Main findings and interpretation
The first abdominal pregnancy was reported in 1708 as an autopsy finding
and many cases have been reported worldwide ever since (3). While in a
primary abdominal pregnancy the fertilized ovum implants directly in the
abdominal cavity (10), in a secondary abdominal pregnancy the embryo or
fetus continues to grow in the abdominal cavity after explusion from its
primary site of development (11). There are several theories about the
pathophysiology of an abdominal pregnancy. Berghella V et al
hypothesised that an omental pregnancy is secondary to a primary tubal
or ovarian pregnancy that subsequently implants on the omentum (12),
while Cavanagh stated that fertilization may occur in the posterior
cul-de-sac where sperms accumulate and the ovum is transported via
dependent flow of peritoneal fluid (13). Paternoster DM et al suggested
delayed ovulation associated with a reversed tubal course by retrograde
menstrual flow as a possible mechanism and further emphasised the role
of intraperitoneal fluid flow in carrying the zygote from the cul-de-sac
to different intraperitoneal sites (14). Dmowski et al and Hall et al
postulated a spontaneous migration of the embryo from the uterus to the
retroperitoneal space along lymphatic channels (15,16). Abdominal
pregnancies post hysterectomy have been explained by migration of the
fertilised ovum via fistulous tracts (17).
Though the ectopic pregnancy rates are on an incline, the risk of
abdominal pregnancies, with ruptured ectopic pregnancy among one of its
many causes, is on a declining trend due to improved antenatal care and
diagnostic methods (11). Despite the availability of defined criteria by
Studdiford, its diagnosis proves challenging and requires a high degree
of suspicion. In addition to its vague non-specific clinical
presentation, initial misdiagnosed ultrasound reports may interfere with
timely diagnosis, like in our case. The most common physical examination
findings include abdominal tenderness (100%), abnormal fetal lie
(70%), easily palpable fetal parts and a displaced cervix (9). Our
patient presented with symptoms of generalised pricking abdominal pain,
mild chest pain and spotting per vagina at 13 weeks of gestation. This
vague presentation was misleading and resulted in a delay in diagnosis
till evaluation at our centre. More often than not a transvaginal
ultrasound confirms the diagnosis but in case of a dilemma, MRI can
provide further clarity regarding the diagnosis.
Gestational age at diagnosis and maternal hemodynamic stability are the
main factors dictating management. The two main modalities of treatment
are medical and surgical, surgical being more common as patients usually
present as an acute emergency with intra-abdominal bleeding (4). The
choice between laparoscopy and laparotomy depends on multiple factors
including period of gestation at diagnosis, maternal hemodynamic
stability and availability of resources and skill (18). With increasing
early ultrasonography, ectopic pregnancies are being identified prior to
complications like rupture, providing an opportunity to attempt medical
management with KCl or methotrexate individualised for each case (4).
Less commonly used agents include hyperosmolar glucose, prostaglandins,
danazol, etoposide and mifepristone (18).
The management of the placenta ranges from complete or partial removal
of the placenta to leaving the complete placenta in situ (18). The use
of adjuvant methotrexate for the placental remnants is controversial.
While some believe that it helps accelerate the involution of the
placenta others say that rapid degeneration results in higher amounts of
necrotic tissue accumulation forming a nidus for infection thereby
increasing sepsis rates (18). The use of methotrexate at advanced
gestation is debatable, as it works best on rapidly dividing cells and
is less likely to help in case of a mature placenta (19). We did not
administer methotrexate to our patient as very minimal placental tissue
<1 cm was left behind.
Abdominal pregnancy, especially when advanced, is known to be associated
with high maternal and neonatal morbidity and mortality (18). The
maternal mortality rate ranges from 0.5-20% (20). Severe hemorrhage,
perforation, bowel obstruction, fistula, disseminated intra-vascular
coagulation and sepsis contribute to the increased morbidity and
mortality. Our patient was transfused with 3 units of packed red blood
cells and 2 units of fresh frozen plasma and did not have any other post
operative morbidity. Perinatal mortality rates of 40%-95% have been
reported and 21-90% of surviving fetuses have serious birth defects due
to anhydramnios and subsequent compression and also vascular disruption
(20). Surviving neonates frequently develop torticollis, flattening of
the head, facial or cranial asymmetry, thoracic malformations, limb
defects, joint abnormalities and CNS malformations (9,20).
In a systematic review done by Poole A et al on 225 abdominal
pregnancies diagnosed/treated at less than 20 weeks of gestation, from
1965 to 2009, 8% of the early abdominal ectopics occurred with an
intrauterine device in situ. Mean gestational age at treatment was 10
weeks. The commonest sites of early abdominal ectopics were pouches
around the uterus (24.3%), serosal surface of uterus and tubes (23.9%)
and other sites (12.8%). Primary surgical management was done in 208
cases (87.8%). Non-surgical adjuvant or primary therapy included
intramuscular methotrexate, intralesional methotrexate, intracardiac KCl
and uterine artery embolization. The overall maternal mortality was 3%
(4).
Nkusu ND et al reviewed 163 cases of advanced abdominal pregnancy after
20 weeks of gestation from 1946 to 2008. Forty five percent cases were
diagnosed preoperatively. Fetal/ perinatal mortality was 72% and
pressure deformities were common among survivors. Maternal postoperative
complications like hemorrhage and infection were noted in 55%,
transfusion of blood products in 80%. Maternal mortality was 12% (20).
In the current review of 314 cases of early and advanced abdominal
pregnancy by various authors from 1930-2021, we observed a maternal
morbidity in terms of transfusion of blood and blood products in 74
cases (23.6%) and maternal deaths in 15 cases (4.8%). The maternal
mortality rate we noted in our review is marginally higher than the
systematic review done by Poole A et al(4) but is significantly lower
compared to the rate quoted by Nkusu ND (12%)(20). This difference
could be attributed to the period of gestation used as inclusion
criteria. Early versus advanced abdominal pregnancy is an important
factor influencing the varied maternal mortality and morbidity rates
reported by different authors and higher rates have been reported at
advanced gestations. We also noted that 93.9% of the cases were
surgically managed and 6% required hysterectomy. These rates are
comparable to that noted by Poole A et al. In addition, multiple other
factors may have contributed to the reduction in maternal mortality
rates over the years like early diagnosis, advanced imaging modalities,
increased patient and physician awareness, improved surgical and
non-surgical techniques, blood product availability and better access to
tertiary care centres over the years. Regarding the overall neonatal
outcome, 8.6% were live born, 76.8% were fetal loses <20
weeks of gestation, 14.6% were IUFD/ stillborn and 1.9% were neonatal
deaths.