Prenatal care
Prenatal tests by trimester: what your provider may offer and when
May 26, 2026 · 7 min read
Pregnancy comes with a schedule of tests, and it can feel like alphabet soup: NIPT, AFP, GBS. This guide walks through the screenings your provider may offer in each trimester, what each one looks for, and roughly when it happens. It is education, not a prescription. Your own plan is set with your provider, based on your history and your preferences.
First trimester: confirming and dating the pregnancy
Early visits usually focus on the basics. Your provider may confirm the pregnancy, estimate your due date, and often offer an early ultrasound to check how far along you are. Accurate dating matters because almost every later test is timed against it. You will also typically be asked about your health history, medications, and any prior pregnancies, which helps your provider decide which screenings make sense for you.
First trimester: the initial lab panel
Most providers order a set of routine labs early on. These commonly include your blood type and Rh factor, a blood count to check for anemia, screening for infections such as hepatitis B, syphilis, and HIV, a check of immunity to rubella, and a urine test. None of these are exotic. They establish a baseline so that anything that changes later stands out, and they catch treatable conditions early.
First trimester: genetic screening options
Genetic screening is optional, and your provider may walk you through the choices. Cell-free DNA screening, often called NIPT, is a blood test available from about 10 weeks that screens for certain chromosomal conditions (ACOG). There are also combined first trimester screens that pair a blood test with an ultrasound measurement, and carrier screening that looks at your own genes. Screening tests estimate risk. They do not diagnose, and a screening result is usually followed by a conversation, not a conclusion.
Second trimester: the anatomy scan
The detailed anatomy ultrasound is typically offered between about 18 and 22 weeks (ACOG). It is the long, thorough scan where the sonographer examines the baby from head to toe: heart, brain, spine, limbs, and the placenta. For many families it is also the appointment where they learn the baby's sex, if they want to know. If something needs a closer look, your provider may suggest a follow-up scan or a referral, which is a common and often reassuring next step.
Second trimester: the glucose screen
Screening for gestational diabetes is usually offered between 24 and 28 weeks (ACOG). The common version is a sugary drink followed by a blood draw about an hour later. If that screen comes back high, a longer confirmatory test usually follows. Gestational diabetes is manageable, and finding it matters because treating it protects both you and the baby. Some providers screen earlier if your history suggests higher risk.
Third trimester: GBS and closer monitoring
Between 36 and 37 weeks, providers typically offer a swab test for group B streptococcus, a common bacteria that is harmless to adults but can affect newborns during delivery; a positive result usually means antibiotics during labor (ACOG). Third trimester visits also get more frequent, with regular blood pressure checks, urine checks, and attention to the baby's movement and position. If you ever notice reduced movement, severe headache, vision changes, or heavy bleeding, contact your provider right away, and for an emergency call 911.
Frequently asked questions
- Do I have to take every test on this list?
- No. Some tests are routinely recommended and others, like genetic screening, are optional. Your provider should explain what each test is for so you can decide together. This article is education only and does not replace that conversation.
- What is the difference between a screening test and a diagnostic test?
- A screening test estimates the chance that a condition is present, while a diagnostic test confirms or rules it out. A positive screen does not mean something is wrong. It means your provider may offer more information or further testing.
- How can the Mommy Passport help with my test schedule?
- The Mommy Passport keeps your visits, labs, and screening results in one patient-owned record on your phone, in English or Spanish, so every provider you see starts with your full history. It is free for patients, always.