Obstetrics 10

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prem.sigdel7
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Obstetrics 10
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2015-08-15 09:26:44
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Isoimmunization PROM preterm labor tocolytics Chorioamnitis
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Obstetrics
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  1. What is Erythroblastosis fetalis?
    • Erythroblastosis fetalis  is hemolytic anemia in the fetus caused by transplacental transmission of maternal antibodies to fetal RBCs. It can be 
    • - Rh Incompatibility
    • - ABO Incompatibility
  2. What should be the Rh status of mother and fetus for Rh incompatibility? [SGPGI 03]
    • It occurs only in some second or subsequent pregnancies of Rh negative women  carries an Rh positive fetus.  [IOM 11]
    • At the time of delivery, fetal red blood cells may enter maternal circulation, stimulating antibody production against the Rh factor.
    • In a subsequent pregnancy, these antibodies cross the placenta to the fetal circulation and destory fetal RBC.
  3. ABO hemolytic disease of newborn occurs when the blood group of mother is 
    A) A
    B) AB
    C) O
    D) B
    C) O

    Blood group involved in ABO incompatibility is O of mOther and A, B, AB of bABy. 
    The mother with blood group O has got naturally occurring anti-A and anti-B antibodies. These antibodies are mainly IgM types and do not cross the placenta.
    If the fetus happens to be blood group  A or B corresponding to that of father, the immune antibodies are formed in response to the entry of A or B antigen bearing fetal red cells, into the maternal circulation.  As these are mainly IgG, they can cross the placenta into the fetal circulation and cause a  variable amount  of hemolysis due to antigen-antibody reaction.
    (this multiple choice question has been scrambled)
  4. What is isoimmunization?
    • Active immunization of an individual against blood from an individual of the same species, esp. the production of anti-Rh antibodies by Rh-negative mothers against red fetal blood cell antigens.
    • During maternal trauma, loss of pregnancy (abortion), or delivery, some of the infant’s blood is transferred to the mother, stimulating antibody production.
    • If a second child is Rh-positive, the mother’s anti-Rh antibodies will cross the placenta and cause hemolytic disease of the newborn.
  5. What is the screening test we  use to detect the isoimmunization?
    Atypical antibody test  (AAT) – or indirect coombs test
  6. What are the risk factors for Isoimmunization? 
    • Amniocentesis 
    • Ectopic pregnancy
    • Dilatation and Curettage 
    • Abruptio placenta 
    • Placenta previa 
  7. What are the antigens  that causes hemolytic disease?  Which causes mild and which causes severe hemolysis?
    • CDE  antigens  - severe hemolysis
    • Kell antigens -  severe hemolysis
    • Kidd  antigens - severe hemolysis
    • Duffy antigens - severe hemolysis
    • Diego antigens -  severe hemolysis
    • Lutheran antigens  -  mild hemolysis
    • Lewis antigens  -  mild hemolysis
    • [ @ kell, kidd – kills, duffy, diego - dies, Lutheran, Lewis – Lives]


    Although more than 400 blood groups have been identified, the ABO blood group system remains the most important in clinical medicine because ABO(H) antibodies are invariably present in plasma when person RBC lacks the corresponding antigen. [AIIMS 02,03]
  8. Blood  group antigen is present in which of the following [UP 98]
    a) Pulp of tooth 
    b) Saliva 
    c) Vaginal fluid 
    d) All of the above
    d) All of the above

    • In ABO blood group antigen system, H substance is the immediate precursor of A and B antigens.
    • H substance + N-acetylgalactosamine = A antigen
    • H substance + galactose = B antigen.

    A,B and H antigens are not confined to erythrocytes, but can be detected in almost all the tissues and fluids of the body such as saliva, gastric juice and sweat secretions.  [UP 98]
  9. What  is the most common RBC antigen that is involved in Isoimmunization?
    • Big D.
    • Other antigens in  CDE system are c, C, e, E  but there is no ‘d’ – small d antigen.
  10. What should  be the titre of the antibodies  in maternal blood  to cause the hemolytic disease of newborn? 
    >1:8 
  11. How  can you find if the fetus is anemic or not?
    Amniocentesis for Amniotic fluid (AF) bilirubin – we assume that if the  higher the bilirubin level, the lower the  Hb level.

     

    Perrcutaneous Umbilical cord blood sampling – for fetal Hct

    Ultrasound middle cerebral artery peak systolic velocity
  12. What  is the  most common management  if fetal hematocrit is ≥25%?
    • Repeat PUBS if <34 weeks=no  transfusion required
    • Delivery if ≥ 34 weeks.
    • [transfusion is to be done if Hct ≤25%]
  13. What happens  to middle cerebral artery peak systolic velocity as anemia increases?
    • Peak systolic velocity increases as anemia increases. 
  14. What are the indications of intrauterine transfusion?
    Amniotic Fluid Optical density 450 in Zone III in liley graph, <34 weeks POG [AIIMS 04,05] 

    Fetal Hct is < 25%, <34 weeks

    MCA peak velocity is high. i.e in zone D, <34 wks
  15. What is the MOA  of RhoGAM?
    It is a passive anti-D IgG antibody, that lyses D+ RBC before lymphocytes are activated.
  16. When do you give RhoGAM?
    At 28 weeks, and after delivery if baby is Rh+. 

    We should give extra dose of RhoGAM after CVS(chorionic villous sampling), amniocentesis, D & C, Ectopic pregnancy, Abruption and placenta previa.
  17. What  is the dose of RhoGAM that neutralizes 15 ml of RBC?
    300μg RhoGAM (1 vial)  neutralize 15 ml of RBC.
  18. Define PROM?
    • It is premature rupture  of membrane. Rupture of membrane before onset of labor [AI 97], may be previable, preterm and term.
    • The main factor is  contraction has not begun.
  19. What are the risk factors of PROM?
    1. Ascending Infection (previously, it was thought that rupture occurs first then infection. Now it is understood that first infection occurs, makes the membrane weak and then rupture) 

    2. Membrane defects 

    3. Smoking
  20. A women presents with leakage of fluid per vaginum and meconium stained liquor at 34 weeks of gestation. The most likely organism causing infection would be [AI 10]
    A) Herpes
    B) CMV 
    C) Toxoplasmosis
    D) Listeria monocytogenes 
    D) Listeria monocytogenes

    Leakage of fluid per vaginum at 34 weeks gestation suggests a diagnosis of Preterm premature rupture of membrane. Most causes of PPROM are attributed to Bacterial Infections (Group B streptococci, Gardernella) and Listeria Monocytogenes.
    (this multiple choice question has been scrambled)
  21. How do you diagnose  PROM?
    By speculum examination, pooling of amniotic fluid in posterior fornix. 

    Nitrazine paper (pH paper)[JIPMER 00]  turns dark  as the fluid is alkaline 




    • Ferning pattern of amniotic fluid  because of presence of sodium chloride crystals
  22. What is the normal pH of vaginal secretion and amniotic fluid?
    • Vaginal secretion -  4.5-5.5
    • Amniotic fluid - 7.0-7.5  [AIIMS 01] - nitrazine paper turns dark as the amniotic fluid is alkaline.
  23. How do you diagnose Chorioamnionitis?
    • Clinical diagnosis is  made with all of the following:
    • - Maternal fever 
    • - Uterine tenderness 
    • - Confirmed PROM
    • - Purulent or foul-smelling amniotic fluid or vaginal discharge [IOM 04] 
    • - Absence of URI,RTI or UTI
  24. What is the management of PROM?
    • If uncomplicated - 
    • < 24 weeks - Before viability - there is pulmonary hypoplasia - Either induce labor or Send home for bed rest.  Tell her come back if she has fever  or contractions have started. 
    • 24-35 weeks - Preterm viable – there is problem with prematurity - Hospitalize, maternal sterioids, Cervical cultures, 7 days of ampicillin and Erythromycin 
    • >36 weeks - Delivery   

    • If Chorioamnitis - Give Genta/Clinda, Oxytocin, deliver
    • If fetus  compromised - deliver
  25. How do you differentiate Uterine irritability, Braxton Hicks contractions, Preterm contractions and preterm labor?
    Uterine irritability - low intensity, high frequency contractions

    Braxton Hicks contraction - low intensity, low frequency contractions, starts as soon as 14 weeks.

    Preterm contractions -  pregnancy 20-36 weeks,  3 contractions in 30  minutes, <2 cm or no change in  cervix, no need to treat.

    Preterm  labor - pregnancy 20-36 weeks,  3 contractions in 30  minutes, dilated  2 cm or changing cervix

  26. What is the clinical diagnosis for Preterm labor?
    • Gestational age 20weeks and <36 wks, Contractions 3 in 30 minutes
    • Cervix change in dilation/effacement in serial exams or 2cm on 1 exam.

    [Note: We take 2 cm because many multipara are 1-2 cm dilated  for more than a week.]
  27. What are the  risk factor for preterm birth?
    • Multiple gestation [IOM 00] 
    • Uterine anomaly 
    • Previous preterm birth
    • Infections
  28. On Transvaginal Sonography, which of the following shapes of cervix indicate the imminent preterm labor? [AI 07]
    A) T
    B) O
    C) Y
    D) U 
    D) U

    Cervical effacement begins with the dilatation of the internal OS and is visualized in USG as the amniotic sac protrudes into the cervical canal.
    The letters T, Y, V and U illustrate the corelation between the length of the cervix and changes of the internal cervical OS graphically.
    The process of complete effacement may be described as U shaped or V shaped depending on the descent of fetal head.

    (this multiple choice question has been scrambled)
  29. What is Nile blue sulphate stain?
    • It is the stain used for maturity  assessment of amniotic fluid cells. 
    • When 10% of cells from amniocentesis sample of fluid stain orange, then pregnancy has reached at least 38 weeks and it has reached term or beyond when 50% react in this way.
  30. What are the contraindications to tocolytics  in preterm labor?
    • A. Obstetric:
    • - severe abruptio,
    • - ruptured membranes,
    • - chorioamnionitis
    • B. Fetal:
    • - lethal anomaly,
    • - fetal demise,
    • - fetal jeopardy
    • C. Maternal:
    • - eclampsia,
    • - severe preeclampsia,
    • - advanced dilatation

    90% cases  have one or more of these contraindications.
  31. Name the tocolytics that can be used in preterm labor? [IOM 10,AI 08]
    • MgSO4 [AI 99] 
    • β-adrenergic agonists- Ritodrine [AIIMS 97, KERELA 99],Terbutiline, Isoxsuprine
    • CCB – Nifedipine 
    • Cycloxygenase inhibitors – Indomethacin, Atosiban [AIIMS 03]
  32. What are the major side effects of  β-adrenergic agonists?
    • Hypotension
    • Tachycardia
    • Hyperglycemia 
    • Hypokalemia

    [Note: This medication may require insulin in GDM]
  33. What are the  side effects of  PG synthetase  inhibitors?
    • Oligohydraminos - due to decreased renal perfusion resulting in decreased amniotic fluid
    • Intrauterine closure of PDA
  34. What is the duration of use of tocolytics?
    We can use tocolytics for delaying the delivery for 48 hrs to buy time to use the  Betamethasone to increase the production of surfactants.
  35. What are the indications and timing of antenatal steroids?
    • Indications:
    • - To reduce incidence of Respiratory Distress Syndrome [AI 07] 
    • - To reduce incidence of intraventricular hemorrhage

    • Timing:
    • - Pregnancy <34 weeks
    • - Administration is beneficial when delivery is delayed beyond 48 hours of first dose. 


    Betamethasone or Dexamethasone can be used. But, Betamethasone is the steroid of choice.

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