Advanced Abdominal Pregnancy

This blog post comprises of important points taken from the TOG article ‘Advanced abdominal pregnancy’ published in July 2022. It is strongly recommended to read the full article to have a complete understanding of this topic as this post is just a quick summary.

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Introduction

• Abdominal pregnancy — when implantation occurs within abdominal cavity / an extra uterine pregnancy in which all or most of the foetus develops within the abdominal cavity
• A rare form of ectopic pregnancy 
• Incidence ~1% of all ectopic pregnancies
• Associated maternal mortality  0-12% 
• Overall risk of maternal death 7x that of ectopic pregnancy 90x that of an intrauterine pregnancy
• Fetal survival >78%

Classification

Based on gestation at diagnosis

• Early Abdominal Pregnancy (EAP) - before 20 weeks
• Advanced Abdominal Pregnancy (AAP) - after 20 weeks

Based on site of implantation 

• Primary abdominal pregnancy — implantation directly occurs in the abdominal cavity
• Secondary abdominal pregnancy — when conception extruded from its primary site of implantation and re-implants in abdominal cavity (usually after ruptured ectopic)

Risk Factors

• Most have no identifiable risk factors
• Risk factors are same as any other ectopic pregnancy — tubal pathology, in situ IUCD, previous ectopic 
• Uterine anomalies & history of previous uterine surgery (esp CS) are associated with abdominal pregnancy
• AAP can also occur post scar rupture, previous myomectomy and post uterine perforation at surgical TOP, after IVF

Clinical Presentation

• Diagnosis is often missed & usually made after fetal demise
• Only 50% diagnosed before surgery
• High suspicion is key to pre-operative diagnosis
• No specific S&S of AAP

Symptoms 

• Commonest presentation — abdominal pain ± vaginal bleeding (pain often persistent & increases by fetal movements)
• Bloating & vomiting

Signs 

• None pathognomonic
• Reasonable sign of AAP - displaced cervix (anteriorly) 
• Others— severe anaemia, abnormal fetal lie, oligohydramnios, SGA 

Ultrasound 

• Abdominal pregnancy hard to diagnose with advancing gestation
• Any first-trimester scan should include - location of gestational sac in relation to cervix, endometrial cavity and uterus
• Intraabdominal pregnancy suspected on USG — extrauterine amniotic sac & an empty uterine cavity - foetus & placenta outside uterus, lack of uterine myometrium around foetus 
• Skills & techniques of sonographer matters

If AAP suspected on USG — Must do MRI

MRI

• Imaging modality of choice — mainstay for surgical planning
• In addition to showing foetus with placenta outside uterine cavity, MRI can also evaluate sites of placental attachment to surrounding visceral organs (bowel, liver, spleen)
• Follow MRI reporting protocol after intraabdominal pregnancy discovered - which includes information about foetus, amniotic sac, placenta, uterus, presence of intra-abdominal fluid or haemoperitoneum, maternal findings and comorbidities

Management 

• Depends on gestation at diagnosis 
• EAP — TOP recommended
• AAP — need to consider a few things
• At viable gestation — delay surgical delivery until acceptable level of fetal maturity
• At threshold of viability — unique challenge as no evidence-based approach 
• Need MDT approach, informed consent and consideration of ethical issues

Pregnancy termination

• Pre-viable AAP diagnosed — TOP recommended 
• In UK feticide to done if GA >21+6 wks usually by intracardiac KCL

Expectant management 

• If no other complicating factors — possible to have successful outcome (after comprehensive counselling)
• Minimum requirements for expectant management of AAP are: Confirmed diagnosis, Known placental location, Inpatient stay, Regular assessment of maternal/fetal wellbeing, 24-hr access to blood products, Access to intervention radiology, MDT input

Timing of delivery

• Individualised
• Increased risk of gestational sac beyond 34 wks
• Consider delivery from 30 wks

Surgical planning and management

• Only mode of delivery for AAP is surgical 
• Delivery can be scheduled - but emergency delivery indicated in case of maternal instability
• Surgical planning is key for optimal fetal/maternal outcomes
• Preoperative measures to minimise bleeding — build up Hb, keep blood products & cell salvage 
• Keep patient in hospital and arrange transfer to tertiary-care centre with 24-hr access to intervention radiology
• MDT meeting — to be arranged
• MRI will guide about placenta location 
• Midline or paramedical laparotomy under GA
• Foetus delivered without disturbing placenta
• Assess bleeding regularly and essential to communicate among surgeon/anaesthetist
• Rate of hysterectomy — 12%
• Unilateral / Bilateral scalping-oophorectomy or adnexectomy — 12%

The placenta 

Placental site — can be single or multiple structures within abdominal cavity

• Commonest cause of abdominal pregnancy morbidity/mortality — deep implantation of placenta on highly vascular intra-abdominal structures
• Commonest sites of implantation — uterus/adnexa
• Better outcomes with uterine implantation
• Management of placenta — no consensus

Options — removal at delivery time or leaving placenta behind

• Leaving the placenta increases risk of maternal morbidity ( placenta mass abscess, sepsis, necrosis)
• Requires regular follow-up with beta HCG
• Structural involution takes up to 5.5 years
• Hormonal decline is rapid 10 days to 7 weeks
• Methotrexate (to accelerate resorption) not recommended routinely as it is associated with significant risk of infection
• Surgical removal of placenta successful in 55-69% 

Current consensus — establish the safest management based on MRI, if safe to do, removal at surgery is preferred. If placenta cannot be safely removed, cord should be clamped and cut as close as possible to the placental mass. Placenta left in situ with monitoring

Complications

Fetal

• Oligohydroamnios, pulmonary hypoplasia, compressive deformities 
• Fetal deformation and malformation — 21% (vs background risk of 2% & 4% respectively)
• FGR — 24%
• Intraabdominal fetal demise — 36%
• PMR — 72-83%

Maternal

• Greatest risk is life-threatening intraabdominal haemorrhage 
• Need laparotomy 30% Blood transfusion needed in 70-90%
• Persistent or worsening abdominal pain
• Acute intestinal obstruction
• Bilateral ureteral obstruction
• Bilateral hydronephronsis
• Infective complications ( wound infection, placental abscess, fistulas, peritonitis) 15%

Conclusion

• AAP potentially life-threatening condition
• Keep a high index of suspicion for diagnosis
• No unified consensus to managing these patients 

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