Ovarian cysts occur to 4.9% of pregnant women . Ovarian cysts of the giant-type are extremely rare in the gravid-puerperium period. They represent less than 1‰ of the set of cysts associated with pregnancy  and their symptoms are non-specific. Generally, such symptoms as abdomen discomfort, constipation, back or abdominal pain are attributed to regular manifestations of pregnancy. So, these symptoms may be neglected by both the patient and the physician. The following could help discover the cyst before it became large:
- a complication such as torsion. This torsion often occurs when the cyst has between 6 and 8 cm diameter, with almost 60% of instances happening during 10–17 weeks of gestation.
- a systematic ultrasound carried out for the monitoring of the pregnancy. However, the place where our patient resided, no ultrasound was available.
Imaging plays a big role in diagnosis. Compared to ultrasound, Computed tomography (CT) and magnetic resonance imaging (MRI) (which is better than CT) are the best means of analysis of the cyst [7, 8]. In the present case, CT was used because MRI was too expensive for our patient. The majority of the cysts are asymptomatic and regress spontaneously . When the cyst is large, it can compress the gravid uterus, slow the fetus intra-uterine growth, cause premature delivery or abnormal presentation of the fetus. In the postpartum, the giant cyst is a risk factor for haemorrage. In our case, vaginal delivery has been possible with no complications.
The differential diagnosis of an abdominal mass includes benign and malignant gynecologic and non-gynecologic etiologies. A giant ovarian cyst can provoke a differential diagnostic problem with another fluid abdominal mass. In the present case, imaging had evoked both a giant ovarian cyst and a huge mesenteric cyst. Correct preoperative diagnosis is quite difficult due to the rare occurrence or the lack of specific clinical presentation of the giant ovarian cyst. Common symptoms, due to compressive effect such as abdominal pain, distension, bloating, constipation and vomiting can arise. Before surgery, two main arguments made us to think of a giant ovarian cyst rather than a huge mesenteric cyst: the female sex of our patient, and the rarity of mesenteric cysts. In fact, mesenteric cysts are often found among the paediatric population with an annual incidence of 1 for 20,000 and are very rare in the adult population with an annual incidence of only 1 for 100,000 .
The management approach depends on the size of cyst, equipment, and level of surgeon’s experience. According to many authors, aspiration of the contents of the cyst should be avoided because of complications such as infection, bleeding, rupture of the cyst, increased risk of peritoneal adhesion [11,12,13]. Yet, surgery can be done laparoscopically. In so doing, after the introduction of the trocars, an aspiration of the contents of the cyst is made before its removal . But this laparoscopy is not recommended when the cyst is suspected of malignancy because of the risk of spreading cancer cells [13, 14]. In our case, we preferred a laparotomy because we were not sure of the benign nature of the cyst preoperatively. Furthermore, laparoscopy surgery was not possible due to the large size of the cyst.
An immediate complication to be feared when removing a giant ovarian cyst is the vacuum shock requiring a good preventive vascular filling . In the literature, cases of giant ovarian cysts during pregnancy or postpartum have rarely been reported. Qublan et al.  in 2002 removed a 6 kg ovarian mucinous cyst after caesarean section. Petros et al.  removed a 30 × 25 mm bilateral mucinous benign ovarian cyst in 2005. As for Noreen et al. , in 2011, they reported a giant ovarian cyst discovered at 32 weeks of gestation and which was removed at 38 weeks of gestation through an oophorectomy. In 2017 Baradwan et al.  removed a 16.5 × 26.3 × 22.4 cm ovarian serous cystadenoma laparoscopically in the postpartum. All these cysts in the gravid-puerperium period did not have the size of our cyst, which measured 42 cm long-axis and weighed 19.7 kg. Except its large size, the cyst in our patient had no other malignancy. Worth noting is that, ultrasound features that increase the suspicion of malignancy are loss of any normal ovarian tissue surrounding the cyst and the existence of solid areas or papillary projections within the cyst. However, borderline tumors can be difficult to differentiate from benign tumors on the basis of ultrasound image characteristics.
Most cysts in the gravid-puerperium period are functional and therefore benign. It is often a luteoma of pregnancy. The other ovarian cysts encountered during pregnancy are, in order of frequency, benign teratomas, mucosal adenomas, rete ovarii tumors and endometriotic cysts . A serous cystadenoma is a commonest benign ovarian cyst and accounts for approximately 60–75% of ovarian cysts. They are the benign epithelial tumors and are usually unilateral and uni-locular. Their incidence tends to peak at 20–40 years. But the aetiology of serous cysts is unknow, although they may be associated with other ovarian tumors such as mature cystic teratomas. Cheng et al.  demonstrated that mutations in BRAF and KRAS that characterize serous borderline tumors and low-grade serous carcinomas are absent in serous cystadenomas. They speculated that a small proportion of these cystadenomas become clonal and that mutations of KRAS or BRAF in some of these clonal cystadenomas lead to the development of serous borderline tumors, which are the precursors of low-grad serous carcinoma.
After surgery, because our patient’s cyst was benign, the long-term risks were supposed to be very reduced. Those risks are related to surgery rather than pathology. Indeed, it can be argued that the occurrence of adhesions of intra-abdominal organs is possible after surgery. Also, the ovariectomy performed may slightly reduce fertility and decrease the age of onset of menopause.
This case report proves that vaginal delivery is possible in the association of giant ovarian cyst and pregnancy. Surgical management of a giant cyst was performed in the postpartum with satisfaction. This cyst, histologically, was known as benign. Indeed, for early diagnosis, a better evaluation through both clinical and systematic ultrasound, during antenatal period and intrapartum, should be encouraged even in low-resource countries.