Obstetrics 10

• 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

• 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.

D) 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.

• 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.

Atypical antibody test  (AAT) – or indirect coombs test

• Amniocentesis 
• Ectopic pregnancy
• Dilatation and Curettage 
• Abruptio placenta 
• Placenta previa 

• 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]

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]

• Big D.
• Other antigens in  CDE system are c, C, e, E  but there is no ‘d’ – small d antigen.

>1:8 

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

• Repeat PUBS if <34 weeks=no  transfusion required
• Delivery if ≥ 34 weeks.
• [transfusion is to be done if Hct ≤25%]

• Peak systolic velocity increases as anemia increases. 

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

It is a passive anti-D IgG antibody, that lyses D+ RBC before lymphocytes are activated.

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.

300μg RhoGAM (1 vial)  neutralize 15 ml of RBC.

• 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.

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

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.

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

• Vaginal secretion -  4.5-5.5
• Amniotic fluid - 7.0-7.5  [AIIMS 01] - nitrazine paper turns dark as the amniotic fluid is alkaline.

• 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

• 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

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

• 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.]

• Multiple gestation [IOM 00] 
• Uterine anomaly 
• Previous preterm birth
• Infections

C) 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.

• 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.

• 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.

• MgSO₄ [AI 99] 
• β-adrenergic agonists- Ritodrine [AIIMS 97, KERELA 99],Terbutiline, Isoxsuprine
• CCB – Nifedipine 
• Cycloxygenase inhibitors – Indomethacin, Atosiban [AIIMS 03]

• Hypotension
• Tachycardia
• Hyperglycemia 
• Hypokalemia

[Note: This medication may require insulin in GDM]

• Oligohydraminos - due to decreased renal perfusion resulting in decreased amniotic fluid
• Intrauterine closure of PDA

We can use tocolytics for delaying the delivery for 48 hrs to buy time to use the  Betamethasone to increase the production of surfactants.

• 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.