pregnant woman.
But there are also other reasons: fewer children, first child at a later age (currently the average is over 32 years of age), greater number of pregnancies obtained after reproductive techniques.
It is also true that new non-invasive prenatal diagnostic methods have emerged, in maternal blood, especially those related to Down syndrome (trisomy 21), which could reduce the number of amniocentesis, although at the cost of not detecting other anomalies.
It is difficult to find absolute contraindications for amniocentesis, although there are situations in which the risk/benefit ratio of its performance must be assessed: presence of uterine fibroids, mother carrying diseases that could be contagious to the fetus, etc.
Risks of amniocentesis
The main risk is that of miscarriage following the test. Classically there has been talk of a risk of one percent, which is clearly exaggerated nowadays, with higher resolution ultrasound scanners and more qualified personnel.
Experienced centers estimate a 0.1 to 0.3 percent risk of miscarriage associated with amniocentesis.