Obstetrics Simplified - Diaa
Hydatidiform (Vesicular) Mole
It is a benign neoplasm of the chorionic villi.
1:2000 pregnancies in United States and Europe, but 10 times more in
Asia. The incidence is higher toward the beginning and more toward the end
of the childbearing period. It is 10 times more in women over 45 years old.
- The uterus is distended by thin walled, translucent, grape-like
vesicles of different sizes. These are degenerated chorionic villi filled
- There is no vasculature in the chorionic villi leads to early death
and absorption of the embryo.
- There is trophoblastic proliferation, with mitotic activity affecting
both syncytial and cytotrophoblastic layers. This causes excessive secretion
of hCG, chorionic thyrotrophin and progesterone. On the other hand, oestrogen
production is low due to absence of the foetal supply of precursors.
- High hCG causes multiple theca lutein cysts in the ovaries in about
50% of cases. It also results in exaggeration of the normal early pregnancy
symptoms and signs.
- Complete mole:
- The whole conceptus is transformed into a mass of vesicles.
- No embryo is present.
- It is the result of fertilisation of anucleated ovum (has no
chromosomes) with a sperm which will duplicate giving rise to 46
chromosomes of paternal origin only.
- Partial mole:
- A part of trophoblastic tissue only shows molar changes.
- There is a foetus or at least an amniotic sac.
- It is the result of fertilisation of an ovum by 2 sperms so
the chromosomal number is 69 chromosomes.
DIFFERENTIATION BETWEEN COMPLETE AND PARTIAL MOLE
|Embryonic or foetal tissue
|Swelling of the villi
||Paternal 46 XX (96%) or 46 XY (4%)
||Paternal and maternal 69 XXY or 69 XYY
- Amenorrhoea: usually of short period (2-3 months).
- Exaggerated symptoms of pregnancy especially vomiting.
- Vaginal bleeding which is usually dark brown and may be associated
with passage of vesicles.
- Abdominal pain: may be,
- dull-aching due to rapid distension of the uterus,
- colicky due to starting expulsion,
- sudden and severe due to perforating mole.
- General examination:
- Pre-eclampsia develops in 20% of cases, usually before 20 weeks’
- Hyperthyroidism develops in 10% of cases manifested by enlarged
thyroid gland, tachycardia and elevated plasma thyroxin level.
- Breast signs of pregnancy.
- Abdominal examination:
- The uterus is larger than the period of amenorrhoea in 50% of
cases, corresponds to it in 25% and smaller in 25% with inactive
or dead mole.
- The uterus is doughy in consistency
- Foetal parts and heart sound cannot be detected except in partial
- Local examination:
- Passage of vesicles (sure sign).
- Bilateral ovarian cysts (5-20 cm) in 50% of cases.
- Urine pregnancy test: is positive in high dilution. 1/200 is highly
suggestive, 1/500 is surely diagnostic. In normal pregnancy it is positive
in dilutions up to 1/100.
- Serum β-hCG level: is highly elevated (>100000 mIU/ml).
- Ultrasonography reveals:
- The characteristic intrauterine "snow storm" appearance,
- no identifiable foetus,
- bilateral ovarian cysts may be detected.
- X-ray: shows no foetal skeleton.
- Infection due to absence of the amniotic sac.
- Perforation of the uterus.
- Pregnancy induced hypertension
- Subsequent development of choriocarcinoma
- As soon as the diagnosis of vesicular mole is established the uterus
should be evacuated.
- The selected method depends on the size of the uterus, whether partial
expulsion has already occur or not, the patient's age and fertility
- Cross- matched blood should be available before starting.
- It is carried out under general anaesthesia, but not that which
relax the uterus as halothane as it may induce severe bleeding.
- An infusion of 20 units oxytocin in 500 m1 of 5% glucose should
be maintained throughout the procedure.
- Dilatation of the cervix is done up to a Hegar's number equal to
the period of amenorrhoea in weeks e.g. No. 10 Hegar for 10 weeks’ amenorrhoea.
The suction canula used will be of the same size also.
- A suction canula which may be metal or a disposable plastic (preferred)
is introduced into the uterine cavity.
- The canula is connected to a suction pump adjusted at negative pressure
of 300-500 mmHg according to the duration of pregnancy.
- Although some recommended a gentle sharp curettage to the
uterus after evacuation, it is preferable to wait one week for fear
of uterine perforation.
It may be needed for evacuation of a large mole to minimise and facilitate
control of bleeding.
It should be considered in women over 40 years who have completed their
family for fear of developing choriocarcinoma.
Oxytocins and / or prostaglandins may be used to encourage expulsion
of the mole but must always be followed by surgical evacuation.
- As choriocarcinoma may complicate the vesicular mole after its evacuation,
detection of serum ß-hCG by radioimmunoassay for 2 years is essential.
- Detection is done every;
- 2 weeks after evacuation to ensure regression of b -hCG level
- every month for one year then,
- every 3 months for another year.
- Persistent high level indicates remnants of molar tissues which
necessitate chemotherapy (methotrexate) with or without curettage.
Hysterectomy is indicated if women had enough children.
- Rising hCG, level after disappearance means developing of choriocarcinoma
or a new pregnancy. So combined contraceptive pills should be used for
prevention of pregnancy which can be misleading.
- It is expected that urine pregnancy test is negative 4 weeks after
evacuation and serum β-hCG is undetectable 4 months after evacuation.
- Early features suggesting residual molar tissue include:
- recurrent or persistent vaginal bleeding,
- failure of uterine involution,
- persistence of ovarian enlargement.
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Edited by Aldo Campana,