Pregnancy Ultrasound Scan

Ultrasound uses high frequency sound waves beyond the range of human hearing to produce images of your uterus and pelvic organs. Sound waves are produced and transmitted into the body from a hand-held probe.  For pregnancy scans, the probe is either pressed gently into the lower abdominal wall or else you will be asked to insert a special internal probe.  The sound waves are reflected by the tissues back to the probe and processed by the ultrasound machine's computer to form diagnostic images of remarkable clarity. Ultrasound can be used to scan pregnancies for a wide variety of reasons from 3 weeks after conception until after the baby is due.  For information on 3D and 4D scans, please advance to this section.

 Please Note:

Whom to bring with you? You are welcome to bring your partner or other family members with you to watch the scan. However, please be aware that obstetric scans are complex and lengthy examinations, requiring  the sonographer to concentrate hard if he/she is to perform their job well. We therefore recommend having no more than 2 accompanying persons with you, and to avoid bringing young children if possible. If unavoidable, please ensure that you have someone present to supervise your children as necessary.

How long will it take? Routine pregnancy scans generally take 30 minutes but please allow a little extra time due to unforeseeable delays. For detailed fetal cardiac scans, please allow an hour.

How much will it cost?  The NZ Government subsidises scans performed for authorised indications.  The list of indications can be seen here.  For subsidised scans, there is still a surcharge to the patient of $50.  For scans that fall outside the allowed indications, the patient must pay the full fee.

 First Trimester Pregnancy scan (less than 12 weeks)

Preparation:  Try to have a  full bladder for your scan. We recommend that you empty your bladder 2 hours prior to the scan then drink 2 glasses of water and do not empty the bladder after that.

An internal (transvaginal) scan is often recommended as it may provide a clearer view in early pregnancy. After you have given your consent, you will be asked to insert a small sterilised probe covered by a disposable protective sheath into your vagina. It should not be painful. Please inform the sonographer or radiologist immediately if you experience discomfort. Your privacy will be respected at all times during the examination. Your referring doctor or midwife may have requested the scan if you have experienced pain or bleeding in the pregnancy or have had a previous miscarriage or ectopic pregnancy.

The scan allows us to: 

• Accurately date the pregnancy. This is particularly important for women who do not know the date of their last period, have an irregular menstrual cycle, or who have conceived whilst breastfeeding or soon after stopping the oral contraceptive pill. We measure the crown-rump length (size) of the embryo and from this we can calculate the expected date of delivery.
• Determine the number of embryos present
• Determine whether the pregnancy is progressing normally inside the uterus.

11 – 13 week Pregnancy (Nuchal Translucency) scan

Preparation: It is helpful to have a full bladder for this scan. We recommend that you empty your bladder 2 hours prior to the scan then drink 2 glasses of water and do not empty the bladder after that.

The scan is usually performed transabdominally but occasionally it may be necessary to do the examination transvaginally.

The scan allows us to: 

• Date the pregnancy accurately. This is particularly relevant for women who do not know the date of their last period, have an irregular menstrual cycle, or who have conceived whilst breastfeeding or soon after stopping the oral contraceptive pill. We measure the crown-rump length (size) of the fetus and from this we calculate the expected date of delivery. 
• 
  Perform a risk assessment for Down syndrome and other chromosomal abnormalities. An individual risk for the pregnancy is calculated by taking into account the age of the mother and the nuchal translucency thickness. These results may be combined with a blood test to give a slightly more accurate risk assessment. We recommend that you discuss the range and implications of these tests thoroughly with your lead maternity carer before your scan. Risk assessment for Down syndrome risk can only be performed between 11 and 13 weeks, 6 days, using specialised software from the Fetal Medicine Foundation.
• 
  Diagnose multiple pregnancy. Approximately 2% of natural conceptions and 10% of assisted conceptions result in multiple pregnancy. Early ultrasound scanning allows us to determine whether the babies share the same placenta which increases the risk and may require closer monitoring throughout the pregnancy.

• Diagnose certain major fetal abnormalities or early pregnancy failure. 

Risk of Down syndrome

It is important to remember that the vast majority of babies born are normal. However all women, regardless of their age, have a small risk of delivering a baby with a physical and/or mental handicap.

In some cases the handicap is due to chromosomal abnormality such as Down syndrome.

Non-invasive screening for Down syndrome may be performed at the 11-13 week scan by measuring the nuchal translucency, and entering this measurement into risk assessment software from the Fetal Medicine Foundation. The age of the mother and the nuchal translucency measurement may be used to generate an individual risk for the pregnancy. Additional blood tests to measure hormones in the mother’s blood can be combined to generate a slightly more accurate risk assessment.

Please note that nuchal translucency is a screening test, not a diagnostic test, for chromosomal abnormality. The only way to know for certain whether or not the fetus has a chromosomal abnormality is by having an invasive test such as chorionic villus sampling (CVS) or amniocentesis (amnio). However, these tests carry a risk of miscarriage of about 1%.

We recommend that you discuss the options of screening tests available to you thoroughly with your LMC (lead maternity carer).

 Other causes for increased nuchal translucency

Many babies with increased nuchal translucency have no abnormalities at birth. Down syndrome is just one of the known causes for increased nuchal translucency in the fetus. There are many other conditions associated with increased nuchal translucency, including cardiac abnormalities.  If your fetus has increased nuchal translucency, you will be offered referral for counselling and an invasive test such as CVS or amniocentesis. We will also recommend that the fetal heart be examined very carefully, usually at the time of your routine anatomy scan (at 18 – 20 weeks).

 Second trimester Pregnancy (Anatomy) scan

Preparation: No specific preparation is necessary. It is not necessary to have a full bladder for this scan.The scan is usually performed transabdominally.

This is a detailed scan best performed at 18-20 weeks of pregnancy, in which we examine your baby’s anatomy (such as the brain, face, spine, heart, stomach, bowel, kidneys and limbs) and growth. The position of the placenta is documented.

      Cardiac scan (detailed fetal echocardiography)

Preparation:  No specific preparation is necessary. It is not necessary to have a full bladder for this scan.

This scan may have been recommended by your midwife or doctor if you have diabetes, a family history of heart abnormalities, or if the nuchal translucency thickness was increased at the 11-13 week scan. A detailed examination of the fetal heart and connecting vessels is performed by an experienced sonographer with special expertise in this area. It can usually be performed at 18-20 weeks in conjunction with the anomaly scan, but occasionally a follow up scan may be recommended at 22-24 weeks.

Third trimester Pregnancy (growth) scan

Preparation:  This ultrasound scan is usually performed between 28 and 32 weeks of pregnancy. No specific preparation is necessary. It is not necessary to have a full bladder for this scan.

This scan is particularly important in women who have had previous complications of pregnancy such as pre-eclampsia, growth restriction, diabetes, or stillbirth, and for those women who develop a problem during the course of their current pregnancy. If the placenta was found to be low at the time of the 18-20 week scan we would recommend a check in the third trimester. This scan allows us to assess the growth and wellbeing of the fetus by:

•         Measurement of the size of the fetal head, abdomen and femur and calculation of the current fetal weight
• Examination of fetal movements
• Evaluation of the position and appearance of the placenta
• Measurement of amniotic fluid volume
• Assessment of blood flow to the placenta and fetus using colour Doppler ultrasound  
  

Results

Your scan will be read and reported by a radiologist. A copy of the report will be sent to your midwife and/or doctor.  The images, report, sonographer measurements and graphs will be stored long term in our digital archives and available at all times to your midwife and doctor.  You will be offered a high resolution paper print of an image at the time of your scan and the opportunity to receive this image by email, all at no charge.  You may also receive a CD of the full scan at an extra cost of $16. Please discuss with the sonographer during your scan.

SECTION 88 CLINICAL INDICATIONS

Please ensure the following two letter codes are used for pregnancy scans