Extra-uterine pregnancy/ectopic gestation

Published on 10/03/2015 by admin

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Last modified 10/03/2015

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Chapter 12 Extra-uterine pregnancy/ectopic gestation

CHAPTER CONTENTS

Aetiology 107
Outcome for the pregnancy 107

Tubal abortion 107
Tubal rupture 107
Secondary abdominal pregnancy 108
Clinical aspects 108

Subacute 108
Acute – dramatic 108
Diagnosis 110
Treatment 111
Prognosis 112

Most extra-uterine pregnancies occur in the Fallopian tubes (ectopic gestation) but, rarely, the fertilized ovum may implant onto the ovarian surface or the uterine cervix. Extremely rarely, the fertilized ovum implants onto the omentum (abdominal pregnancy).

One in 90 pregnancies is ectopic and in the United Kingdom this results in the death of 3 to 4 women each year. A combined intra-uterine and extra-uterine pregnancy is very rare and occurs 1 : 40 000 spontaneous pregnancies and 1 : 1000 IVF pregnancies.

AETIOLOGY

The aetiology of most cases of ectopic gestation is not known. Implantation of the fertilized ovum can only take place when the zona pellucida has partially or completely disappeared. Premature implantation could occur if the passage of the fertilized ovum along the Fallopian tube is delayed because of tubal damage following infection. Premature implantation may occur in:

• The fimbriated end of the Fallopian tube (in 17% of cases)
• The ampulla (in 55% of cases)
• The isthmus (in 25% of cases)
• The interstitial portion of the tube (in 2% of cases) (Fig. 12.1).
image

Fig. 12.1 Sites of ectopic gestation implantation, with the relative frequency of occurrence.

OUTCOME FOR THE PREGNANCY

In most cases the pregnancy terminates, in one of several ways (see below), between the sixth and 10th weeks.

Tubal abortion

This occurs in 65% of cases and is the usual outcome in fimbrial and ampullary implantation (Fig. 12.2). Repeated small haemorrhages from the invaded area of the tubal wall detach the ovum, which dies and:

• Is absorbed completely
• Is aborted completely through the tubal ostium into the peritoneal cavity
• Is aborted incompletely, with the result that the clot-covered conceptus distends the ostium
• Forms a tubal blood mole.
image

Fig. 12.2 Sequelae of tubal abortion.

Tubal rupture

This occurs in 35% of cases and is more common when the implantation is in the isthmus. Whereas the rupture of the ampulla usually occurs between the sixth and 10th weeks, rupture of the isthmus occurs earlier, frequently at the time of the first missed period. The trophoblast burrows deeply and eventually erodes the serosal coat of the tube, the final break being sudden or gradual. Usually the ovum is extruded through the rent and bleeding continues. If the rupture is on the mesenteric side of the tube, a broad ligament haematoma will form (Fig. 12.3).

image

Fig. 12.3 Sequelae of tubal rupture.

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