Why You May Need a 3rd Trimester Amniocentesis

Most surrogates are at least familiar enough with an amniocentesis procedure to know that it’s typically done in the early second trimester, if needed. This test is typically completed as part of a diagnostic screening to evaluate the risk that a fetus may have chromosomal abnormalities such as Down syndrome. Knowing this, it can be jarring to hear that a care provider may want you to have one in your third trimester. Administered in the last 12 weeks of pregnancy, the test takes on a different purpose. Here’s a look at what it means to need this invasive test in the weeks leading up to delivery.

The procedure itself is identical no matter which trimester it is performed in. A doctor will use an abdominal ultrasound to guide a long needle into your uterus to extract some amniotic fluid. All care will be taken to not touch the baby with the needle. The entire process takes about 45 minutes and is generally not incredibly uncomfortable for the surrogate.

However, when completed in late pregnancy, the goal of an amniocentesis is not to evaluate the risk of chromosomal abnormalities. Instead, your care provider is likely looking for one of 3 potential conditions. These include:

  1. Detection of uterine infection after a premature rupture of the membranes (if your water broke too early, or you have a small tear causing amniotic fluid to leak.)
  2. Fetal anemia in the instance of a fetus with Rh disease. In some cases, fetal anemia is a life-threatening condition that requires a fetal blood transfusion.
  3. To evaluate lung maturity preceding a premature delivery.

The follow-up and recovery of a late amniocentesis is similar to that of one performed in the second trimester. You may experience some leaking, discomfort at the needle injection site, and general tenderness. Some mild cramping or uterine contractions can also be expected.

Most women will not need for a late-term amniocentesis. If a doctor suggests a third-trimester amnio, you will need to consult with your case specialist and intended parents right away. In most cases, it is not advisable to decline the test at this stage.

Kim Bergman, PhD, a licensed psychologist of 26 years, has specialized in the area of gay and lesbian parenting, parenting by choice and third party assisted reproduction for over two decades. Dr. Bergman has created a comprehensive psychological screening, support and monitoring process for intended parents, surrogates and donors. She is the co-owner of Growing Generations and is a member of the American Society for Reproductive Medicine, the American Psychological Association, the Los Angeles County Psychological Association, the Lesbian and Gay Psychotherapy Association, and the Gay and Lesbian Medical Association. She is on the national Emeritus board of the Family Equality Council. Dr. Bergman writes, teaches and speaks extensively on parenting by choice. Along with co-authors, she published “Gay Men Who Become Fathers via Surrogacy: The Transition to Parenthood” (Journal of GLBT Family Studies, April 2010). Dr. Bergman’s is the author of the book, Your Future Family: The Essential Guide to Assisted Reproduction (Conari Press 2019) as well as the children's book You Began as a Wish (Independent Press 2019). Dr. Bergman created her own family using third party assisted reproduction and she lives with her wife of 35 years. She has two adult daughters.