Caesarean scar pregnancy is one of the rarest forms of ectopic pregnancy. The re- ported incidence of Caesarean scar pregnancies is 1:1800 to 1:22161, 2 pregnancies although the overall prevalence seems to be increasing. The true incidence of ectopic pregnancy in previous Caesarean scar has not been determined because very few cases have been reported in medical literature till now, the first of which was reported in 19783. The increase in the incidence of Caesarean scar pregnancies may reflect an increased incidence in Caesarean sections being carried out and easy availability of transvaginal sonography for diagnosis. Pregnancy in a Caesarean Section scar has increased risk of serious complications such as placenta accrete, invasion of bladder, rupture of scar which may require hysterectomy and can cause significant maternal morbidity and mortality.
The exact mechanism of implantation into the scar is not very well understood. However it has been hypothesized that the blastocyst enters through micro tubular tracts between the scar tissue and the uterine cavity4,5.
A number of risk factors6 have been associated for development of Caesarean scar pregnancy including previous uterine procedures such as dilatation and curettage, in-vitro fertilization, prior placental pathologies and prior ectopic pregnancies.
Although some have suggested that the number of previous cesarean deliveries may increase the risk1 of subsequent cesarean scar pregnancy due to increased scar surface area, a larger review showed that approximately half of patients had only one prior cesarean delivery6,7.
37 years old 6th Gravida, IVF-ET conceived, presented with pv spotting and positive beta hCG.
She has one living issue delivered by Caesarean section. Her previous pregnancies include three ectopic gestations (right tubal, left tubal and cornual) for which bilateral laparoscopic salpingectomy has been performed. She also had one missed abortion (IVF conception) for which dilatation and curettage was performed.
Her current pregnancy was an IVF conception with single blastocyst transfer. Her beta hCG done two weeks post transfer was positive with a value of 3161 (gestational age 4weeks 4 days).
She had light pv spotting from for 5 days after beta hCG was positive. She did not have any other presenting complaints.
Transvaginal Sonography performed at gestational age 6weeks 2 days showed a single live embryo corresponding to 6 weeks 2 days situated in the myometrial gap at the site of previous Caesarean scar. The surrounding chorionic reaction reached upto the uterine surface, without any intracavitary component.
Two approaches for termination were considered. One was Transvaginal USG guided aspiration of products and the other was laparoscopic excision of ectopic.
Transvaginal approach was considered in this case, as it would give the patient a chance for future conception as opposed to laparoscopic excision which would considerably decrease the uterine wall thickness, leading to an early rupture.
Her beta hCG repeated the next day (6weeks 3days) had a value of 45,472. Transvaginal USG guided aspiration of the embryo and amniotic fluid was done and 0.4cc of Injection Methotrexate was instilled into the gestational sac and surrounding decidual tissue.
The absence of fetal pole was confirmed on USG and the procedure was uneventful.
The beta hCG levels were repeated 4 days later was found to be 19,623.
Repeat Transvaginal sonography confirmed the absence of fetal pole and embryo and presence of lytic decidual reaction.
The implantation of a blastocyst in the previous Caesarean scar is a rare but life-threatening form of ectopic pregnancy. This is due to the high risk of uterine rupture and its related maternal morbidity and mortality.
There are two types of Caesarean scar pregnancies described8: one with a progression towards the normal uterine cavity, the other is a deeper implantation, likely to invade bladder and other structures. The latter type is at greater risk for rupture.
The presenting complaints may be similar to those of other types of ectopic pregnancy including light spotting per vaginum, abdominal pain in addition to amenorrhea. In some cases the woman may be asymptomatic9.
Any sign of hemodynamic instability would indicate a rupture or impending rupture. In a patient with impending rupture, one would be able to demonstrate uterine tenderness at previous scar site.
The first line of diagnosis for a Caesarean scar ectopic is transvaginal ultrasound4, 5. The transvaginal USG findings should include: an empty uterine cavity and cervical canal without any contact of gestational sac, presence of a gestational sac with fetal pole in anterior part of uterine isthmus and absence of or defective myometrial tissue between bladder and sac.
Some recommend a combined approach: transvaginal for detailed study of gestational sac along with its relation to scar and an abdominal scan to see the relationship with the bladder.
A Doppler study may be performed to demonstrate peritrophoblastic flow around the sac. A 3 D ultrasound enhances accuracy by helping to identify finer details2,4,8.
Magnetic Resonance Imaging (MRI), is a useful tool, however it takes time for the acquisition of report and is also costly.
Laparoscopy can be used for diagnostic and therapeutic purposes.
With the imminent threat of rupture of scar, the treatment of Caesarean scar pregnancy is termination. The patient can be treated conservatively with systemic methotrexate in a regimen similar to that for tubal ectopic pregnancy. Medical line of management is acceptable for unruptured pregnancies with less than 8 weeks duration with considerable thickness between the myometrium and urinary bladder. Consent for surgical intervention however, must be taken.
Sac aspiration under ultrasound guidance can be performed, along with local injection of embryocidal agent such as methotrexate, potassium chloride, hyperosmolar glucose etc. Double lumen 16 gauge needle used for oocyte retrieval have been used, which allows aspiration of products through one lumen and instillation of embryocidal agent through other lumen.
Serial beta hCG titres are carried out to confirm successful aspiration of the products.
Caesarean Scar pregnancies are still a rare entity despite an increased Caesarean section rate worldwide.
Early diagnosis and management can help in avoiding life-threatening complications, which could affect future fertility and contribute to maternal mortality.
As this a very rare entity, there is no conclusion as yet as to the best treatment modality. From all the treatment options available, none appears to be entirely advantageous over the other with respect to retaining integrity of the uterus.
Further studies are required to conclude whether there is any association between Caesarean section technique and increased risk of scar ectopic, time between Caesarean and scar ectopic and regarding treatment options.
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