AFJOG

REVIEW The ultrasound diagnostic features of CSP include the following: 1. An empty uterine cavity and endocervical canal 2. An early gestational sac (with or without a foetal pole) or a placenta adjacent to the hysterotomy scar or with a part penetrating the triangular niche 3. An absent or thin (<3 mm) myometrial layer between the gestational sac and bladder 4. Doppler ultrasound features showing a rich blood flow surrounding the gestational sac 6 A transabdominal approach with a full bladder has also been recommended, as this provides a panoramic view of the gestational sac, uterus and bladder. The colour doppler with grayscale assists in better defining the features of the caesarean scar pregnancy. 15 In the late first trimester and the second half of pregnancy, a CSP may be suspected during ultrasound evaluation if there is an anterior placenta situated low in the uterus opposite the bladder, if there is ballooning of the lower segment, or if there is myometrial thickness <5mm adjacent to the lower edge of the placenta with increased vascularity on doppler ultrasound. 16 ULTRASOUND PREDICTORS OF OUTCOMES OF CSP Apart from diagnostic features, several early trimester ultrasound features that aid in predicting severe outcomes of caesarean scar pregnancy have been identified. These include 1. The thickness of the anterior myometrial wall at the site of implantation 2. Type of CSP 3. Cross over Sign (COS) 17 To help predict the prognosis, CSP has been further qualitatively classified into types I – III, according to the degree of implantation into the scar and the residual myometrial thickness at the site of implantation, and graded according to the cross-over sign (COS). Type I denotes partial implantation in the scarwitha residual myometrial thickness (RMT) at the site of implantation of >3 mm. In type II there is partial implantation in the scar with RMT < 3 mm, and in type III the pregnancy is wholly implanted in the scar with the RMT <3 mm. 18 The crossover sign is established by drawing a straight line in the sagittal view of the uterus which connects the internal os and the uterine fundus through the endometrium (endometrial line). The superior-inferior diameter of the gestational sac is then traced perpendicularly. The COS is further divided into COS 1 and 2. COS 1 has a gestational sac implanted within the caesarean scar and at least two- thirds of the superior-inferior diameter (S-I) is above the endometrial line, towards the endometrial line. COS -2 is when the gestational sac is implanted within the caesarean scar with less than two–thirds of the gestational sac above the endometrial line. 19, 20 The ultrasound predictors of severe complications include a thin myometrial thickness of <3mm, consistent with type II and III CSP, and implantation into a defect within the caesarean section scar (a niche) which is consistent with a cross-over sign 1 and exogenous type of CSP. 14 DIFFERENTIAL DIAGNOSIS OF CSP Some of the clinical and ultrasound features of CSP can be confused with other conditions such as ongoing or incomplete miscarriage, cervical ectopic pregnancy or low implantation of a normal intrauterine pregnancy. A miscarriage in progress may be differentiated from CSP on ultrasound by exerting pressure with a vaginal probe on the uterus. This will result in the sliding of the sac relative to the cervical canal in a miscarriage and returning when the pressure is released. In CSP the is no movement upon applying pressure. A cervical ectopic can be differentiated from the CSP by its hourglass appearance on ultrasound due to a ballooning cervical canal. There is no myometrial thinning between the bladder and the pregnancy. A low implanted intrauterine pregnancy will neither have an hourglass appearance nor a sliding sign, but will have a normal myometrial thickness. 18,21 EARLYAND LATE COMPLICATIONS OF CSP In the first half of pregnancy, CSP can be associated with multiple complications such as spontaneous abortions, uterine rupture, life-threatening haemorrhage, emergency hysterectomy and loss of fertility. Undiagnosed or expectantly managed CSP can result in PAS. 16, 22 In the second half of pregnancy, most complications result from the associated PAS and placenta praevia that may cause antepartum haemorrhage, arteriovenous malformations, intraperitoneal bleeding, preterm labour, foetal distress and demise, severe haemodynamic instability and, maternal mortality. 13,14 Early treatment (≤9 weeks of gestation) is associated with a reduction in morbidity compared to treatment (>9 weeks). 21 PREDICTION AND PREVENTION Apart from caesarean delivery, other risk factors for CSP are not well understood. However, factors that predispose to uneven healing of the caesarean section scar with the resultant formation of thin scar pockets or niches have been suggested. 6 These include incisions in a poorly developed lower segment for elective delivery in breech presentation, repeat caesarean sections, single-layer closure of the incision, and incorporation of the endometrium during closure. The majority of caesarean scar pregnancies occur after one caesarean delivery. Other predictors of CSP that have been reported include advanced maternal age, parity >5, history of termination of pregnancy and pregnancy interval < 2 years. 1,8 GOALS OF MANAGEMENT OF CSP Appropriate treatment options for CSP should be able to meet the goals of minimising blood loss and the risk of haemodynamic instability, preserving fertility and ensuring a quick return to normal activities at an affordable cost. 23 EXPECTANTMANAGEMENTOFCSPWITHEMBRYONIC CARDIAC ACTIVITY Due to the severe morbidity and high risk of mortality associated with carrying a CSP to term, the Society for Maternal-Fetal Medicine recommended against expectant management of caesarean scar pregnancy in favour of laparoscopic or transvaginal resection and repair, or aspiration, or intragestational treatment with methotrexate despite the high rate of pregnancies carried to term. However, as part of informed consent, detailed counselling is necessary to allow the patient to make an informed choice should she prefer expectant management. The clinical factors associated with less severe complications during expectant African Journal of Obstetrics and Gynaecology | Volume 1 | Issue 2 | 2023 | 06