Amniocentesis Periprocedural Care

Patient Instructions

Patients need to be aware of the description of the procedure and the risks, including but not limited to fetal and or maternal infection, fetal damage, preterm labor, puncture of maternal organs, separation of the placenta, and possible miscarriage, which occurs between 1 case in 200 and 1 case in 1000 for genetic amniocentesis.

Additionally, genetic amniocentesis can detect all chromosomal anomalies and some but not all genetic diseases. Therefore, the patient needs to understand the limitations of this procedure and testing.

The patient does not need to be in a fasting state, although it may be recommended if the amniocentesis is performed at a gestational age when the fetus is viable, in the event that a rapid intervention such as a cesarean needs to be performed.

Amniocentesis is usually performed at the physician’s office ultrasound room or in the labor and delivery unit of a hospital equipped to manage complications. The mother’s blood type and group, number of fetuses, and a gross evaluation for anatomical anomalies should be performed beforehand. Fetal heart tones, placental position, and distribution of the amniotic fluid should be evaluated right before the procedure.

Real-time ultrasound with a transducer of 3.5 MHZ is usually used during obstetrical ultrasounds. A skin disinfectant (such as Betadine), a spinal needle (20-22 gauge), and sterile syringes to collect amniotic fluid are also needed. An 18-gauge spinal needle can be used if lots of amniotic fluid is being removed; a therapeutic amniocentesis done to treat polyhydramnios may involve removing 2-3 liters of fluid. Collection tubes should be readily available depending on the test(s) requested.

Anesthesia

Anesthesia is usually not necessarily during amniocentesis because the needle used has a small diameter; although, in some situations, a patient may benefit from the use of anesthesia or anxiolytics. Some discomfort may be experienced by the patient with the initial insertion of the needle into the skin.

Positioning

The patient usually lies in a dorsal lithotomy position to expose the skin of the abdomen to the operator. Sometimes the patient is asked to rotate her body to her left or right side, depending on the position of the placenta, fetus, and the distribution of amniotic fluid in the uterine cavity.

After the procedure is completed, the presence of fetal heart tones by ultrasound should be obtained and documented; also document bleeding through the needle insertion site, abdominal pain, or contractions. If the patient is Rh negative and nonsensitized, she will require 300 micrograms of Rhogam to prevent the generation of anti-D antibodies.

The most common complication after an amniocentesis is cramping; it usually lasts for less than 2 hours. Chorioamnionitis is rare but may have a fatal fetal outcome. Vaginal bleeding or leakage of fluid occurs in about 2% of cases, and most of the time this is self-limited.

Miscarriage after amniocentesis has been traditionally reported as 1 in 200, but most recent studies report the risk to be 1 in 1,000. Amniocentesis before 15 weeks gestation, use of large needles, multiple attempts, and unrecognized chorioamnionitis postprocedure are risk factors for miscarriage. The risk of talipes equinovarus is elevated if the amniocentesis is performed prior to 15 weeks gestation. ^{[5, 7]}