Amniocentesis – the why and how

During your pregnancy, you will be asked to take a series of test. One of them is amniocentesis.

This prenatal test, allows your doctor/ gynecologist to assess your baby’s health, based on the findings of a sample of your amniotic fluid (which cushions your little one inside the uterus). Under local anesthesia, a needle is usually first inserted through the mother’s abdominal wall, then through the uterine wall, and finally pierces the amniotic sac to get a sample.


At which stage of your pregnancy is amniocentesis done?

Well, this test is usually done in the first trimester and is carried out between 16 and 20 weeks of your pregnancy.

Why is it indicated?

An “amnio” is generally advised to women whose baby carries an increased risk for:

  • Genetic and/or chromosomal problems like Down syndrome, cystic fibrosis, sickle cell disease, trisomy 13, Tay-Sachs disease, trisomy 18, and sex chromosome abnormalities (such as Turner syndrome).The diagnosis of such conditions can be done, but the extent of their severity cannot be measured.
  • Neural tube defects like spina bifida and anencephaly (in the amniotic fluid the levels of alpha-fetoprotein (AFP) is measured)


How does it work?

Well, amniocentesis produces a karyotype – a picture of your baby’s chromosomes (like chorionic villus sampling (CVS), another prenatal test done in the first trimester). This gives the doctor a clear picture if there is an issue to worry about.


Other reasons for an amniocentesis include:

  • To evaluate the development of your baby’s lungs in case of an early delivery (unless it is proved otherwise).
  • To check if you and your baby have Rh sensitization,
  • To rule out/diagnose an intrauterine infection


Complications of amniocentesis

Since this is an invasive procedure, there lies a slight risk of miscarriage (when performed in the hands of a competent practitioner, there is barely any reason to be worried).




Dr. Aishwarya Rajeev has completed her MDS degree and is currently pursuing her PhD. She is an avid reader and loves to teach and write!

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