The ultrasound examination should not be used as a substitute for a pregnancy test.
- State clinical concern and reason for examination;
- State the patient’s LNMP if known, and date of 1st positive pregnancy test;
- Relevant history – maternal conditions, parity, pregnancy loss, assisted conception,congenital abnormalities; and
- Relevant clinical examination.
Indications for Ultrasound <12 Weeks Gestation(Refer to Appendix 4 – Indications for Ultrasound <12 Weeks Gestation for complete list)
There are many common clinical indications for an ultrasound examination <12 weeks, with the main aim to assess:
- Pregnancy location;
- Gestational age;
- Number of fetal poles;
- Presence of fetal cardiac activity;
- Trophoblastic disease; and
- Pelvic masses and uterine malformations.
The Ultrasound Examination
- In the majority of cases, particularly pregnancies <8 weeks gestation, both transabdominal and transvaginal scanning will be required;
- The position of the gestational sac should be stated and measured in 3 planes and an average of three measurements taken from two planes;
- The yolk sac should be documented and measured;
- Once a fetal pole is present the CRL will form the measure of gestational age. This should be measured and clearly stated;
- Fetal heart rate noted and rate recorded;
- Fetal movement noted;
- Any intracavity bleed should be documented;
- Both ovaries should be assessed and the site of the corpus luteum should be stated;
- Any uterine and adnexal masses should be assessed and described in detail;
- Uterine shape should be assessed;
- If a multiple pregnancy is present, the chorionicity, number of fetal poles and yolk sacs should be stated; and
- Depending on the stage of pregnancy, position and nature of developing placental tissue noted.
The Report and Criteria for Assessment
- Record if transabdominal and/or transvaginal scan performed.
- Clinical history and indication for examination. LNMP or EDD by dates.
- Dating: If a fetal pole is present, the CRL used for gestational age calculation is recorded. If no fetal pole is present, the mean gestational sac diameter is used to assess gestational age. Presence or absence of a yolk sac should be noted when a fetus is not seen. Calculate EDD by Ultrasound if more than 4 days different from EDD by dates.
- Fetal Viability: Transvaginal Scanning is recommended in all pregnancies of <8 weeks gestation if no fetal heart motion can be recorded transabdominally:
(Refer to Appendix 5 - ASUM Guidelines for the Performance of First Trimester Ultrasound.)
If the above criteria are not present, i.e. pregnancy is < 6 weeks gestation, a repeat ultrasound in 7 days may be recommended in the report.
If fetal viability is confirmed but PV bleeding persists or worsens, reassessment may be indicated.
- Ectopic Pregnancy: Uterine cavity appearance, ovarian appearance and site of corpus luteum, presence, size and site of the suspected ectopic, presence of peritoneal fluid including under the diaphragm. Correlation with quantitative bHCG recommended.
- Multiple Pregnancies: Chorionicity should be reported and is most accurately assessed during the 1st trimester. Two completely separate gestational sacs confirm a dichorionic twin pregnancy. The CRL and FHR of each twin should be stated. If there is only one gestational sac, the pregnancy is monochorionic and in these cases, the yolk sac and amnion should be clearly assessed. If there are two separate yolk sacs and a separating amnionic membrane, the pregnancy is monochorionic/diamniotic. If there is only one gestational sac with only one yolk sac, and a single amniotic cavity, the pregnancy is monochorionic/monoamniotic.
- Gestational Trophoblastic Disease: A molar pregnancy is suspected in the presence of cystic hydropic change to placental tissue.
- Uterine and adnexal Masses – Describe the dimension, nature and location of the mass. Presence of free fluid.