Amniocentesis During Pregnancy: What Every Expectant Mother Should Know
Learn what amniocentesis is, why it's done, and its risks, explained clearly by Dr. Najeeb Layyous.
In short: Amniocentesis is the taking of a small sample of the fluid around the baby to diagnose chromosome and genetic disorders such as Down syndrome. It is done between weeks 15 and 20 and is advised over the age of 35, after an abnormal screening result, or with a family history. The risk of miscarriage from the test is about 1 in 400–500.
Sometimes an ultrasound scan shows that a baby is not growing quite as expected, has a structural difference, or shows fluid collection behind the neck. Other times, hereditary or genetic conditions cause no visible signs at all on ultrasound and are only discovered after birth. Thankfully, the technique of examining the amniotic fluid — known as amniocentesis — allows doctors to diagnose many chromosomal and genetic problems in the fetus while it is still inside the mother’s womb, giving families clearer answers earlier in pregnancy.
Expectant mothers in this age group may also wish to read our article on pregnancy after 35.
With this information, doctors can plan the right next steps — whether that means treating the fetus, discussing options around the pregnancy, or preparing for postpartum care by arranging an NICU bed and pediatric support the baby might need.
The test can detect chromosomal abnormalities such as Down syndrome, and, when a specific family risk is known, genetic conditions such as cystic fibrosis, sickle cell anemia, thalassemia, Tay-Sachs disease or muscular dystrophy. Spina bifida is now mainly diagnosed by detailed ultrasound. Today, amniocentesis is usually offered when a screening test (such as the combined first-trimester test or cell-free DNA/NIPT) shows a high chance of a chromosomal condition, when the ultrasound shows an abnormality, or when the family has a known genetic condition. Age alone is no longer a reason for amniocentesis.
It is also possible to analyze amniotic fluid to check for possible infections inside the uterus, so that necessary antibiotic treatment can be given before a miscarriage or premature birth occurs.
In cases of rhesus disease, fetal anemia is now checked with a special Doppler ultrasound of the blood flow in the baby’s brain (MCA Doppler), without the need for amniocentesis, to decide whether a blood transfusion for the fetus inside the uterus is needed.
There are also cases of high amniotic fluid pressure inside the uterus that require withdrawal of some fluid to reduce the pressure — this can help ease the mother’s breathing and reduce the risk of premature birth.
Amniotic fluid examination is a diagnostic test performed during pregnancy to obtain a small sample of the fluid surrounding the fetus. It’s a relatively simple procedure that allows examination of the fetus’s genetic material (DNA), usually between 15–20 weeks of pregnancy, as follows:
- Under sterile conditions, the abdomen is cleaned, a numbing material is applied to minimize discomfort, and a fine needle is guided through the abdominal wall into the uterus under continuous ultrasound guidance. A small sample of the surrounding fluid (about 20 ml) is gently withdrawn. The entire procedure is performed under direct ultrasound visualization for safety. The sample, which contains fetal cells and fetal DNA, is then sent to the laboratory to be studied for chromosomal abnormalities, genetic conditions, or — in some cases — signs of infection inside the uterus.
Most mothers can return to their normal daily activities right after the examination.
A rapid result for the most common chromosomal conditions (such as Down syndrome) is usually available within 1–3 days; the full chromosome or genetic analysis takes about 1–3 weeks, depending on the laboratory technique used.
When might amniocentesis not be recommended?
1- If the mother has a viral infection (such as hepatitis B, hepatitis C or HIV), the procedure needs extra care: viral levels are checked first (and for HIV, treatment should ideally be started beforehand) to reduce the small risk of passing the infection to the baby.
2- If the mother has a bleeding disorder (bleeding diathesis) or is currently experiencing active bleeding.
3- If there are contractions in the uterus or signs of infection inside the uterus.
What are the possible complications?
Amniocentesis is an invasive procedure and, like any medical procedure, carries some risks for both mother and baby:
2- Placental abruption
3- Miscarriage (pregnancy loss) — the risk of miscarriage is estimated at about 1 in 400 to 500 procedures.
4- Infection inside the uterus
5- In Rh-negative mothers, the baby’s blood can cause the mother to form antibodies, so an anti-D injection is given after the procedure (and in existing rhesus disease, antibody levels may rise)
6- Positional issues affecting the fetus’s limbs, related to withdrawal of an excessive amount of fluid
A related topic, steroid injections for the baby’s lungs, is covered in a separate article.
Because of these risks, amniocentesis should only be performed by a specialist who is properly trained, experienced, and familiar with the technique and its possible complications. If you have questions about whether amniocentesis is right for your pregnancy,
Dr. Najeeb Layyous and his team are here to guide you through your options with care and clear explanations.
Dr Najeeb Layyous F.R.C.O.G
Consultant Obstetrician, Gynecologist and Infertility Specialist
The finest doctor in Jordan — may God bless him and his whole medical team. A doctor in every sense of the word. I advise anyone planning a pregnancy to visit Dr. Najeeb Layyous. His manner is wonderful, always smiling, with the highest ethics; he gives every patient her due, and the patient’s comfort matters most to him. We had been to many doctors and none understood and treated my case except him. Special thanks to him and the whole team, and to Dina in particular — a lovely person. I recommend anyone considering IVF or pregnancy to visit his clinic.