PARTIAL MOLAR PREGNANCY

1. Uterine signs.
• Gestational sac:
• Empty.
• May contain amorphous echoes.
• May contain a growth retarded fetus.
• Ratio of transverse / antero-posterior diameter of the gestational sac >1.5.
• Irregularity or increased echogenicity of the maternal-embryonic interface.
• Enlargement ± 4%.
2. Ovarian signs.
• Theca lutein cysts are rarely seen.
3. Placental signs.
• Placenta excessively enlarged (>4mm at 18-22 weeks).
• Cystic spaces within placenta (Swiss cheese appearance).
4. Fetus.
• Growth restriction (severe in > 70%). Usually present from 16 weeks onwards.
• Structural fetal defects in 93%, especially hands, heart, micrognathia and ventriculomegaly.
• Triploid fetus.

	Growth restricted fetus Enlarged placenta with cystic spaces
Partial Molar Pregnancy Growth Retardation and Swiss Cheese Appearance Placenta
Partial Mole - Placental signs Cystic spaces within placenta

5. Doppler studies.
• Normal or high uterine arterial resistance to flow.

DIFFERENTIAL DIAGNOSIS

1. Triploidy.
2. Diploid / triploid mosaicism may appear as a triploid partial mole.
3. Benign hydropic villous degeneration.
4. Villous hydatidiform transformations have been demonstrated in association with tetraploidy, autosomal trisomy and monosomy X.
5. Beckwith-Wiedermann syndrome - hydrops of the stem villi with placentomegaly and a normal trophoblast and phenotypically normal fetus has been reported. This appears to be a limited malformation of the extraembryonic mesoderm involving the mesenchyme and vessels of the stem villi of central cotyledons and is therefore referred to as mesenchymal dysplasia.
6. Normal pregnancy adjacent to a leiomyoma.