← All decks
Radiology
Amniocentesis
Built from Obstetric Imaging
What’s inside
8 sections · 63 slides
Overview
- Scope of this deck
Definition and timing
A needle through the abdomen into the fluid around the fetus
- Definition of amniocentesis
- Amniocentesis under ultrasound guidance
- Needle entering the amniotic fluid pocket
- Timing of the procedure
- 15 wk
- Risks of amniocentesis before 15 weeks
- Talipes equinovarus in a newborn
Preparation
Who performs it, what is said beforehand, and what the scan must show
- Operator requirements
- Content of the consent discussion
- Equipment for amniocentesis
- Ultrasound transducer held on the abdomen
- Ultrasound assessment before every amniocentesis
- Second-trimester fetus on ultrasound
- Amnion-chorion separation
- Sequence before needle insertion
Technique
From skin preparation to the last check of the fetal heart
- Skin preparation and needle entry
- Freehand technique versus a needle guide
- Volume taken and sample handling
- Syringes of aspirated amniotic fluid
- Needle withdrawal, checks and attempt limits
- Transplacental needle passage
- Order of steps at the bedside
Twins and higher multiples
Every sac sampled, and every sample traced to the right fetus
- Mapping fetuses in a multifetal pregnancy
- Indigo carmine dye technique
- Methylene blue and fetal bowel atresia
- Single-puncture instillation-free technique
- Iatrogenic monoamniotic sac
- Sampling triplets and higher-order multiples
- Techniques for separating twin samples
Indications
What the withdrawn fluid is actually tested for
- Common indications for amniocentesis
- Further indications
- Genetic tests performed on amniotic fluid
- Cultured versus uncultured amniotic fluid cells
- Copy number variants on chromosomal microarray
- ACOG and SMFM recommendation on first-line testing
- Added yield of prenatal exome sequencing
- Exome sequencing yield by organ system
- Limitations of fetal exome sequencing
- Ladder of genetic testing on amniotic fluid
- Karyogram from an amniocentesis sample
- Fetal lung maturity testing
- Amniotic fluid tests of fetal lung maturity
Complications
From ordinary cramping to the rare injuries of a needle strike
- Expected symptoms after the procedure
- Amniotic fluid leakage and vaginal bleeding
- Intraamniotic infection after amniocentesis
- Rhesus isoimmunisation and anti-D prophylaxis
- Inadvertent fetal puncture
- Injuries reported after direct fetal puncture
Pregnancy loss
The figure that dominates counselling, and how far it has fallen
- Procedure-related pregnancy loss rate
- 0.11%
- Comparison with unsampled controls
- Fetal loss in twin pregnancies with and without amniocentesis
- Clinical factors that raise pregnancy loss risk
- Increased risks at 13 to 14 weeks' gestation
- Counselling in twin pregnancies
- Key points
- Overview of amniocentesis
- References
- References (continued)
- References (continued)
- References (continued)
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition