1. 75 to 80% of Complete molar pregnancies usually arise as a consequence of duplication of a single sperm following
fertilisation of an ‘empty’ ovum. Some complete moles (20–25%) can arise after dispermic fertilisation of an ‘empty’
ovum.
2. Partial molar pregnancies are usually (90%) triploid in origin, with two sets of paternal haploid chromosomes and one set of maternal haploid chromosomes.
Occasionally molar pregnancies are tetraploid or mosaic conceptions. ( Remember- All triploid or tetraploid pregnancies are not partial molar pregnancies. Diagnosis of partial mole requires histopathological evidence of trophoblastic hyperplasia)

3. Complete molar pregnancies do not have Red Blood Cells. Poor vascularisation of the chorionic villi and absence of the D antigen by trophoblast cells means that anti-D prophylaxis is not required for complete molar pregnancies. Anti D is required for partial molar pregnancies.

A lady was diagnosed with complete molar pregnancy on ultrasound- suction evacuation was done today- the lady is Rh negative and her husband is Rh positive- Should Anti D be given ?
Ans- Histopathological confirmation often takes more than 72 hours. If the diagnosis of complete molar pregnancy cannot be established within 72 hours, anti-D prophylaxis can be administered for practical
reasons.