Common Prenatal Testing in the 2nd and 3rd Trimester

Group B Step

  • How –Your provider will swab your vaginal and rectal areas and send the swab for testing.
  • When - During the 35th – 37th week of pregnancy and results are usually available within 24-48 hours.
  • Why – Group Beta Strep is a type of bacteria that can be found in your rectum or vagina.
  • This normal bacterium is found in about 25% of all adult women. During birth it is possible for a mother to pass GBS to her baby during delivery.
  • About 1000 babies a year get early onset GBS disease each year in the United States.
  • Babies who acquire the GBS infection during birth are at increased risk for pneumonia, meningitis, sepsis (infection in the blood), breathing problems and organ problems.
  • Mothers who test positive for GBS during pregnancy will be treated with IV antibiotics during labor to minimize the risk of transmission to the baby during birth.

What if you test positive?

  • You will need to receive two rounds of antibiotics.
  • The standard is two doses 4 hours apart, each dose takes about 40 mins to administer. So you will need to plan to arrive at the hospital a minimum of 10 hours before you think you may deliver.
  • If you haven't delivered in that 4 hour window after the initial period, you may be given another dose every four hours until you deliver.
  • If you are allergic to penicillin, you will be given an alternative antibiotic.

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What if you are positive but refuse antibiotics or are unable to receive the initial 2 doses?

  • You may need to stay the full 48 hours in the hospital so baby can be monitored.

Non -Stress Test (NST)

  • How – A belt with a fetal heart rate monitor and a belt with a contraction monitor are attached to the mother’s abdomen. Fetal movement as well as how the baby’s heart rate reacts to movement are measured for 20-30 minutes.
  • When – For some women non-stress tests can begin as early as 28 weeks gestation. Non-stress testing is also common in pregnancies that are considered post dates.
  • Why – Non-stress testing is performed most commonly when a woman is considered high risk, expecting multiples, has high blood pressure or diabetes or if there is concern that the placenta is not functioning properly, or if you are past your due date.
  • A non-reassuring NST (non-stress test) may lead to further testing.

Biophysical Profile aka Ultrasound

  • How – The first step of a biophysical profile is a non-stress test we just talked about.
  • Once the non-stress test is complete the provider will use ultrasound to assess: fetal heart rate, breathing, movement, muscle tone and amniotic fluid level.
  • Each aspect is scored on a scale of 0-2 and a score of 8-10 is considered reassuring.
  • When – A biophysical profile is typically performed after 32 weeks of pregnancy although is sometimes used as early as 24 weeks.
  • Why – Used to evaluate and monitor your baby’s health, the goal of this test is to prevent loss and to detect adequate oxygenation of the baby. Other conditions that may prompt a provider to recommend a biophysical profile are:
  • Multiple pregnancy
  • Underlying conditions of the mother such as heart disease or diabetes
  • Pregnancy that has extended beyond the due date
  • Advanced maternal age
  • Decreased fetal movement
  • Preterm premature rupture of the membranes
  • Too much or too little amniotic fluid

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