How Long Can A Molar Pregnancy Go Undetected?

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How Long Can A Molar Pregnancy Go Undetected?

A molar pregnancy is diagnosed by an ultra sound scan. It is difficult to diagnose molar pregnancy by the symptoms and signs as these can be present even in other conditions. Usually most women with molar pregnancy would not have symptoms and most of the molar pregnancy would be detected in the routine dating scan which is done usually within 8 weeks to 12 weeks. therefore, molar pregnancy can go undetected until about 12 weeks which is the first trimester. But sometimes if the woman does not know she is pregnant or if she does not attend the antenatal visit or do the dating scan or any other scan and does not have any symptoms, molar pregnancy can go undetected until about 16 -20 weeks. It will be detected late when the other complications such as pregnancy induced hypertension, preeclampsia, thyroid diseases, thromboembolism occurs and by this time it would be too late.

Complete Molar Pregnancy

The diagnosis of complete molar pregnancy can be almost always made by an ultrasound scan. Earlier days the diagnosis made quite late and the molar pregnancy appears in the scan as the “snowstorm pattern” of the uterus, however, this is not commonly seen now as most of the molar pregnancies are identified at an earlier stage. The characteristic feature seen in a complete molar pregnancy from an ultrasound is a vesicular sonographic pattern. This occurs because the chorionic villi proliferate with vacuolar swelling.

First trimester complete molar pregnancy appears as a complex and echogenic intrauterine mass containing many cystic spaces. Sometimes a large central fluid collection can be seen which can be interpreted as an anembryonic gestation or abortion. Occasionally, there can be a central mass with variable echogenicity because the villi are too small to be seen form the scan during that period.

Studies have shown that complete molar pregnancy cannot be diagnosed accurately by an ultras sound scan, therefore histological examination of the removed tissues is important to come to an accurate diagnosis. If histology is inconclusive DNA analysis of the removed tissue should be carried out for a definitive diagnosis. Genetic marker analysis using polymerase chain reaction is accurate and very rapid in diagnosing and classifying complete and partial molar pregnancy. There is a 15% of a complete molar pregnancy to recur in the future.

Partial Molar Pregnancy

It is difficult to distinguish partial molar from complete molar pregnancy; however, presence of fetal parts or retarded fetus is helpful in diagnosing partial molar from an ultrasound scan. The ultrasonic features of partial molar are enlarged or thickened placenta compared to the uterine size, cystic spaces within the placenta, an alive or dead well formed but deformed fetus, an empty gestational sac or a sac with an ill-defined fetal echo.

Similarly, in complete molar pregnancy it is not always possible to diagnose a partial molar accurately from an ultrasound scan, therefore histological examination of the removed tissue is important. If histology is inconclusive DNA analysis of the removed tissue should be carried out for a definitive diagnosis. Genetic marker analysis using polymerase chain reaction is accurate and very rapid in diagnosing and classifying complete and partial molar pregnancy. There is a 3% of a partial molar pregnancy to recur in the future.

Conclusion

A molar pregnancy is diagnosed by an ultra sound scan. It is difficult to diagnose molar pregnancy by the symptoms and signs as these can be present even in other conditions. Usually most women with molar pregnancy would not have symptoms and most of the molar pregnancy would be detected in the routine dating scan which is done usually within 8 weeks to 12 weeks. therefore, molar pregnancy can go undetected until about 12 weeks which is the first trimester. But sometimes if the woman does not know she is pregnant or if she does not attend the antenatal visit or do the dating scan or any other scan and does not have any symptoms molar pregnancy can go undetected until about 16 to 20 weeks.

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