Understanding Your Pregnancy Scan Report
CRL, MSD, FHR, EDD — the abbreviations on an early pregnancy report, translated, along with what the numbers do and do not tell you.
Reports are written for clinicians, which means they are precise and often opaque. Everything meaningful in yours will have been explained to you at the appointment — this page is for the reading you do afterwards, at home, when a term you skimmed past starts to nag.
The abbreviations, decoded
| Term | What it means |
|---|---|
| GS / MSD | Gestational sac and its mean diameter — the fluid-filled sac, the first structure visible |
| YS | Yolk sac — a small ring inside the gestational sac, an expected early finding |
| FP / CRL | Fetal pole and crown-rump length — the embryo and its measured length, the most accurate way to date an early pregnancy |
| FH / FHR | Fetal heart and heart rate in beats per minute |
| EDD | Estimated date of delivery, calculated from the measurements |
| Intrauterine | The pregnancy is inside the womb, where it should be |
| Adnexa | The ovaries and surrounding structures — usually reported as normal |
| Corpus luteum | The structure left in the ovary after ovulation; it supports the pregnancy early on and is a normal finding |
| Subchorionic haematoma | A small collection of blood next to the sac — common, often resolves, and usually needs monitoring rather than treatment |
Why dates can shift — and why “too early” is not bad news
Early pregnancy has a sequence, and it is driven by how far along you are rather than by anything you can influence. The sac appears first, then the yolk sac, then the fetal pole, then the heartbeat. Each has a window, and being scanned before that window simply means the structure is not visible yet.
This is why a report may say a repeat scan is advised in a week or two. That is not a euphemism for bad news — it is the standard, correct response to scanning early, particularly if your cycles are long or irregular and your dates are uncertain. A pregnancy that measures smaller than expected is very often a pregnancy that is simply earlier than expected.
The dating measurement itself is precise early on: crown-rump length in the first trimester dates a pregnancy more accurately than the date of your last period, which is why an EDD from a scan sometimes differs from the one you calculated.
What this scan is and is not
An early pregnancy scan answers a specific set of questions: is the pregnancy in the womb, how far along is it, is there a heartbeat, and how many are there. Those are the questions that matter most in the first weeks.
It is not an anomaly scan. Assessment of the baby’s structure and organs happens at around 20 weeks, and combined screening for chromosomal conditions happens at around 12 weeks — both provided through the NHS pathway your midwife arranges. We do not offer NHS screening scans, and a private early scan does not replace or delay any part of that pathway.
Symptoms that need urgent care in early pregnancy
Severe one-sided abdominal or pelvic pain, heavy bleeding, shoulder-tip pain, faintness or collapse need same-day assessment — contact your nearest Early Pregnancy Unit, call NHS 111, or go to A&E. These can indicate an ectopic pregnancy, which is a medical emergency and not something to wait on.
Your questions answered
My report says no fetal pole seen. What does that mean?
Why does my EDD differ from my own calculation?
What is a subchorionic haematoma?
Is a heart rate of 120 too slow?
Does this scan check for Down’s syndrome or abnormalities?
When will I get my report?
Explained as we scan, written down clearly
Location, dating, heartbeat and number — talked through on screen at the appointment, with a written report usually within two hours that your midwife or GP can act on.
Kensington, London W8 4ED
3 mins from Notting Hill Gate
This article is general information about early pregnancy scan reports, not individual medical advice. Severe pain, heavy bleeding or faintness in early pregnancy needs same-day assessment via an Early Pregnancy Unit, NHS 111 or A&E — see NHS guidance on pregnancy and ectopic pregnancy. We do not provide NHS combined screening or the 20-week anomaly scan.
Written and clinically reviewed by the HCPC-registered sonographers who perform this scan at IUS London — a CQC-registered diagnostic ultrasound clinic (Provider ID 1-2775844974). Your own findings are explained to you at the scan and set out in your report.
Author: Yianni Kiromitis, Senior Sonographer, HCPC RA38415 — over 20 years’ experience in NHS and private ultrasound
Medically reviewed: 9 August 2026
