Ovarian tumours and fibroids in pregnancy

Ovarian tumours and adnexal masses

The incidence of ovarian and adnexal masses in pregnancy appears to be increasing in line with the expanding use of antenatal ultrasound:¹

• The majority of such masses do not cause problems and most are functional cysts of the corpus luteum that have not undergone full involution. They usually resolve by the second trimester of pregnancy.

• Persisting adnexal masses can lead to complications and may (rarely) require emergency or elective surgical resection (the optimal surgical window being around 16 to 20 weeks of gestation).

Type of mass

Benign
Benign ovarian tumours are extremely common:

• Functional ovarian cysts.

• Benign cystic teratomas.

• Serous or mucinous cystadenomas.

• Fibromas.

Malignant
All ovarian cancers are rare and usually low-stage/low-grade:²

• Germ cell tumours.

• Borderline ovarian tumours.

• Epithelial tumours.

• Sex-cord stromal tumours.

Uterine fibroids (leiomyomata)³

As many as 10% of pregnant women have uterine fibroids. Most fibroids are small (< 5 cm) and remain stable in size. Although 30% of fibroids will increase in response to hormonal changes of pregnancy, most typically regress postpartum. Fibroids are usually asymptomatic, but complications increase with more and larger fibroids.

The most common complication is pain with degeneration. Pain occurs when a fibroid outgrows its blood supply, leading to ischemia. Women typically present with acute localised severe pain, usually in the first half of pregnancy, and typically require simple analgesia or opioids. Ultrasound may show fibroid degeneration, which does not harm the pregnancy.

Most fibroids do not affect fertility or increase miscarriage rate. Submucosal fibroids, which can distort the uterine cavity, are the least common subtype. They are first suspected when fibroids close to the endometrium are identified on transvaginal ultrasonography. After confirmation by sonohysterography, a referral to gynaecology is required, as submucosal fibroids have been associated with decreased rates of implantation and clinical pregnancy and increased rates of miscarriage.

A previous myomectomy may prompt caesarean delivery. After myomectomy, the incidence of uterine rupture in subsequent labour is low (less than 1%), regardless of whether vaginal or caesarean delivery is attempted. However, many obstetricians still suggest caesarean deliveries if substantial myometrium has been entered previously.

Vaginal delivery should be offered unless a large fibroid obstructs the cervix or leads to persistent fetal malpresentation. Complications at delivery include increased risk of breech presentation and postpartum hemorrhage. Ultrasound at term showing the presenting fetal part above the fibroid suggests a need for caesarean delivery. Fibroids may be removed at caesarean delivery (caesarean myomectomy) but this is not a primary indication for caesarean delivery.

How common are ovarian masses in pregnancy (epidemiology)?⁴

• The incidence of adnexal masses during pregnancy before 14 weeks of gestation varies from 6% to 25%. Most of these adnexal masses are functional ovarian cysts and generally resolve during pregnancy, leaving between 0.7% and 1.7% of women with persistent masses.

• The reported incidence of ovarian cancer in pregnancy ranges from 1 in 5000 to 1 in 47,000 live births, with 2% to 6% of persistent adnexal masses found to be malignant.

Presentation

• Most adnexal masses and fibroids are detected coincidentally during routine antenatal ultrasound.

• A small proportion of both pathologies may be large enough to detect clinically during bimanual palpation of the uterus.

• The mass may also cause complications (see list under 'Complications', below) and the patient then presents with symptoms caused by this.

Differential diagnosis

• For ovarian tumours, the main question is whether the tumour is benign or malignant.

• Uterine fibroids (once visualised by ultrasound scanning) are unlikely to be confused with other pathologies.

Investigations

The investigation of choice for uterine or ovarian masses in pregnancy is detailed ultrasound scanning including Doppler:⁵

• This indicates the size, location, appearance and likelihood of any problems, to assist decisions on management. Morphological criteria can identify benign ovarian cysts compared with malignant masses relatively accurately.

• Ovarian tumour markers are used mainly to monitor disease status during treatment, rather than as a diagnostic test, due to low specificity. Several markers can be elevated due to pregnancy itself - eg, CA 125, beta human chorionic gonadotrophin (beta-hCG) - and their use in pregnant cancer patients is not recommended.⁶

• In confirmed malignancy, investigations to stage the tumour, such as MRI scanning of the pelvis, may be used but CT and positron emission tomography (PET) should be avoided.⁶

Ovarian tumours and fibroids in pregnancy treatment and management

Ovarian masses

• If the mass is thought to be benign and unlikely to cause complications, expectant management and follow-up scans are recommended.

• Surgical management of adnexal masses during pregnancy appears to have favourable outcomes for the mother and the fetus.⁴

• There is little evidence to support the use of laparoscopic surgery in the management of presumed benign ovarian tumours.⁷

• Surgery after 15 weeks of gestation is indicated for large (greater than 5-10 cm in diameter) and/or symptomatic tumours and those that appear highly suspicious for malignancy (solid or mixed solid and cystic) on ultrasound.⁸

• Surgery should never be postponed, if deemed to be crucial, particularly once the time of 25 weeks of gestation has been reached.⁶

• The extent of surgery is decided by the intraoperative findings showing whether the tumour is benign/malignant:
  

  • Conservative surgery is indicated for benign masses/borderline ovarian tumours.

  • More extensive surgery (including staging biopsies) is indicated for confirmed higher-grade malignancies.

• Chemotherapy may be given from the second trimester of pregnancy but is associated with an increased risk of obstetric and fetal problems, including intrauterine growth restriction, premature labour and premature rupture of the membranes. Etoposide, used in the treatment of germ cell tumours, has been specifically associated with myelosuppression in the newborn.⁶

• The management of borderline ovarian tumours is generally difficult in younger women of reproductive age and is made more complex by pregnancy.⁹

Uterine fibroids

• Most fibroids cause no problems during pregnancy and observation is all that is required.¹⁰

• Diffuse uterine fibroids can be successfully treated conservatively to achieve a successful pregnancy outcome.¹¹

• Intractable fibroid pain unresponsive to medical treatments is an indication for myomectomy, as is a large fibroid (≥5 cm) located in the lower uterine segment.

• Fibroids are not normally operated upon in the first or second trimester other than in an emergency.

• Myomectomy should not normally be carried out at the time of caesarean section except in emergency, as there is a high morbidity due to haemorrhage, although there is emerging evidence that it can be a safe procedure for large (>5cm) myomas in carefully selected cases if performed by an experienced surgeon.¹² A Cochrane found only limited evidence that myomectomy improves subsequent fertility, which is the usual indication for myomectomy at the time of caesarean section.¹³

• Bilateral uterine artery embolisation (UAE) immediately after caesarean delivery may be effective in decreasing postpartum blood loss and minimising the risk of myomectomy or hysterectomy.¹⁴

Complications

Ovarian masses¹

• Torsion presenting as acute abdomen.

• Rupture presenting as acute abdomen.

• Obstruction of labour.

• Preterm labour.

• Malignant transformation causing peritoneal spread (may lead to ascites and peripheral oedema).

Uterine fibroids

Most women with fibroids have uneventful pregnancies; however, evidence does suggest an association with:¹⁵

• Red degeneration due to hypoperfusion - acute abdominal pain.¹⁶

• Otherwise unexplained vaginal bleeding.

• Placental abruption.

• Intrauterine growth restriction.

• Preterm labour.

• Postpartum haemorrhage.

• Malpresentation (rare).

• Obstructed labour (rare).

Large submucosal and retroplacental fibroids have the greatest risk of complications.¹⁰

Prognosis

The outcome is very good for the majority of patients with fibroids and ovarian masses during pregnancy.

• Elective surgery for an adnexal mass in the second trimester appears to be safe for both the woman and her baby.¹⁷

• Where surgical intervention for fibroids is needed, outlook is good, especially for elective surgery; there is, however, a higher caesarean section rate in women who undergo myomectomy during pregnancy, due to concerns over uterine rupture.¹⁵

• Prognosis in cases of ovarian malignancy is related to tumour histology and stage but one series shows 70% maternal survival and relatively good fetal outcomes:¹⁸
  

  • Earlier diagnosis gave a better prognosis.

  • A worse prognosis was associated with the presence of ascites.