A 28 years old female at term presents with gush of fluid and regular contractions. Prenatal investigations reveals Rh negative, antibody negative, husband- Rh positive homozygous. After 10 hours her labor progresses and delivered 3600g baby via normal vaginal delivery. Placenta did not separate spontaneously and manual removal was done. The next step of investigation is
Answer: c) Direct Coomb's testRh NEGATIVE PREGNANCYINVESTIGATION OF Rh NEGATIVE MOTHERSI-Husband's blood grouping & Rh typing.II-Obstetric History: If the woman is primi, it is unlikely for the baby to be affectedIII-Antibody detection: In all cases of Rh negativity, albumin antibody is detected by indirect Coomb's test at 12th week to detect unbound antibodies in maternal serum.If the test is found negative, it is to be repeated at 28th and 36th week in primi & at monthly intervals from 24th week onwards in multi.If the test is found positive:Genotype of the husband should be determined If he is found to be homozygous, the fetus is likely to be affected & in heterozygous, the fetus may be affected in 50% cases.Quantitative estimation of the albumin antibody at weekly intervals. A titre of 1:16 or antibody level >10 lU/ml is critical.Fetal Rh status & blood grouping is done by amniocentesis.Amniocentesis is done & bilirubin in the amniotic fluid is estimated by spectrophotometer at 250-700nm wave length.In presence of bilirubin, there is a "deviation bulge" at 450nm wave length.This deviation is plotted in a Liley's chart.ANTI-D ADMINISTRATIONCalculation of the dose: Approximate volume of fetal blood entering into the maternal circulation is estimated by Kleihauer-Betke test/ rosette. (Calculating the RBC's under 50 low power fields).80 fetal RBCs correspond to 4 ml of fetal bloodDosage: 10mg for every 1 ml of fetal whole bloodTime of administration & Dosage:It should be given when the baby born is Rh positive and the direct Coombs test is negative.Should be given preferably within 72 hours or earlier following delivery or abortion.First trimester- abortion, ectopic pregnancy, chorion villous biopsy: 50 mg l.m.Beyond twelve weeks & Following delivery: 300mg l.m.In case of Rh iso immunization:Cord should be kept long (2-4cms) to enable exchange transfusion if requiredCord blood sample should be taken from the placental end for:ABO and Rh groupingDirect Coomb's testMeasurement of serum bilirubinHemoglobin estimationBlood smear for presence of immature RBC's.
RhoGAM
Indirect Coomb's test
Direct Coomb's test
Detection of fetal cells in maternal circulation
Miscellaneous (Gynae)