A full term abdominal pregnancy with an isthmic tubal implantation of the placenta

Abdominal pregnancy is rare. It represents approximately 1% of ectopic pregnancies [3] which incidence reaches 2% [4]. The abdominal pregnancy’s incidence seems to be greater in developing countries where sexually transmitted diseases with tubal lesions would be common [1, 2, 5]. Its evolution towards the term seems also to be more frequent in these same countries poorly equipped and medicalized [1, 2].

The implantation of the embryo in the abdominal cavity can be primitive or secondary. It is primitive in case of direct implantation of the embryo in the abdominal cavity. It is secondary when it occurs after a ruptured tubal pregnancy or a tubal abortion or even a uterine rupture or perforation [3, 5]. Secondary implantation is the most common [1, 6, 7]. In our case the abdominal location is secondary because the embryo was first inserted into the tubal isthmus, as shown by the implantation of the placenta into this part of the tube. The development of the fetus took place in the abdominal cavity, through the wall of the ruptured isthmus. The diameter of the isthmus is small, 2 mm [8], so its rupture probably occurred early, at least in the first trimester [6].

The diagnosis of abdominal pregnancy is difficult [3, 5], and is an intra-operative finding in 40 to 50% of cases [3, 5], despite antenatal follow-up and ultrasound scan. The evolution of abdominal pregnancy when it is asymptomatic [3, 9], as in our case, raises the question of whether the clinical examinations were carried out appropriately. One would expect signs of hemoperitoneum and shock, as part of the tubal rupture leading to secondary abdominal implantation. Their absence could in our case be explained by the fact that the embryo, part of which (placenta) was still intratubal, herniated through the ruptured tubal wall, has caused a hemostasis by compression of the vessels of the rupture banks. For Worley et al. [6] the clinical expression of abdominal pregnancy is variable, depending on the degree of the anatomical distortion it creates and the placental insertion site.

Clinical signs are therefore not specific, but for some authors [1‐3, 5, 6], the following signs should bring the practitioner to think about the diagnosis: abdominal pain with intestinal transit disorder, abdominal pain during active movements of the fetus, spreading of the abdomen due to an irregular presentation, palpation of the fetal parts under the maternal abdominal wall, cervix deviated under pubis symphysis, failure to trigger childbirth labor. Unfortunately most of these signs only appear during already advanced abdominal pregnancies, as with our patient.

The ultrasound scan which was not done in our case because of the under-equipment of our health centers, should be done early in the first trimester, to specify the location of the pregnancy and at the same time the correct gestational age [4]. At this time of pregnancy, the risk of missing the diagnosis of ectopic pregnancy is lower [4, 9]. For best results, it is better to do this transvaginally, paying particular attention to the ovaries and the uterine wall [3]. In the second and third trimesters, the risk of misrecognizing abdominal pregnancy is important, and has reached more than 50% in some series [7, 9]. For Allibone et al. [10] absence of uterine wall between maternal bladder and fetus, ectopic location of placenta, abnormal presentation of fetus, proximity of fetal parts to maternal abdominal wall and absence of amniotic fluid between placenta and the fetus, are the ultrasound features of abdominal pregnancy.

Measurement of serum β-hCG is also used in the diagnosis of early ectopic pregnancies. When an initial measurement is performed, a threshold of more than 1500 IU / L associated with an empty uterus on endovaginal ultrasound should suggest an ectopic pregnancy [8]. Serial measurements of β-hCG levels can also be performed in patients with possible ectopic pregnancy. For Heather et al. and Surampundi et al. these measures may have been elevated, sometimes as in an intrauterine pregnancy, in decline or level of β-hCG levels, and therefore require caution in their interpretation [11, 12] which should be associated with the clinical and ultrasound results to achieve a correct diagnosis [12]. In case of persistent doubt despite ultrasound and measurement of β-hCG, MRI can be used to clarify the diagnosis [6].

The treatment of abdominal pregnancy is surgical, at best by laparotomy, for a better control of the hemorrhagic risk related to the extraction of the placenta [1, 5, 7]. This extraction is justified only if it is easily achievable, with a lower hemorrhagic risk [2, 5]. Otherwise the placenta left in place will gradually and spontaneously resorb in the post operative course. The use of methotrexate to accelerate this resorption is controversial for it would involve a greater risk of infection due to an accelerated placental necrosis [3, 5, 6].

In our case, after fetal extraction, we performed a total left salpingectomy which allowed removing the placenta in the same time. An attempt at placental detachment would have been hemorrhagic and would have laminated the tube, the preservation of which might have given rise to another ectopic pregnancy later. For many authors [1, 9, 13], the ablation of the placenta is associated with a better maternal prognosis, as in our case. When the placenta is left in place, it is necessary to keep watch over the appearance of the following maternal complications in postoperative period: bowel obstruction, infection, hemorrhage, anemia, fistula, [1, 9, 13] etc. These complications can worsen the maternal prognosis, with a lethality up to 18% [1, 5, 7]. The fetal prognosis varies with the gestational age. When the diagnosis is early, before 20 weeks [14], it is unlikely that the pregnancy will be preserved [3, 14]. At a later age, a rigorous monitoring can allow the extraction of the live newborn as soon as the period of fetal viability is reached [3]. Otherwise, when the diagnosis is late, or when it is done intra-operatively, the fetal prognosis is often very pessimistic, like in our case, with a perinatal mortality which varies between 40 and 95% according to authors [1, 5, 6, 9, 13].