Ovarian Tumours and Fibroids in Pregnancy

The apparent incidence of adnexal masses in pregnancy is increasing with the widespread and expanding use of antenatal ultrasound.¹
The majority of such masses do not cause problems and most are probably cysts of the corpus luteum that have not undergone full involution. They largely resolve by the second trimester of pregnancy.¹
Persisting adnexal masses are at risk of complications and may rarely require emergency or elective surgical resection (the optimal surgical window being ~16 to 20 weeks of gestation).¹
There is a small (~5%) risk of cancer in persisting ovarian masses.¹

Benign

• Functional ovarian cysts e.g. corpus luteum cysts
• Benign cystic teratomas
• Serous or mucinous cystadenomas
• Fibromas

Malignant

All rare and usually low-stage/low-grade:^2,3

• Germ cell tumours
• Borderline ovarian tumours
• Epithelial tumours
• Sex-cord stromal tumours

It appears that there is an increased risk of pregnancy loss associated with the presence of uterine fibroids in early pregnancy, especially with multiple fibroids.⁴One recent review suggest that fibroids are probably commoner than thought in pregnancy, but cause fewer problems:⁵

• One longitudinal study found a complication rate of 4 in 72 affected pregnancies.⁶
• There is a generally held misconception that fibroids usually increase in size during pregnancy but longitudinal studies have shown that this is not so.^5,6
• If they do enlarge, it is usually during early pregnancy.⁵

• The incidence of either fibroids or ovarian masses/tumours during pregnancy is difficult to estimate as there have been no rigorous population-based studies with agreed criteria.
• Fibroids appear to be relatively common but their exact prevalence is not defined and probably largely dependent on the type of population surveyed.
• Clinically detectable ovarian masses are thought to affect about 1 in 1500 pregnancies.
• Ultrasound scanning probably detects prevalence of adnexal masses in early pregnancy of about 1 in 200.
• The vast majority of these adnexal masses do not persist beyond the second trimester.
• Ovarian malignancy is very rare at ~7 cases per 10,000 pregnancies in one series.³

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. If either problem causes complications (see list below in complications section) they may present through the symptoms caused by this.

• For ovarian tumours the main question to consider is whether or not the tumour is benign/malignant.
• Uterine fibroids, once investigated by ultrasound scanning are unlikely to be confused with other pathologies.

• The main investigation of choice for uterine or ovarian masses in pregnancy is detailed ultrasound scanning.⁷
• This indicates the size, location, appearance and likelihood of any problems, to help decide on future management.
• Morphologic criteria can identify benign cysts compared with malignant tumours relatively accurately in the case of ovarian masses.
• For ovarian masses tumour markers are used mainly to monitor disease status during treatment, rather than as a diagnostic test due to a lack of specificity. Several markers can be elevated due to pregnancy itself e.g. CA125, beta-hCG.^2,8
• In confirmed malignancy where active treatment is considered, investigations to completely stage the tumour such as CT/MRI of pelvis may be used as risk to mother considered to outweigh that to fetus.¹

Ovarian masses

• If the tumour is thought to be benign and unlikely to cause complications, expectant management with follow-up scans is the norm.
• There is no clear evidence to support the routine laparoscopic excision of presumed benign ovarian tumours.⁹
• Surgery is indicated for large and/or symptomatic tumours and those that appear highly suspicious for malignancy on imaging tests.²
• The extent of surgery is decided by the intraoperative findings showing whether tumour is benign/malignant.²
• Conservative surgery is conducted for benign masses/borderline ovarian tumours.²
• More extensive surgery (including staging biopsies) for confirmed higher-grade malignancies.²
• Rarely chemotherapy may be given in 2nd/3rd trimesters, where the risk to mother outweighs that to the fetus;^2,3 short to medium-term fetal outcome appears to be relatively good.¹⁰

Uterine fibroids⁵

• Most fibroids cause no problems during pregnancy and are usually simply observed.
• Large submucosal and retro-placental fibroids have a higher risk of complications and may be operated upon, depending on perceived risk.^11,12
• Intractable fibroid pain unresponsive to medical treatments is an indication for myomectomy.
• Fibroids normally operated upon in first or second trimester unless emergency indication.
• Myomectomy should not be carried out at time of caesarean section except in emergency as there is a high morbidity due to haemorrhage.

Ovarian tumours¹

• Torsion presenting as acute abdomen¹³
• Rupture presenting as acute abdomen
• Obstruction of labour
• Pre-term labour
• Malignant transformation causing peritoneal spread (may lead to ascites and peripheral oedema)

Uterine fibroids⁵

• Large submucosal and retro-placental fibroids have greatest risk of complications
• Red degeneration due to hypoperfusion – acute abdominal pain
• Otherwise unexplained vaginal bleeding
• Placental abruption
• Intra-uterine growth retardation
• Pre-term labour
• Post-partum haemorrhage
• Malpresentation (rare)
• Obstructed labour (rare)

• Outcome is very good for the overwhelming majority of patients with fibroids and ovarian masses during pregnancy.
• Where intervention for fibroids is needed outlook is usually good, especially for elective surgery.¹⁴
• Prognosis in cases of ovarian malignancy is related to tumour-grade and stage, but one series shows 70% maternal survival and relatively good fetal outcomes.³
• Earlier diagnosis gives a better prognosis for ovarian tumours.³
• Grave prognosis associated with presence of ascites.³