<prompt> The immunoglobulin that crosses placental barrier isIgMIgGIgAIgD  <response>: Ans. b IgG. Ref: Jawetzs Medical Microbiology, 24thTable 8-l;Obstetrics by Dutta, 4th677 Antigens of MCH have been shown to be well expressed in newborn, in the fetus and in embryo of 10th week. IgG abs can cross placenta. IgGIgAIgMIgEIgDHeavy chain symbolgabedMolecular weight x 1000150170 or 4001900190150Serum concentration mgmL7-180.8-40.4-2.5 0.0005 0.003Serum half-life days217722Activates complementYes NoYes NoNoPercentage of total immunoglobulins in serum80136 1 1Crosses placentaYesNoNoNono 