When do you have a target scan when pregnant?
A target scan is one of the most important prenatal ultrasound scans and helps assess the fetus's development and location, and detects any impairments.

Target scan is also known as targeted imaging for fetal anomalies scan or fetal anomaly scan. This scan is an important and required prenatal ultrasound screening during the second trimester of pregnancy and is normally done between 18 and 20 weeks of gestation. However, you can have an early target scan at 16 weeks of pregnancy.

This scan focuses on monitoring the baby's physical development, growth, and how the infant is doing, as well as finding any anatomical abnormalities.

3 main objectives of a target scan

Three main objectives of a target scan include:

  1. To predict the baby's structural integrity within reasonable boundaries of expectation
  2. To detect serious and potentially fatal anomalies
  3. To suggest the possibility of an abnormality, which requires more testing or serial scans

Target scan examines each element of your child's natural and healthy growth. The scan can detect significant abnormalities in the fetus, but it cannot detect all defects. In the scan, your baby may appear totally healthy. However, there is always a possibility that the baby may be born with defects.

12 most commonly detected abnormalities in a target scan

Twelve most commonly detected abnormalities in a target scan include:

  1. Anencephaly (98 percent): This is a life-limiting condition in which the brain and skull bones grow abnormally. Unfortunately, newborns with this condition cannot live after they are born and die soon after. Incidence is 1 in 2,000 babies.
  2. Gastroschisis (98 percent): This is a defect or “hole” in the abdominal wall of the newborn to one side of the umbilical cord (usually the right side). Intestine escapes through this opening and grows outside of the baby's abdomen. Newborns cannot survive and die soon after. Incidence is 1 in 2,000 babies.
  3. Patau’s syndrome (Trisomy 13) (95 percent): This is a rare hereditary chromosomal disease in which a newborn has three copies of chromosome 13 rather than the typical two. Incidence is 1 in 4,000 babies.
  4. Edwards’ syndrome (Trisomy 18) (95 percent): This is a rare hereditary chromosomal disease in which a newborn has three copies of chromosome 18 rather than the typical two. Incidence is 1 in 1,500 babies.
  5. Open spina bifida (90 percent): Spina bifida occurs when your baby's spinal cord does not grow normally, resulting in a gap or split in the spine. Incidence is 1 in 1,666 babies.
  6. Bilateral renal agenesis (84 percent): Bilateral renal agenesis is a self-limiting condition in which your baby's kidneys have not yet formed. Unfortunately, kids with this disease die soon after birth because they cannot survive without the kidneys. Incidence is 1 in 5,000 babies.
  7. Exomphalos (80 percent): Exomphalos occur when the abdomen fails to close around the umbilical cord's base during the baby's early development. This indicates that certain organs emerge from the baby's abdomen. Incidence is 1 in 2,500 babies.
  8. Cleft lip (75 percent): This occurs when some components of your baby's face, notably the lips, do not connect properly. Incidence is 1 in 1,300 babies.
  9. Lethal skeletal dysplasia (60 percent): Skeletal dysplasia is a complex group of bone and cartilage disorders that may affect the fetal skeleton as it develops in utero. Incidence is 1 in 10,000 babies.
  10. Congenital diaphragmatic hernia (60 percent): This occurs when your baby's diaphragm does not fully develop. The diaphragm is a muscle that helps humans breathe and separates the heart and lungs from the intestines and the rest of the abdominal organs. Incidence is 1 in 2,500 babies.
  11. Congenital heart diseases (50 percent): These include a variety of cardiac defects such as the chamber, valve, or vessel defects, which indicate that your baby will require medical treatment soon after delivery. Incidence is 1 in 125 where 1 in 500 babies have a critical defect.
  12. Down syndrome (Trisomy 21) (50 percent): This is a genetic disorder in which a newborn has a complete or some parts of the third copy of chromosome 21 rather than the typical two. Incidence is 1 in 700 babies.

SLIDESHOW

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Reasons for missing identification of abnormalities during a target scan

Common reasons for missing the identification of some anomalies during an ultrasound scan include:

  • The fetal position is not ideal to identify all parts of the body
  • Mother is overweight
  • Presence of fibroids that obstruct the view 

In such cases, another scan at 23 weeks is done. If the scan cannot be completed at 23 weeks, which is extremely rare, your baby will get a full physical examination and testing following birth.

How is the target scan done?

The scanning procedure is carried out swiftly and painlessly by skilled medical personnel. The sonographer or radiologist will first apply the gel to your belly. The probe is then moved around the region to be studied with a handheld probe. The gel used helps the probe make excellent contact with your skin.

On the ultrasound screen, you will view images of your baby. To obtain clear photos of your baby, the sonographer may apply slight pressure to your abdomen while repositioning the probe, which may be painful. Nonetheless, it is completely safe and done with caution.

  • The complete procedure lasts between 30 and 40 minutes. However, it may be delayed if your baby moves a lot or if a sonologist is unable to check any area of the infant in depth owing to the baby's posture.
  • The sonologist may ask you to wait some more time till the baby shows the right position or may call you back another day to inspect it.
  • You may be asked to drink plenty of water before the scan because a full urinary bladder will provide a better view; however, it is not required all the time.

How to prepare for a target scan

The following are a few things to remember before visiting a sonologist for an abnormality scan:

  • Carry your obstetrician's sonography prescription with you.
  • Bring your prior ultrasound scan records with you. Before doing the anomaly scan, the doctor may choose to consult with them.
  • An anomaly scan does not require having a full bladder.
  • Allow enough time while doing an anomaly scan. This scan may take longer than others, so don't rush.

What is the importance of a target scan?

The target scan is one of the most important prenatal ultrasound scans.

  • This scan is performed to assess the fetus's development and location, as well as to detect any impairments.
  • This scan aids in the detection of anomalies and, in certain extreme cases, allows you to decide whether to continue the pregnancy.

As with many pregnancy exams and treatments, this one is also a personal choice for the woman. However, all prenatal experts strongly suggest this scan.

The target scan is done between 18 and 20 weeks of pregnancy because the baby grows around six inches by the 19th week of pregnancy. Several anatomical structures and internal organs begin to develop and mature, so the target scan captures any abnormalities in the fetus.

Although many abnormalities are not detectable during sonography, about 50 percent of Down syndrome problems and congenital heart defects are identified.

  • The target scan evaluates the fetus from the head to toe, checking general growth, development, and health. The sonographer evaluates the baby's anatomy and any structural issues.
  • The scan can determine the fetus's size and weight. Moreover, it considers the location of your placenta, umbilical cord, and amniotic fluid surrounding the fetus. 
  • Any improper location of the placenta during pregnancy can result in miscarriages or severe bleeding, as well as a variety of issues for both the mother and infant.

In certain circumstances, the baby's organs do not grow normally. Some may result in the death of the fetus anytime during the pregnancy or shortly after birth. All of this must be discovered, investigated, and analyzed beforehand. This scan allows your obstetrician to provide the appropriate steps, medications, and reassurance about your baby's health for the remaining days of your pregnancy.

Things to know about a target scan

  • Numerous scientific studies have offered reassurance that ultrasound imaging is safe when used with caution by well-educated experts on adults, children or the human fetus or embryo. 
  • The sonographer may identify and notify you about the sex of the baby. However, the identification of gender might be incorrect in one to three percent of the cases. Therefore, you must embrace the potential of being told the wrong sex.

QUESTION

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Medically Reviewed on 5/4/2022
References
Image Source: iStock Image

Second trimester ultrasound scan: https://radiopaedia.org/articles/second-trimester-ultrasound-scan

Target Scan-The Experience at Saveetha Medical College: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3681058/

Level II Ultrasound: https://www.webmd.com/baby/level-ii-ultrasound

Targeted Obstetric Ultrasound https://emedicine.medscape.com/article/2047105-overview