The first ultrasound in pregnancy — and how many follow
The test is positive, and the next question is when to book. Too early and there is nothing to see; too late and you can miss windows that are tied to specific weeks. Here is the whole schedule in order: what happens before week ten, what happens at 11–13, what comes after, and why those windows cannot be moved.
When the first scan is worth doing
Before week six, counted from the first day of your last period, there is little point in booking: the gestational sac is still too small, and all you are likely to hear is “come back in a week”. A sensible time for the first scan is weeks 6 to 9.
At that point the scan answers four questions, and all four matter right now:
- is the pregnancy in the uterus — rather than ectopic;
- how many embryos — and if there are two, whether they share one placenta: this decides how the whole pregnancy will be managed, and it can only be established in the first trimester;
- is there a heartbeat — it appears at around six weeks;
- how far along you are — from the crown-rump length of the embryo. Up to 14 weeks this is the most reliable way to date a pregnancy, and every later scan is counted from that date.
The last point is why waiting is a bad idea. Dating by the last period is off by a week or more in any woman with an irregular cycle or late ovulation. If the dates are wrong, the first trimester screening window can simply be missed.
The schedule for the whole pregnancy
In Poland the timings are tied to weeks strictly: each scan answers a question that is only visible inside its own window. A missed window does not roll over — what would be assessed at twelve weeks is no longer visible at sixteen.
| Timing | What it is | What is assessed |
|---|---|---|
| up to week 10 | early scan | pregnancy inside the uterus, number of embryos, heartbeat, dating from crown-rump length |
| 11+0 – 13+6 weeks | first trimester screening | nuchal translucency, nasal bone, blood flow; together with a blood test (PAPP-A and free β-hCG) it gives the risk of chromosomal abnormalities |
| 18 – 22 weeks | anatomy scan | detailed review of the baby’s organs: heart, brain, spine, kidneys, placenta, and the length of the cervix |
| 28 – 32 weeks | third trimester scan | growth, blood flow in the cord and uterine vessels, position and maturity of the placenta, amount of fluid |
| after week 36 | before delivery | presentation, estimated weight, fluid, wellbeing of the baby |
Three scans — at 11–14, 18–22 and 27–32 weeks — are part of the Polish standard of perinatal care and are covered by the NFZ. The early scan before week ten and the scan before delivery are recommended in addition; in private practice they are usually done for everyone.
Why the 11+0 – 13+6 window cannot move
This is the only scan in the whole pregnancy whose limits are given to the day. The reason is what is being measured: nuchal translucency, a thin layer of fluid under the skin at the back of the baby’s neck. Before eleven weeks it is too small to measure; after fourteen it is absorbed. There is nothing to measure either side of the window.
The risk calculation has three parts: your age, the measurements from the scan, and two proteins from your blood — PAPP-A and free β-hCG. The blood is taken in the same period, usually at 11 to 12 weeks. The result is not a diagnosis but a probability: “1 in 5000” means low risk, “1 in 100” is a reason to discuss a definitive test, most often NIPT from the mother’s blood or an amniocentesis.
If the dates come from your last period and are a week out, you arrive “at twelve weeks” and the scan says ten — and you have to come back. That is the most practical argument for an early scan.
The scan at 18 to 22 weeks
The most detailed scan of the pregnancy and the longest — up to forty minutes. The baby is fully formed but still small enough to fit in the field of view whole, and mobile enough to be seen from every side. The examination follows a list: the four chambers of the heart and the great vessels, the structures of the brain, the face and profile, the spine, the abdominal wall, the stomach, the kidneys and bladder, the bones of the limbs.
The length of the cervix is measured at the same visit — a short cervix at this stage is the strongest predictor of preterm birth, and it is the one thing that can still be acted on.
If the baby is lying awkwardly and some organs could not be seen, a repeat is booked in one or two weeks. That is routine, not a sign that something was found.
Safety and how often
Ultrasound uses no ionising radiation, and decades of use have not shown harm to the baby. The principle followed is “as low as reasonably achievable”: scans are done for a reason, not to check in on how the baby is doing.
A separate word on keepsake 3D and 4D scans in shopping centres: these are not medical examinations, nobody reports them and nobody is responsible for what they miss. Three-dimensional imaging is genuinely useful in a clinical scan — for the face or the spine, for instance — but as part of the examination, not instead of it.
A private scan needs no referral and no NFZ insurance. Bring previous reports with you: comparison matters more than a single measurement, and growth is assessed precisely by how it changes.
Short answers
When should the first ultrasound in pregnancy be done?
Weeks 6 to 9 from the first day of your last period. Before week six there is usually nothing to see. At that stage the scan confirms the pregnancy is inside the uterus, counts the embryos, looks for the heartbeat and dates the pregnancy from the size of the embryo.
How many scans are done during pregnancy?
The Polish standard of care includes three — at 11–14, 18–22 and 27–32 weeks. An early scan before week ten and a scan after week 36 are usually added, giving four or five in an uncomplicated pregnancy.
Why is first trimester screening done strictly between 11 and 13+6 weeks?
Because it measures nuchal translucency, a layer of fluid under the skin of the baby’s neck. Before eleven weeks it is too small to measure; after fourteen it is absorbed. Outside that window the scan loses its meaning.
Is frequent ultrasound in pregnancy harmful?
Ultrasound uses no radiation and has not been shown to harm the baby. Even so, scans are done for a clinical reason rather than to look at the baby: it is a medical procedure, not a photo session.
Do I need a referral for a pregnancy scan?
Not for a private appointment, and no NFZ insurance either. Just book. Bring any previous reports if you have them.
This text describes the general picture and does not replace a consultation. Timings and indications differ from woman to woman and are decided at the appointment, from your history and test results.
