Obstetrics Marrow Pg 325-334 (Normal Pregnancy & ANC)
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Questions and Answers

What is the suspected diagnosis if the gestational sac is ≥10mm and no yolk sac is visible?

  • Normal pregnancy
  • Missed abortion
  • Anembryonic pregnancy
  • Ectopic pregnancy (correct)

    • Cardiac activity can be observed via m-mode at 6 weeks of gestation.

    True

    What is the cutoff value for mean sac diameter (MSD) to measure crown rump length (CRL) or visualize the fetal pole?

    ≥25mm

    At 6 weeks of gestation, the fetal heart rate (FHR) ranges from _____ bpm.

    <p>110–130</p> Signup and view all the answers

    Match the following criteria to their respective outcomes:

    <p>&lt; 25mm MSD = Repeat USG in 1 week ≥ 25mm MSD with no fetal pole = Missed abortion: a blighted ovum CRL cannot be measured = Medical abortion recommended Fetal pole seen = Normal development expected</p> Signup and view all the answers

    What does the double decidual sac sign indicate?

    <p>Intrauterine pregnancy</p> Signup and view all the answers

    The crown rump length is considered the best parameter to estimate gestational age in the second trimester.

    <p>False</p> Signup and view all the answers

    What is the first ultrasound sign of early pregnancy?

    <p>Intradecidual sign</p> Signup and view all the answers

    The _____ sign consists of one bleb for the yolk sac and another for the amniotic sac.

    <p>double bleb</p> Signup and view all the answers

    Match the trimester with its best parameter for estimating gestational age:

    <p>Trimester 1 = Crown rump length Trimester 2 = Biparietal diameter Trimester 3 = Combination of parameters</p> Signup and view all the answers

    What is the formula to estimate gestational age using the Mean Sac Diameter (MSD)?

    <p>MSD (in mm) + 30</p> Signup and view all the answers

    Crown Rump Length (CRL) is used for estimating gestational age until 13 weeks + 6 days and can be used when CRL is greater than or equal to 84mm.

    <p>False</p> Signup and view all the answers

    What is the minimum CRL measured on ultrasound for estimating gestational age?

    <p>5mm</p> Signup and view all the answers

    The biparietal diameter is measured in the _______ plane.

    <p>transthalamic</p> Signup and view all the answers

    Match the ultrasound recommendation with its indicated week range:

    <p>Viability scan = 6 - 8 weeks Nuchal translucency scan = 11 - 13 weeks + 6 days Target/anomaly scan = 18 - 22 weeks Growth scan = 32 - 34 weeks</p> Signup and view all the answers

    What is the best time frame for performing a TIFFA ultrasound to detect congenital malformations?

    <p>18-22 weeks</p> Signup and view all the answers

    Routine ultrasound (Level 1) is used primarily for detecting chromosomal anomalies.

    <p>False</p> Signup and view all the answers

    Name a condition that results from the failure of the cranial neuropore to close.

    <p>Anencephaly</p> Signup and view all the answers

    A condition where brain tissue herniates out through a defect in the skull is called an __________.

    <p>encephalocele</p> Signup and view all the answers

    Match the following types of cranial defects to their descriptions:

    <p>Acrania = Absence of skull, meninges, and muscle Small defect = Meninges and brain tissue herniate out, covered with meninges and scalp Encephalocele = Brain tissue herniates out; most common site is the occipital bone Anencephaly = Destruction and degeneration of brain tissue occurs</p> Signup and view all the answers

    Which condition typically shows a cauliflower-like appearance on ultrasound?

    <p>Gastroschisis</p> Signup and view all the answers

    Karyotyping is required for the diagnosis of gastroschisis.

    <p>False</p> Signup and view all the answers

    At what gestational age is maximum alpha-feto protein level found in fetal serum?

    <p>13 weeks</p> Signup and view all the answers

    Elevated alpha-feto protein levels in the fetus are associated with __________ defects.

    <p>neural tube</p> Signup and view all the answers

    Match the following fetal conditions with their associated alpha-feto protein levels:

    <p>Neural tube defects = Increased Gestational trophoblastic disease = Decreased Omphalocoele = Increased Trisomy 21 = Decreased</p> Signup and view all the answers

    What is the term used for the absence of the skull in anencephaly?

    <p>Acrania</p> Signup and view all the answers

    Anencephaly is a viable condition.

    <p>False</p> Signup and view all the answers

    What is the recommended daily dose of folic acid supplementation to prevent recurrence of neural tube defects (NTD)?

    <p>4mg/day</p> Signup and view all the answers

    The _____ sign on ultrasound is associated with the irregular contour of the fetal head in anencephaly.

    <p>shower cap</p> Signup and view all the answers

    Match the ultrasound signs with their descriptions:

    <p>Shower cap sign = Irregular contour of fetal head Mickey mouse sign = Triangular face Frog eye sign = Large bulging eyes / deep eye sockets Polyhydramnios = Excessive amniotic fluid</p> Signup and view all the answers

    Which of the following conditions is associated with caudal defects of the neural tube?

    <p>Spina bifida occulta</p> Signup and view all the answers

    The best biochemical marker for detecting neural tube defects is alpha-fetoprotein (AFP).

    <p>False</p> Signup and view all the answers

    What is the typical prevalence of caudal defects in births?

    <p>1 in 2000</p> Signup and view all the answers

    The _____ sign on ultrasound indicates downward displacement of the cerebellum.

    <p>banana</p> Signup and view all the answers

    Match the types of spina bifida with their descriptions:

    <p>Spina bifida occulta = No herniation of meninges and spinal cord Meningocele = Herniation of meninges but no spinal cord involvement Meningomyelocele = Herniation of both meninges and spinal cord</p> Signup and view all the answers

    At what gestational age is the best time to localize the placenta using ultrasound?

    <p>32 weeks</p> Signup and view all the answers

    Short femur measurements can indicate constitutional delay or Down syndrome.

    <p>True</p> Signup and view all the answers

    What is the purpose of performing serial ultrasounds in a suboptimally dated pregnancy?

    <p>Estimate gestational age and rule out IUGR</p> Signup and view all the answers

    Fetal echo is typically performed between ______ and ______ weeks.

    <p>22, 24</p> Signup and view all the answers

    Match the following conditions with their associated risks:

    <p>Lithium therapy = Ebstein anomaly Maternal rubella infection = Patent ductus arteriosus Gestational diabetes = Ventricular septal defect (VSD) Phenylketonuria = Microcephaly and CNS abnormalities</p> Signup and view all the answers

    What is an indication for performing a fetal echo?

    <p>Fetal heart rate arrhythmia</p> Signup and view all the answers

    A single ultrasound before 22 weeks is sufficient for dating a pregnancy.

    <p>False</p> Signup and view all the answers

    What condition is associated with a severely short femur measurement?

    <p>Skeletal dysplasia or early-onset IUGR</p> Signup and view all the answers

    What is the key characteristic that differentiates gastroschisis from omphalocoele?

    <p>Gastroschisis involves herniation of abdominal contents not enclosed in a sac.</p> Signup and view all the answers

    Chiari 3 malformation involves the herniation of the cerebellum and meninges through a cranial defect.

    <p>True</p> Signup and view all the answers

    What is the medical term for the condition where both brain and meninges herniate through a cranial defect?

    <p>Encephalocele</p> Signup and view all the answers

    The _____ sign on an ultrasound indicates a specific abnormality related to the fetal brain.

    <p>Lemon</p> Signup and view all the answers

    Match the following conditions with their descriptions:

    <p>Craniorachischisis = Defect in both skull and spine Omphalocoele = Herniation of abdominal contents in a sac Gastroschisis = Herniation of abdominal contents without a sac Chiari 3 malformation = Herniation of cerebellum and other structures</p> Signup and view all the answers

    What is the cut-off value for crown rump length (CRL) to visualize cardiac activity?

    <p>7mm</p> Signup and view all the answers

    A pseudo gestational sac is characterized by the presence of a yolk sac.

    <p>False</p> Signup and view all the answers

    What does an increase in β hCG but not doubling suggest about the pregnancy?

    <p>Ectopic pregnancy</p> Signup and view all the answers

    The minimum β hCG value at which the gestational sac is visible on transvaginal ultrasound (TVS) is _____ IU/L.

    <p>1000</p> Signup and view all the answers

    Match the following conditions with their respective criteria:

    <p>True gestational sac = Eccentric Location, Present Yolk sac Pseudo gestational sac = Central Location, Absent Yolk sac Ectopic pregnancy = β hCG ≥ 2000 IU/L, gestational sac not seen Missed abortion = CRL ≥ 7mm, Cardiac activity absent</p> Signup and view all the answers

    Which of the following indicates a missed abortion?

    <p>CRL ≥ 7mm with cardiac activity absent</p> Signup and view all the answers

    The presence of double bleb sign indicates a true gestational sac.

    <p>True</p> Signup and view all the answers

    What is the critical titer for β hCG to visualize a gestational sac via transabdominal ultrasound (TAS)?

    <p>6500 IU/L</p> Signup and view all the answers

    Study Notes

    Ultrasound In Pregnancy Part 1

    • Missed Abortion: If gestational sac is ≥ 25mm and no fetal pole/CRL can be measured then it can be concluded as missed abortion.
    • CRL measurement: In twin pregnancies, if there is a discrepancy in CRL measurements, the EDD is calculated based on the larger twin.
    • Biparietal Diameter (BPD): Measured in the transthalamic plane (from the outer table on one side to the inner table on the opposite side).
    • Ultrasound Indications:
      • Done to rule out ectopic pregnancy when a patient experiences abdominal pain.
      • Done to determine viability when a patient has bleeding in the first trimester.
      • Done to determine if the size of the uterus matches the length of gestation
      • Done when a patient is unsure about their LMP.
    • USG Recommendations:
      • 6-8 weeks: Viability scan.
      • 18-22 weeks: Target/anomaly/booking scan (TIFFA).
      • 11-13 weeks + 6 days: Nuchal translucency scan.
      • 32-34 weeks: Growth scan.

    Early Pregnancy on USG

    • Intradecidual Sign: This is the first sign observed when a gestational sac is present, indicating the implantation of the blastocyst in the endometrium.
    • Double Decidual Sac/Double Ring Sign: This is the second sign observed where the inner ring represents the decidua capsularis and outer ring the decidua parietalis.
    • Double Bleb Sign: The third sign is the presence of two blebs. One bleb represents the yolk sac and the other bleb represents the amniotic sac.
    • Gestational Age Estimation: The accuracy of gestational age relies on the time of ultrasound. The earlier the ultrasound, the more precise the gestational age estimation.
    • Estimating Gestational Age:
      • Trimester 1: Crown rump length (CRL) is the best parameter to estimate gestational age.
      • Trimester 2: BPD (biparietal diameter) is the best parameter.
      • Trimester 3: A combination of parameters, with femur length being the best single parameter, are used to estimate gestational age.

    Ultrasound In Pregnancy Part 2

    • Level 2 USG (TIFFA): Best performed between 18-22 weeks. It detects gross congenital anomalies in the fetus and chromosomal anomalies need to be assessed with karyotyping.
    • Level 1 USG: Useful for detecting some common congenital malformations like neural tube defects (NTDs).
    • Neural Tube Defect (NTD): Occurs when there is a problem with the closure of the neuropore, or fusion of the neural tube.

    Cranial Defect

    • Acrania: Absence of skull, meninges, and muscles.
    • Encephalocele: Herniation of brain tissue covered by meninges and scalp, mostly through the occipital bone.
    • Anencephaly: Severe NTD where brain tissue degenerates and is destroyed.

    Omphalocoele

    • On USG: Appears with a smooth outline.
    • Site: Located at the umbilicus.
    • Associated with: Trisomy 18 > Trisomy 21.
    • Karyotyping: Required.

    Gastroschisis

    • On USG: Appears with a cauliflower-like appearance.
    • Site: Located to the left or right of the umbilicus.
    • Karyotyping: Not required.

    Alpha-Fetoprotein (AFP)

    • Salient features: Fetal-specific globulin produced by the yolk sac, fetal GIT, and liver.
    • Maximum level in fetal serum: At 13 weeks of pregnancy.
    • Maternal serum AFP: Ideally tested between 16-18 weeks, but earliest detection can be done by 15 weeks.

    Fetal conditions associated with raised AFP levels:

    • Neural tube defects (NTD)
    • Abdominal wall defect
    • Pilonidal sinus
    • Fetal death

    Fetal conditions associated with decreased AFP levels (Mnemonic: Diabetic GOAT):

    • Maternal Diabetes
    • Gestational Trophoblastic Disease
    • Overestimated Gestational Age
    • Abortion
    • Trisomy of fetus

    Normal Pregnancy and Antenatal Care

    • CRL cutoff to see cardiac activity: ≥ 7mm (Cardiac activity present), <7mm (Cardiac activity absent).
    • Missed Abortion on USG:
      • Specific criteria: - If MSD ≥ 25mm and fetal pole not seen/CRL cannot be measured. - If CRL ≥ 7mm and cardiac activity absent. - If ≥ 14 days have passed after the first scan showing gestational sac: yolk sac/cardiac activity absent. - If ≥ 11 days passed after the first scan showing gestational sac + yolk sac: cardiac activity absent.
      • β hCG:
        • Cut-off value to visualize gestational sac (Critical titer): 2000 IU/L for TVS and 6500 IU/L for TAS.
        • If β hCG value ≥2000 IU/L and the gestational sac is not seen, then it is an ectopic pregnancy.
        • Minimum β hCG value at which a gestational sac is visible on TVS: 1000 IU/L.
        • β hCG repeat value (After 48hrs): - Doubled: Live intrauterine pregnancy. - Increased but not doubled: Ectopic pregnancy. - Decreased: Dying intrauterine pregnancy (Abortion).

    Anencephaly

    • Salient features:

      • Missing skull (Acrania)
      • Absent or hypoplastic adrenal and pituitary gland
      • Increased risk of post-term pregnancy
      • Decreased fetal DHEAS and estrogen levels
      • Associated swallowing defect (Polyhydramnios)
      • Fetal presentation: Face (Face of the fetus is normal)
      • Non-viable condition

    • On USG:

      • First congenital anomaly to be recognized on USG, with the earliest detection at 10 weeks and best detection at 14 weeks.
      • Shower cap sign (irregular contour of the fetal head)
      • Mickey mouse sign (triangular face)
      • Frog eye sign (large bulging eyes/deep eye sockets)
      • Polyhydramnios (In the T2 or late 2nd trimester)

    Management

    • MTP: Irrespective of gestational age after a medical board decision.

    Recurrent risk of NTD:

    • 5% after one NTD
    • 10% after two NTD

    Prevention of NTD:

    • Folic acid supplementation:
      • Dose: 400mcg/day
      • Dose to prevent recurrence: 4mg/day

    Note:

    • Hyperthermia/fever in the first trimester (temperature ↑ by ≥ 1.5°C) can cause teratogenic effects.
    • NTD, microcephaly, learning disability, and seizures.

    Diagnosis of NTD:

    • Screening test:
      • Current Level I USG
      • Earlier maternal serum AFP levels (15-20 weeks)
    • Diagnostic test:
      • Level 2 USG/TIFFA
      • Amniocentesis (AFP and acetylcholinesterase levels)

    Caudal Defect of Neural Tube

    • Prevalence: 1 in 2000 births
    • Caudal Defects: Non-closure of vertebral arches
      • Spina bifida occulta: No herniation of meninges and spinal cord
      • Meningocele: Herniation of meninges and no herniation of spinal cord.
      • Meningomyelocele: Herniation of meninges and spinal cord.
    • On USG:
      • Banana sign: Downward displacement of the cerebellum.
      • Lemon sign: Bossing of the frontal bone.
      • Associated ventriculomegaly.
      • Polyhydramnios.
      • These signs are also seen in Arnold Chiari malformation/Chiari II malformation

    Craniorachischisis: Cranial + Caudal Neural Tube Defect.

    • Note:
      • Cephalocele: Herniation of meninges through a cranial defect.
      • Encephalocele: Herniation of brain and meninges through a cranial defect.
      • Chiari 3 Malformation: Encephalocele with herniation of cerebellum and other posterior fossa structures.

    Abdominal Wall Defect

    • Omphalocoele: Herniation of abdominal contents that is enclosed in a sac.
    • Gastroschisis: Herniation of abdominal content that is not enclosed in a sac.

    Ultrasound In Pregnancy Part 1

    • Uses of USG:*
    • Cervical Length Measurement (in preterm labor): For all pregnant women with a history of preterm labor, a transvaginal ultrasound (TVS) should be performed between 16 and 24 weeks to measure cervical length.
    • Placental Localization: Best performed at 32 and 36 weeks gestation.
    • Chorionicity in Twins: Measured between 10 and 14 weeks.
    • Short Femur Indicates:*
    • Constitutional delay
    • Down syndrome
    • Severely Short Femur Indicates:*
    • Skeletal dysplasia
    • Early-onset IUGR
    • Suboptimally Dated Pregnancy:*
    • No USG before 22 weeks
    • Single USG is not useful
    • Serial USG (3-4 weeks apart) is useful to:
      • Estimate gestational age
      • Rule out Intrauterine Growth Restriction (IUGR)
    • Fetal Echo:*
    • Not routinely performed unless there is suspicion of fetal cardiac disease.
    • Performed between 22 and 24 weeks.
    • Indications for Fetal Echo:*
    • Fetal heart rate (FHR) arrhythmia
    • Maternal rubella infection (increased risk of patent ductus arteriosus)
    • Fetal aneuploidy (e.g., Down syndrome, endocardial cushion defect)
    • Nuchal translucency (NT) ≥ 3mm
    • Monochorionic twin (TTTS): Increased risk of heart failure (HF) in the recipient twin
    • Other Factors:*
    • Lithium therapy: Ebstein anomaly
    • History of fetus with heart block in the setting of maternal anti-Ro/La antibodies (SLE): Increased risk of VSD
    • Gestational diabetes: Increased risk of VSD
    • Phenylketonuria: Increased risk of microcephaly and central nervous system (CNS) abnormalities.

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    Description

    This quiz covers essential concepts related to prenatal ultrasound, including methods for assessing missed abortion, measuring crown-rump length (CRL) in twin pregnancies, and understanding various ultrasound indications and recommendations. It is a valuable resource for students and practitioners in obstetrics and gynecology, providing foundational knowledge for interpreting ultrasound results during pregnancy.

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