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What Are the Tests Performed by Weeks of Pregnancy?

Tests performed during pregnancy follow-up are very important for evaluating the baby’s development, detecting possible risks early, and planning a healthy pregnancy process. These tests are carried out for different purposes in each trimester:

Weeks 0–13: First Trimester Tests

The first trimester is a critical period when the baby’s basic organ development begins and the healthy progression of the pregnancy is evaluated. The main tests performed during this period include:

• Non-Invasive Prenatal Test (NIPT): An advanced screening test used to assess the risk of certain chromosomal abnormalities in the baby. It is generally performed from the 10th week of pregnancy onward.
• Double screening test (Weeks 12–13): Used to calculate the risk of certain chromosomal abnormalities such as Down syndrome. It is evaluated together with nuchal translucency measurement.

Weeks 14–27: Second Trimester Tests

The second trimester is the period when the baby’s anatomical development is examined in detail and some structural risks are assessed. The main tests performed during this period include:

• Triple or quadruple screening test: Risk assessment is performed for chromosomal abnormalities such as Down syndrome and Edwards syndrome, as well as neural tube defects.
• Detailed ultrasound (anomaly scan) (Weeks 18–23): The development of the baby’s brain, heart, spine, and internal organs is examined in detail.
• Glucose screening test (Weeks 24–26): Screening is performed for gestational diabetes.

Weeks 28–40: Third Trimester Tests

The final trimester covers the preparation period for childbirth. Tests performed during this period aim to evaluate the baby’s well-being in the womb and readiness for delivery. The main tests include:

• NST (Non-Stress Test): The baby’s heart rate and movements are monitored to assess well-being in the womb.
• Ultrasound: The baby’s estimated birth weight, amniotic fluid volume, and the condition of the placenta are evaluated.
• Blood tests: Assessments are made for anemia, infections, and conditions that may prevent delivery.
• Urinary tract infection screening: Urine tests are used to monitor the presence of infection.
• Weight and blood pressure monitoring: The mother’s weight gain and blood pressure are regularly monitored. These follow-ups help detect conditions such as preeclampsia at an early stage.
• Blood incompatibility injection (Anti-D Immunoglobulin): In Rh-negative mothers, it is generally administered around the 28th week when necessary to prevent immune response against the baby’s blood cells.

Frequently Asked Questions About Pregnancy Calculation

Why Is Pregnancy Calculated Based on the Last Menstrual Period?

Because the exact date of fertilization is often unknown, while the last menstrual period is easy to remember and provides a standardized starting point.

How Many Days Before a Period Is Pregnancy Unlikely?

Generally, the chance of becoming pregnant 3–4 days before a period is very low, but not completely impossible.

How Many Days After a Period Can Pregnancy Occur?

On average, the likelihood of pregnancy is highest during the ovulation period, about 10–14 days after the start of the menstrual period.

Why Is Pregnancy Calculated as 40 Weeks?

Pregnancy duration is accepted as approximately 280 days (40 weeks) from the first day of the last menstrual period, which is a medical standard.

What Happens If Labor Does Not Start at 40 Weeks?

The mother and baby are closely monitored under medical supervision, and labor may be induced if necessary.

At the Latest, Which Week Does Delivery Occur?

Pregnancy can generally be monitored until the 41st week; pregnancies approaching the 42nd week are medically evaluated in detail.