--- title: "Third Trimester Prenatal Tests | Sutter Health" description: "Here is a brief description of the more common prenatal tests." url: "https://www.sutterhealth.org/health/third-trimester-prenatal-tests" --- 1. [Home](https://www.sutterhealth.org/) / 2. [Health and wellness](https://www.sutterhealth.org/health) / 3. Third Trimester Prenatal Tests # Third Trimester Prenatal Tests Your care team may order new lab tests during weeks 28-40 of your pregnancy. * * * August 18, 2025Medically reviewed by [Mary Abusief, M.D., FACOG](https://www.sutterhealth.org/find-provider/dr-mary-abusief-1046239946) As you enter the third trimester, your care team may recommend additional [tests](https://www.sutterhealth.org/services/prenatal-care-and-testing) based on your health history, age and other risk factors. These tests help your OB ensure you and your baby are healthy and ready for delivery. Your provider — and sometimes a genetic counselor — will review which tests are right for you and answer any questions you have. ![third-trimester-prenatal-tests-1664a](https://edge.sitecorecloud.io/sutterhealt962c-sutterhealt8fce-production57cc-4860/media/Project/SutterHealth/SutterHealth/Images/health-topics/birth-babies/third-trimester-prenatal-tests-1664a.jpg) ## Common Prenatal Tests in the Third Trimester  **Biophysical Profile (BPP)**  A combination of ultrasound and fetal monitoring that checks your baby’s heartbeat, movements, breathing pattern, placenta and the amount of amniotic fluid. Think of it as a thorough “in utero” checkup.   **Contraction Stress Test (CST)**  Assesses how your baby handles the stress of contractions. Uterus contractions are brought on by gently stimulating your nipples, and your baby’s heart rate is monitored. **Nonstress Test (NST)**  Checks your baby’s well-being by monitoring their heart rate during movement using an electronic fetal monitor.  **Oxytocin Challenge Test (OCT)**  Similar to the CST, but contractions are started with a small dose of oxytocin (pitocin) through an IV. This is usually done if nipple stimulation doesn’t bring on strong enough contractions.  **Group B Streptococcus (GBS)**  GBS is a common bacteria that can be passed to your baby during birth. Around 35–37 weeks, your provider will take a quick swab of your vagina and rectum to test for it. If GBS is present, you’ll receive antibiotics during labor to protect your baby from infection.  ## Explore related topics [Pregnancy](https://www.sutterhealth.org/health/articles?facets=%5B%7B%22i%22%3A%22c_healthTopics.name%22%2C%22v%22%3A%5B%22Pregnancy%22%5D%7D%2C%7B%22i%22%3A%22builtin.entityType%22%2C%22v%22%3A%5B%22Sutter+Health+Page%22%5D%7D%5D&limit=10&verticalKey=health-and-wellness)[Prenatal Tests](https://www.sutterhealth.org/health/articles?facets=%5B%7B%22i%22%3A%22c_healthTopics.name%22%2C%22v%22%3A%5B%22Prenatal+Tests%22%5D%7D%2C%7B%22i%22%3A%22builtin.entityType%22%2C%22v%22%3A%5B%22Sutter+Health+Page%22%5D%7D%5D&limit=10&verticalKey=health-and-wellness)[Third Trimester](https://www.sutterhealth.org/health/articles?facets=%5B%7B%22i%22%3A%22c_healthTopics.name%22%2C%22v%22%3A%5B%22Third+Trimester%22%5D%7D%2C%7B%22i%22%3A%22builtin.entityType%22%2C%22v%22%3A%5B%22Sutter+Health+Page%22%5D%7D%5D&limit=10&verticalKey=health-and-wellness) ##  Support at Every Step From conception to delivery and after, our [pregnancy and childbirth](https://www.sutterhealth.org/services/pregnancy-and-childbirth) providers put you first. [Schedule an Appointment](https://www.sutterhealth.org/find-provider-results?facets=%5B%7B%22i%22%3A%22c_providerSpecialties.specialty.name%22%2C%22v%22%3A%5B%22Infertility%22%2C%22Nurse+Midwife%22%2C%22Obstetrics+and+Gynecology%22%2C%22Reproductive+Endocrinology%22%5D%7D%5D&limit=10&verticalKey=healthcare_professionals) ## Meet our care team ![Mary Abusief, M.D., FACOG](http://a.mktgcdn.com/p/vIpKN-F-qkaLJTty4pEsxDaDl0ukpkV08qGZTwBQD4U/480x480.jpg) [Mary Abusief, M.D., FACOG](https://www.sutterhealth.org/find-provider/dr-mary-abusief-1046239946) Reproductive Endocrinology and Infertility (REI) Obstetrics and Gynecology ```json {"@context":"https://schema.org","@type":"MedicalOrganization","name":"Sutter Health","@id":"https://www.sutterhealth.org/#medicalorganization","url":"https://www.sutterhealth.org","logo":"https://www.sutterhealth.org/static/images/sutter-health-logo.svg","address":{"@type":"PostalAddress","streetAddress":"2200 River Plaza Drive","addressLocality":"Sacramento","addressRegion":"CA","postalCode":"95833","addressCountry":"US"},"areaServed":{"@type":"AdministrativeArea","name":"California"},"sameAs":["https://www.facebook.com/SutterHealth","https://www.instagram.com/sutterhealth/","https://x.com/SutterHealth","https://www.youtube.com/sutterhealth","https://www.linkedin.com/company/sutter-health","https://en.wikipedia.org/wiki/Sutter_Health"]} ``` ```json {"@context":"https://schema.org","@type":"WebPage","name":"Third Trimester Prenatal Tests | Sutter Health","description":"Here is a brief description of the more common prenatal tests.","url":"https://www.sutterhealth.org/health/third-trimester-prenatal-tests","breadcrumb":{"@id":"https://www.sutterhealth.org/health/third-trimester-prenatal-tests#breadcrumblist"}} ``` ```json {"@context":"https://schema.org","headline":"Third Trimester Prenatal Tests","alternativeHeadline":"Third Trimester Prenatal Tests | Sutter Health","description":"Here is a brief description of the more common prenatal tests.","datePublished":"2025-08-18T00:00:00Z","dateModified":"2026-10-23T16:03:49Z","publisher":{"@type":"MedicalOrganization","name":"Sutter Health","@id":"https://www.sutterhealth.org/#medicalorganization","url":"https://www.sutterhealth.org"},"image":{"@type":"ImageObject","url":"https://edge.sitecorecloud.io/sutterhealt962c-sutterhealt8fce-production57cc-4860/media/Project/SutterHealth/SutterHealth/Images/health-topics/birth-babies/third-trimester-prenatal-tests-1664a.jpg?h=878&iar=0&w=1664","width":"1664","height":"878","caption":"third-trimester-prenatal-tests-1664a"},"@type":"MedicalWebPage","breadcrumb":{"@id":"https://www.sutterhealth.org/health/third-trimester-prenatal-tests#breadcrumblist"},"reviewedBy":[{"@context":"https://schema.org","@type":"Person","name":"Mary Abusief, M.D., FACOG","url":"https://www.sutterhealth.org/find-provider/dr-mary-abusief-1046239946"}],"lastReviewed":"2026-10-23T16:03:49Z"} ``` ```json {"@context":"https://schema.org","@type":"BreadcrumbList","@id":"https://www.sutterhealth.org/health/third-trimester-prenatal-tests#breadcrumblist","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://www.sutterhealth.org/"},{"@type":"ListItem","position":2,"name":"Health and wellness","item":"https://www.sutterhealth.org/health"},{"@type":"ListItem","position":3,"name":"Third Trimester Prenatal Tests"}]} ```