Obstetric Ultrasonography — MCQs
Which of the following sonographic findings is most indicative of an intrauterine pregnancy?
A woman presents to you at 36 weeks of gestation with complaints of breathlessness and excessive abdominal distension. Fetal movements are normal. On examination, fetal parts are not easily felt and fetal heartbeat is heard but it is muffled. Her symphysis fundal height is 41 cm. Her abdomen is tense but not tender. What is the most likely diagnosis?
What is the best parameter for estimating fetal age by ultrasound in the third trimester?
In current obstetrics practice, what is the best test for monitoring sensitized Rh negative mother?
What condition is associated with the sign seen in the given USG?
A woman has been using oral contraceptive pills (OCP) for 5 months and has had amenorrhea for the last 6 weeks. What is the best method to calculate the gestational age in this case?
A 28-year-old primigravida at 32 weeks of gestation presents for a routine prenatal visit. She has no significant past medical history. During the ultrasound examination, various parameters are assessed to evaluate fetal growth and well-being. Which of the following is NOT a criterion used to diagnose Intrauterine Growth Restriction (IUGR)?
Banana sign is seen in which of the following conditions?
On Doppler, the most ominous sign indicating fetal compromise is:
18 weeks pregnant female presents with no high risk of NTD and low risk of trisomy 21 on quad test. What is the most appropriate next step in management?
Obstetric Ultrasonography Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following sonographic findings is most indicative of an intrauterine pregnancy?
- A. A double decidual sign with two concentric echogenic rings.
- B. A gestational sac with a yolk sac. (Correct Answer)
- C. A gestational sac without any accompanying structures.
- D. An echogenic rim along one side of the decidua.
Explanation: ***A gestational sac with a yolk sac.*** - The presence of a **yolk sac** within a **gestational sac** definitively confirms an **intrauterine pregnancy (IUP)**, as a yolk sac is fetal tissue. - This finding is typically visible around **5-6 weeks gestational age** via transvaginal ultrasound. *A double decidual sign with two concentric echogenic rings.* - The **double decidual sign** is suggestive of an IUP but is not definitive, as it can occasionally be mimicked by a **pseudogestational sac** in **ectopic pregnancies**. - It represents the decidua parietalis and decidua capsularis, which are maternal tissues. *A gestational sac without any accompanying structures.* - A **gestational sac without a yolk sac** is often referred to as a **"fluid-filled sac"** and can be present in both normal early IUPs and **pseudogestational sacs** of ectopic pregnancies. - While it warrants follow-up, it is not definitive for an IUP on its own. *An echogenic rim along one side of the decidua.* - This description is too vague and does not provide specific enough details to indicate an intrauterine pregnancy. - It could be a normal endometrial fold or an artifact, but lacks definitive embryonic structures.
Question 2: A woman presents to you at 36 weeks of gestation with complaints of breathlessness and excessive abdominal distension. Fetal movements are normal. On examination, fetal parts are not easily felt and fetal heartbeat is heard but it is muffled. Her symphysis fundal height is 41 cm. Her abdomen is tense but not tender. What is the most likely diagnosis?
- A. Abruptio placenta
- B. Hydrocephalus of fetus
- C. Polyhydramnios (Correct Answer)
- D. Oligohydramnios
Explanation: ***Polyhydramnios*** - The patient's symptoms of **breathlessness**, **excessive abdominal distension**, a **symphysis fundal height of 41 cm at 36 weeks** (indicating a significantly larger than expected uterus), and **muffled fetal heart tones** are classic signs of polyhydramnios. - **Difficulty feeling fetal parts** is also consistent with excess amniotic fluid, which cushions the fetus and makes palpation harder. *Abruptio placenta* - This condition typically presents with sudden onset of **painful vaginal bleeding**, uterine tenderness, and fetal distress, none of which are described here. - While the abdomen might be tense due to uterine contractions or concealed bleeding, the lack of pain and bleeding makes this diagnosis unlikely. *Hydrocephalus of fetus* - Fetal hydrocephalus would primarily manifest as an **abnormally large fetal head** upon ultrasound, potentially leading to a higher fundal height. - However, it wouldn't directly explain the generalized excessive abdominal distension or the difficulty in feeling fetal parts due to fluid, though it could be a cause of polyhydramnios itself, it is not the most likely primary diagnosis from the given options directly addressing the symptoms. *Oligohydramnios* - This condition is characterized by **too little amniotic fluid**, which would result in a **smaller than expected symphysis fundal height** and an easily palpable fetus. - The patient's symptoms, particularly the excessive distension and high fundal height, directly contradict the features of oligohydramnios.
Question 3: What is the best parameter for estimating fetal age by ultrasound in the third trimester?
- A. Abdominal circumference
- B. Femur length
- C. Intraocular distance
- D. BPD (Correct Answer)
Explanation: ***BPD (Biparietal Diameter)*** - **Biparietal diameter (BPD)** is considered the **best single parameter** among the given options for estimating fetal age in the third trimester, though all parameters become less accurate with advancing gestation. - In the third trimester, BPD accuracy is approximately **±3-4 weeks**, which is why **first trimester dating (CRL) should always be used when available** as it is most accurate (±5-7 days). - BPD is measured at the level of the thalami and cavum septum pellucidum, from outer edge of the proximal skull to the inner edge of the distal skull. - **Note**: Multiple biometric parameters used together improve accuracy more than any single measurement in late pregnancy. *Femur length* - **Femur length (FL)** is highly accurate in the **second trimester** but becomes less reliable in the third trimester due to biological variation. - It can be affected by **skeletal dysplasias** and genetic factors, leading to inaccurate age estimation. - FL is better used for assessing proportionate growth rather than dating in late pregnancy. *Abdominal circumference* - **Abdominal circumference (AC)** is primarily used for assessing **fetal growth and estimating fetal weight**, not for gestational age determination. - It is highly variable and influenced by fetal nutritional status, growth restriction, or macrosomia, making it unreliable for dating. - AC is the **most sensitive parameter for detecting growth abnormalities** (IUGR or LGA). *Intraocular distance* - **Intraocular distance (IOD)** is not a standard biometric parameter for routine gestational age estimation. - It has limited clinical utility and is occasionally used for detecting specific **fetal anomalies** (hypertelorism/hypotelorism) rather than dating. - Standard biometric parameters (BPD, HC, AC, FL) are always preferred for gestational age assessment.
Question 4: In current obstetrics practice, what is the best test for monitoring sensitized Rh negative mother?
- A. Biophysical profile
- B. Amniotic fluid spectrophotometry
- C. Middle cerebral artery Doppler wave forms (Correct Answer)
- D. Fetal blood sampling
Explanation: ***Middle cerebral artery Doppler wave forms*** - This is currently the most widely accepted and **non-invasive** method for monitoring **fetal anemia** in Rh-sensitized pregnancies. - An increase in the **peak systolic velocity (PSV)** in the middle cerebral artery indicates that the fetus is increasing cardiac output to compensate for a reduced oxygen-carrying capacity due to anemia. *Biophysical profile* - The biophysical profile assesses various fetal parameters like **movement**, **tone**, **breathing**, and **amniotic fluid volume**, which are often altered late in the course of severe fetal anemia. - It is a **less sensitive** indicator of early or moderate fetal anemia compared to MCA Doppler. *Amniotic fluid spectrophotometry* - This method measures the **bilirubin levels** in amniotic fluid, which correlates with the severity of hemolysis. - It is an **invasive procedure** (amniocentesis) and has largely been replaced by non-invasive MCA Doppler due to associated risks and better predictive value of Doppler. *Fetal blood sampling* - Fetal blood sampling (cordocentesis) provides a direct measurement of **fetal hemoglobin** and other blood parameters. - While definitive, it is a **highly invasive procedure** with significant risks, reserved primarily for confirmation of severe anemia or for direct transfusion, not for routine monitoring.
Question 5: What condition is associated with the sign seen in the given USG?
- A. Anencephaly
- B. Spina bifida (Correct Answer)
- C. Dandy-Walker malformation
- D. Encephalocele
Explanation: ***Spina bifida*** - The ultrasound image displays the **"lemon sign"** (frontal bone indentation), which is a classic indicator of **spina bifida** on antenatal ultrasound. - The lemon sign is caused by **scalloping of the frontal bones** due to caudal displacement of brain tissue (Arnold-Chiari malformation type II) secondary to an open spinal defect. - This sign is most commonly seen in the **second trimester** and is associated with neural tube defects. *Anencephaly* - **Anencephaly** presents with absence of the cranial vault and cerebral hemispheres on ultrasound. - The characteristic finding is the **"frog-eye appearance"** with protruding orbits, not frontal bone scalloping. - This is incompatible with life and has a distinctly different ultrasound appearance. *Dandy-Walker malformation* - **Dandy-Walker malformation** shows an enlarged posterior fossa with cystic dilatation of the fourth ventricle and hypoplasia of the cerebellar vermis. - It may present with the **"banana sign"** (cerebellar compression), but not the lemon sign. - This is a posterior fossa abnormality, not associated with frontal bone changes. *Encephalocele* - **Encephalocele** presents as a herniation of brain tissue and meninges through a cranial defect, typically occipital. - Ultrasound shows a **cystic mass protruding from the skull**, not frontal bone indentation. - While it's a neural tube defect, it has a different ultrasound appearance than the lemon sign.
Question 6: A woman has been using oral contraceptive pills (OCP) for 5 months and has had amenorrhea for the last 6 weeks. What is the best method to calculate the gestational age in this case?
- A. Abdominal girth
- B. 280 days from Last Menstrual Period (LMP)
- C. Crown-Rump Length (CRL) by Ultrasound (USG) (Correct Answer)
- D. 256 days from Last Menstrual Period (LMP)
Explanation: ***Crown-Rump Length (CRL) by Ultrasound (USG)*** - For women with **irregular menstrual cycles**, unknown last menstrual period, or those on **hormonal contraceptives**, **early ultrasound measurement of CRL** is the most accurate method for gestational age determination. - CRL is most accurate between **6 and 14 weeks of gestation**, providing a precise estimate within 3-5 days. *Abdominal girth* - **Abdominal girth** is an unreliable and highly variable measure that is not used for accurate gestational age determination. - It is influenced by maternal body habitus, uterine fibroids, and amniotic fluid volume, making it imprecise. *280 days from Last Menstrual Period (LMP)* - This method (Naegele's rule) assumes a **regular 28-day menstrual cycle** and ovulation on day 14, which is not applicable for a woman on **oral contraceptive pills (OCP)** where ovulation is suppressed. - The use of OCPs alters the hormonal profile, generally causing **amenorrhea or withdrawal bleeding** that does not reflect a true ovulatory cycle. *256 days from Last Menstrual Period (LMP)* - This calculation is not a standard or recognized method for determining **estimated date of delivery (EDD)**. - The standard calculation from LMP uses **280 days (40 weeks)** for a full-term pregnancy.
Question 7: A 28-year-old primigravida at 32 weeks of gestation presents for a routine prenatal visit. She has no significant past medical history. During the ultrasound examination, various parameters are assessed to evaluate fetal growth and well-being. Which of the following is NOT a criterion used to diagnose Intrauterine Growth Restriction (IUGR)?
- A. Fetal weight less than the 3rd percentile
- B. Abdominal circumference (AC) less than the 3rd percentile
- C. Uterine artery Pulsatility Index (PI) > 95th percentile (Correct Answer)
- D. Estimated fetal weight (EFW) below the 10th percentile for gestational age
Explanation: ***Uterine artery Pulsatility Index (PI) > 95th percentile*** - A **high uterine artery Pulsatility Index (PI)**, especially above the 95th percentile, is indicative of **increased vascular resistance** in the uteroplacental circulation. - While it suggests an **increased risk of IUGR** and other adverse pregnancy outcomes due to impaired placentation, it is a **risk predictor or screening tool, not a diagnostic criterion** for IUGR itself. - It helps identify high-risk pregnancies that require closer monitoring but does not diagnose IUGR. *Fetal weight less than the 3rd percentile* - This is a **direct diagnostic criterion** for severe IUGR, indicating significant growth restriction. - It signifies that the fetus is substantially smaller than expected for gestational age, reflecting a failure to meet its growth potential. *Abdominal circumference (AC) less than the 3rd percentile* - An **Abdominal Circumference (AC) below the 3rd percentile** is a **direct diagnostic criterion** for severe asymmetric IUGR. - The AC is a critical parameter as it reflects the fetal liver size and glycogen stores, which are reduced in growth restriction. - AC is often the first biometric parameter to show growth restriction in placental insufficiency. *Estimated fetal weight (EFW) below the 10th percentile for gestational age* - **EFW < 10th percentile** is the **most commonly used diagnostic criterion** for IUGR in clinical practice. - This threshold is widely accepted in international guidelines (ACOG, RCOG, ISUOG) for diagnosing IUGR. - Some centers use < 5th percentile or < 3rd percentile for severe IUGR, but the 10th percentile is the standard diagnostic cutoff.
Question 8: Banana sign is seen in which of the following conditions?
- A. NCC
- B. Spina bifida (Correct Answer)
- C. Omphalocele
- D. Anencephaly
Explanation: ***Spina bifida*** - The **"banana sign"** is a distinctive ultrasound finding associated with **Chiari II malformation**, which is frequently seen in cases of **spina bifida**. - It refers to the characteristic **flattening and anterior bowing of the cerebellar hemispheres**, compressing them against the skull and giving them a banana-like appearance. *NCC* - **Neurocysticercosis (NCC)** is caused by tapeworm larvae in the central nervous system and is characterized by **cysts** or calcifications on imaging, not a "banana sign." - Imaging findings in NCC typically include **cystic lesions**, **edema**, and calcifications, unrelated to cerebellar shape. *Omphalocele* - **Omphalocele** is an abdominal wall defect where abdominal organs protrude through the navel, covered by a membrane. - The ultrasound findings for omphalocele involve visualization of abdominal contents outside the abdominal cavity, which is distinct from intracranial findings like the "banana sign." *Anencephaly* - **Anencephaly** is a severe birth defect where a baby is born without parts of the brain and skull, typically presenting with an **absent cranial vault** and cerebral hemispheres. - While a severe neural tube defect, anencephaly features agenesis of the brain and skull, rather than the cerebellar distortion seen as a "banana sign."
Question 9: On Doppler, the most ominous sign indicating fetal compromise is:
- A. ↑ pulsatility index in umbilical artery
- B. ↑ S/D blood flow ratio
- C. ↑ Cerebral artery flow
- D. Absent diastolic flow (Correct Answer)
Explanation: ***Absent diastolic flow*** - This indicates a severe increase in **vascular resistance** within the placental circulation, signifying significant fetal compromise. - The absence of forward flow during diastole means the fetus is receiving **minimal blood supply** during relaxation, leading to hypoxia and acidosis. *↑ pulsatility index in umbilical artery* - An elevated pulsatility index (PI) suggests increased resistance to blood flow in the **placental circulation**, indicating compromise. - However, it is generally less severe than absent or reversed diastolic flow, which are later stages of fetal compromise. *↑ S/D blood flow ratio* - An increased S/D ratio in the umbilical artery signifies **higher resistance** to blood flow, often due to placental insufficiency. - While concerning, it is considered an earlier indicator of compromise compared to the complete absence of diastolic flow. *↑ Cerebral artery flow* - Increased cerebral artery flow (often decreased PI in the middle cerebral artery) is a sign of **brain-sparing effect**, where the fetus redistributes blood flow to essential organs. - This is a compensatory mechanism and, while indicating compromise, means the fetus is still able to adapt to some extent, unlike absent diastolic flow which represents decompensation.
Question 10: 18 weeks pregnant female presents with no high risk of NTD and low risk of trisomy 21 on quad test. What is the most appropriate next step in management?
- A. Repeat non-invasive screening test.
- B. Perform invasive diagnostic testing.
- C. Perform amniotic fluid analysis.
- D. Perform a detailed fetal ultrasound. (Correct Answer)
Explanation: ***Perform a detailed fetal ultrasound.*** - A **detailed fetal ultrasound** (often referred to as an **anatomy scan**) at around 18-22 weeks is a standard component of prenatal care for all pregnant women, regardless of screening test results. - This ultrasound evaluates fetal anatomy for structural anomalies, assesses fetal growth, and confirms gestational age, providing crucial information even with low-risk screening. *Repeat non-invasive screening test.* - Repeating a non-invasive screening test (like another quad screen or NIPT) is generally **not indicated** when initial results show a low risk and there are no other clinical concerns. - Such tests are primarily for screening purposes, and a second low-risk result would offer little additional actionable information, as their positive predictive value is low. *Perform invasive diagnostic testing.* - **Invasive diagnostic testing**, such as **amniocentesis** or **chorionic villus sampling (CVS)**, carries a risk of miscarriage and is reserved for situations with a high risk of chromosomal abnormalities or genetic conditions. - Given the low-risk quad screen results for trisomy 21 and no high risk for NTDs, invasive testing is **not warranted** at this stage. *Perform amniotic fluid analysis.* - **Amniotic fluid analysis** is part of an amniocentesis, an **invasive diagnostic procedure** designed to detect chromosomal abnormalities or genetic disorders. - This procedure is typically reserved for cases where screening tests indicate a high risk or there is a clinical suspicion of a genetic condition; it's **not a routine step** after a low-risk quad screen.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free