Obstetrics Scan

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The focus of ultrasound during pregnancy will depend on different trimester.

 

A )  First trimester scan

• This is also known as dating scan, viability scan, early pregnancy assessment or early pregnancy scan.

• During the first trimester you will need a full urinary bladder or at least partial filled urinary bladder to allowed better image formation.

• The medical Sonographer will put some conducting gel on your tummy. Then a small hand-held transducer will be used and rolled over your tummy to get the many views of your baby.

• Sometimes you may need a clearer view and the sonographer will used a transvaginal ultrasound probe to capture the image. This is  particularly so in the early weeks of pregnancy. Transvaginal ultrasonography is useful if you are overweight or your uterus is very deep in the pelvis (the bladder need to be emptied during the transvaginal ultrasound).

 

Ultrasound scan is used in early pregnancy to detect the following situation:

• Confirmation of pregnancy and it’s location whether intrauterine or extrauterine

• Evaluate suspected ectopic pregnancy

• Determination of placenta position

• Detection of numbers of embryos, pregnancy sac and multiple pregnancies

• Assess viability of embryo

• Assess gestational age

• Detect early pregnancy failure

• Diagnose fetal anomalies

• Assess fetal growth

• Assess associated maternal abnormalities such as ovarian cysts, fibroid

 

Transvaginal Scan

 

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Multiple Pregnancy

 

 

 

 

 

 

 

 

 

 

 

 

 

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Ectopic Pregnancy

Sometimes, the pregnancy might not implant within the endometrial cavity inside the uterus (mother womb). The ectopic pregnancy implant in the fallopian tube, ovary, abdominal cavity, or cervical region. Subsequently, the ectopic pregnancy will ruptured through the tube and cause bleeding which can be fatal if not detected early.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Transvaginal Ultrasound images of a living embryo in a tubal ectopic pregnancy

 

Ovarian Ectopic Pregnancy

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A Cornual Ectopic Pregnancy (The sac is positioned unfavourably high in the uterus where the fallopian tube joins)

 

 

Observations & measurements during first trimester pregnancy

 

i)  Measurement of gestational age by Crown-rump length (CRL)

In order to estimate the fetal gestational age, the Crown-rump length (CRL) of fetal is measured from head to buttock. The CRL is detectable at gestational age of 7 weeks.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Crown-rump length (CRL) of a fetus measured 41.6mm indicated of gestational age at 11 weeks 1 day. The head, body and limbs are clearly seen.

 

ii) Nuchal Translucency Thickness

The Nuchal Translucency at the back of the neck is due to the edema beneath the skin at the nuchal region (behind fetus neck). This is an important marker to detect abnormality of the fetus such as Down syndrome (trisomy 21), patau syndrome (Trisomy 13), Edward syndrome trisomy 18. The nuchal thickmness should not be more than 3mm.

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iii) Nasal bone (NB)

The present or absent of fetal nasal bone is an important marker for aneuploidy (abnormalities in chromosome). The fetus may encounter problem of hypoplastic or absent nasal bone.

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                    Normal nasal bone

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iv) Fetal Heart Rate (FHR)

Fetal heart rate measured to ensure baby's heartbeat within normal range.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fetal heart rate measured in beat per minutes (bpm)

 

 

Placental localization 
Ultrasonography has become indispensible in the localization of the site of the placenta and determining its lower edges, thus making a diagnosis or an exclusion of placenta previa. Other placental abnormalities in conditions such as diabetes, fetal hydrops,Rh isoimmunization and severe intrauterine growth restriction can also be assessed.

 

 

 

 

 

 

 

 

 

 

B ) Second trimester scan

This is also known as Fetal Anomaly Scan, Detailed Scan or a 20 week scan.
Please click here for Fetal Anomaly Scan. 

 

C ) Third trimester scan

This is also known as Fetal Well Being Scan

• Perform from 24 weeks-to term

• To assess baby's position

• To assess baby's growth

• To assess placenta position

• To assess amniotic fluid volume

• To perform Doppler studies

 

 

 

 

 

 

 

 

 

 

 

 

 

This photo shows Colour Doppler on both the normal renal arteries

 

 

 

 

 

 

 

 

 

 

 

This photo shows Colour Doppler on normal umbilical cord

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