Ultrasound Pregnancy Questions & Answers

When is the ideal time for a 4D Ultrasound Scan?
4D Ultrasound scans are performed any time from 12 weeks. The timing depends on what stage of development the parents would like to view their baby. Its always a good idea to start scanning earlier and follow through to later stages. Early pregnancy scans demonstrates full body foetal views with detailed bony anatomy and movement. As the pregnancy progresses, images will display separate views of the face, legs, arms, gender etc. The layers of muscle and fatty tissue increases in thickness and facial character becomes more evident. Babies are often seen yawning, blinking, waving and swallowing. 3rd Trimester 4D Scans display a striking resemblance to the baby at birth. The best images are obtained when there is sufficient fluid and no obscuring structures causing image distortion. If the baby chooses to hide, many techniques will be performed to try and change position. Baby’s performance is unpredictable so ideal images can never be guaranteed.
Guideline: 12-15 weeks, 16-20 weeks, 20-26 weeks, 26 weeks-30 weeks, 30 weeks-34 weeks,34 weeks-38 weeks.
Start 4D Scans early and follow up in 4D later – It’s best!

What is the difference between 2D, 3D and 4D scans?
-2D scans are black and white scans capable of seeing the baby’s bone structure as well as soft tissue. Measurements, gender and abnormalities can be detected with 2D scans but a trained eye is necessary. The scan is also real-time so that movement can be viewed.
-3D reconstructions are 3 planes which is able to map the foetus with incredible detail producing lifelike images which are easily recognized by the general public. It adds background colour, texture and shadows thus bringing the image to life.3d on its own is outdated technology and is combined with 4D Technology.
-4D scan adds real-time to the 3D image so that movement of baby is observed. 4D is a valuable adjunct to 2D and will never replace 2D scans. Abnormalities noted on 2D can be confirmed with 4D technology.

When is the earliest time to determine gender?
Gender is theoretically determined from 13 weeks and confiemed from 15 weeks
Technical factors that play a role at this stage. These factors are:
1. Mums weight -large/overweight mum’s result in poor image quality.
2. Foetal position- naturally we need a good view of the “area”. Most foetuses cooperate but some DON’T.
3. Foetal health- eg. low amniotic fluid or foetal abnormality can result in poor image quality.

What abnormalities can be diagnosed with ultrasound scans?

  • Neural tube defects: hydrocephalus, anencephaly, encephalocoele, spina bifida, meningocoele, cystic hygroma, sacrococcygeal teratoma, microcephaly, holoprosencephaly, sirenomelia, sacral agenesis,
  • Cardiac: ectopia cordis, pericardial effusion, VSD, hypoplastic heart, great vessel transposition, myocardial tumours, aortic stenosis, arrhythmia,
  • Abdominal wall: gastrochisis, omphalocoele, ascites, duodenal/jejuna atresia, diaphragmatic hernia, cloacal bladder, hepatomegaly, splenomegaly, ascites,
  • Renal tract: hydronehrosis, polycystic kidney, unilateral kidney, megacystis,
  • Genitalia: ambiguous genitalia, ovarian cyst, scrotal hydrocoele, cliteromegaly, hypospadia, hydrometrocolpos,
  • Limbs: micromelia(dwarfism), polydactyly, syndactyly, talipes(club foot), thanatophoric dysplasia, osteogenises imperfecta, IUGR(growth deformity)
  • Facial: cleft palate/lip, micrognathia, proboscis, Cyclops, hypertelorism, hypotelorism,
  • Twins: co-twin demise, IUGR, TTS, conjoined(Siamese twins), acardiac monster, stuck twin phenomenon.

What abnormalities cannot be diagnosed with ultrasound scans?
Autism, cerebral palsy, deafness, blindness and genetic disorders such as Down’s Syndrome if there are no associated markers. Therefore a normal scan cannot guarantee a normal baby at birth. Due to technical challenges, abnormalities can be overlooked or difficult to confirm.

What is an anomaly pregnancy scan?
An anomaly scan is a detailed anatomical survey of the baby’s bone, soft tissue and organ development. In addition to routine measurements, the scan investigates the possibility of structural birth defects and signs of genetic disorders. The results are immediate and a diagnostic report will be issued.

Are an anomaly pregnancy scans accurate?
Ultrasound is operator dependent. An experienced, skilled operator is likely to produce diagnostic accuracy but ultrasound cannot diagnose 100% of congenital abnormalities. Some abnormalities are too subtle and some disorders cannot be seen on ultrasound at all.

What if the scan detects a problem?
Such cases will be offered strict confidentiality and referral management. We work alongside a network of Fetal Specialists, Gynaecologists, Public Hospitals, Pathologists, General Practitioners, and Midwives to function as a team in providing effective obstetric care.
Depending on the findings the parent/s will be offered the following:
• Referral to a foetal specialist or gynaecologist.
• Detailed report to the antenatal clinic or midwife.
• Referral with further investigation via an amniocentesis, cordocentesis, chorionic villis sampling (CVS).
• Referral to a geneticist for counselling and management.
• Minor abnormalities will need ultrasound surveillance and possibly Doppler of the umbilical arteries.
• Severe abnormalities or incompatibility with life may be offered a termination by the specialist.

Are ultrasound scans safe?
• Ultrasound is safe, affordable, non-invasive and uses no ionizing radiation or light but rather high frequency waves which neither mum or baby can hear.
• Ultrasound generates heat (than 1 degree centigrade) which is absorbed by the body tissue that is being scanned. Long scanning times can raise tissue temperatures and cause potential harm. We adhere to the ALARA principle (as low as reasonably achievable) in time, scanning technique as well as machine output settings and controls to achieve benefit rather than risk to the patient.

How long are the sessions?
Our scans are quality focused rather than quantity based. Scan times should never exceed 20-25 minutes unless in the case of high risk pregnancy.

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