Clinical overview
Adnexal masses are found in approximately 1–4% of pregnancies, with the rate now higher because of routine first-trimester ultrasound. The clinical challenge is multifaceted: most are benign (functional cysts, corpus luteum, dermoid), a meaningful minority are persistent benign neoplasms requiring surgical consideration, and a small but important subset (~1–6% of masses persisting beyond 16 weeks) are malignant. The pregnant uterus distorts surgical access, complicates anaesthesia, and changes risk-benefit calculations for both observation and intervention. Add the time pressure of advancing gestation and the patient's understandable anxiety, and you have a high-stakes counselling and decision-making scenario.
The fundamental triage question is symptomatic or asymptomatic, simple or complex, persistent or resolving, and malignancy-suspicious or not. For symptomatic masses (the focus of this objective) the dominant concerns are acute torsion, haemorrhage into a cyst, rupture, infection of a tubo-ovarian collection adjacent to gravid uterus, and a degenerating endometrioma. Each trimester carries its own surgical and obstetric considerations.
A registrar must be able to (1) generate a trimester-aware differential, (2) safely investigate while protecting the pregnancy, (3) counsel on observation vs intervention, and (4) operate timing surgery — usually second trimester — to minimise risks to both mother and fetus.
Core knowledge
Differential by mass type
- Functional (corpus luteum) cyst. Persists until ~10–12 weeks, then regresses as placenta takes over progesterone production. Usually unilocular, thin-walled, <6 cm.
- Theca lutein cysts. Multilocular, often bilateral; associated with high β-hCG (GTD, multiple pregnancy, OHSS).
- Mature cystic teratoma (dermoid). Most common neoplastic mass in pregnancy. Pre-existing; presence of fat and calcifications on imaging.
- Serous cystadenoma. Usually unilocular, thin-walled.
- Mucinous cystadenoma. Multilocular, can become very large.
- Endometrioma. Pre-existing; may decidualise in pregnancy (can mimic malignancy on imaging).
- Hyperreactio luteinalis. Bilateral cysts from exaggerated response to hCG; commonly with GTD or twins.
- Pedunculated fibroid. Mimics adnexal mass; check origin from uterus.
- Heterotopic pregnancy — rare in spontaneous, ~1:100 in ART. Important not to miss; see ectopic-pregnancy-management.
- Malignancy — germ cell tumours (most common malignant in pregnancy because of young patient age — dysgerminoma, immature teratoma), borderline ovarian tumours, epithelial cancers, sex cord–stromal tumours.
Trimester-specific considerations
First trimester:
- Most masses are functional and will resolve by 16 weeks.
- Surgery rarely indicated unless severe symptoms (suspected torsion or rupture).
- Anaesthetic risk to embryogenesis (organogenesis 4–10 weeks); avoid teratogenic drugs.
- Risk of miscarriage from any surgery ~5–10%.
Second trimester (weeks 14–24):
- Surgical window of choice if intervention needed.
- Organogenesis complete; uterus still small enough to allow access; reduced miscarriage rate post-surgery (~1–3%).
- Persistence at 16 weeks is the key threshold for considering elective surgical management of a complex or large mass.
Third trimester:
- Surgery technically difficult; risk of preterm labour.
- Defer to postpartum unless urgent.
- Plan for delivery and consider concurrent surgery (e.g. cyst removal at caesarean if planned).
Symptoms and mechanisms
An enlarged ovarian cyst twists its pedicle lateral to the gravid uterus, producing acute unilateral pain and vomiting.
- Torsion — Acute severe unilateral pain, often with vomiting; risk highest at 8–16 weeks (rapid uterine growth shifting ovarian position) and immediately postpartum (uterine involution). See acute-pelvic-pain-pathophysiology for mechanism.
- Rupture — Sudden pain ± peritonism ± haemodynamic instability.
- Haemorrhage into cyst — Pain, palpable enlarging mass, anaemia signs.
- Infection — Less common; consider in immunocompromised, post-procedure.
- Pressure symptoms — Large masses → urinary frequency, constipation, dyspnoea.
- Decidualisation of endometrioma — Can present with bleeding into the lesion and concerning appearance.
Assessment
History
- Gestational age (LMP, EDD, dating scan).
- Pain onset, character, radiation, severity.
- Vaginal bleeding, discharge.
- Urinary, bowel, dyspneoa symptoms.
- Prior knowledge of ovarian pathology (pre-pregnancy scans).
- Fertility treatment, ART (heterotopic risk).
- Family history of ovarian/breast malignancy (BRCA).
- Personal cancer history.
Examination
- Vitals: shock from haemorrhage or rupture, fever from infection.
- Abdomen: tenderness, peritonism, palpable mass; remember the gravid uterus elevates other masses.
- Pelvic exam: only with caution if any concern for placental low-lying; check vaginal bleeding, cervical status, palpate mass via posterior fornix.
Investigations
Imaging.
- Transvaginal/transabdominal ultrasound — first-line. Document size, laterality, structure (unilocular cyst, multilocular cyst, solid component, papillary projections, vascularity), free fluid, and presence of an intrauterine pregnancy.
- Use IOTA criteria (simple rules / ADNEX model) where possible; performance maintained in pregnancy.
- MRI without gadolinium — safe in pregnancy after first trimester; superior for characterising indeterminate masses and assessing extra-pelvic disease without radiation exposure.
- CT — generally avoided; only if essential for non-gynaecological emergency (avoid in first trimester especially).
Tumour markers in pregnancy.
- CA-125: physiologically elevated in pregnancy (especially first trimester); peak around delivery; not reliable.
- AFP: elevated in pregnancy as a marker of fetal liver; not useful for ovarian malignancy.
- β-hCG: elevated by definition; not useful unless looking for GTD.
- LDH: useful for dysgerminoma if very high.
- HE4: not elevated by pregnancy (unlike CA-125) — can be useful.
- Inhibin B: useful for granulosa cell tumour.
The implication: tumour markers in pregnancy are interpreted with great caution. Imaging is dominant.
Other.
- FBC for anaemia.
- Group-and-save / cross-match for any surgical concern.
- Coagulation if significant bleeding.
Management
Observation
For asymptomatic women with simple, small (<5 cm) cysts: serial ultrasound at intervals (e.g. 12 weeks → 20 weeks). Most resolve. Avoid intervention.
For asymptomatic masses 5–10 cm, simple appearance: repeat scan at 14–16 weeks; consider second-trimester surgery if persisting.
Symptomatic management
Suspected torsion: urgent laparoscopy (or laparotomy if late pregnancy) with detorsion preserving the ovary; cystectomy of underlying lesion if feasible. See acute-pelvic-pain-management.
Acute rupture with haemodynamic instability: resuscitation + emergency surgery. Approach choice depends on gestation and surgeon experience.
Persistent symptomatic mass >5 cm: elective surgery in second trimester, with multidisciplinary input.
Surgical considerations
Approach:
- Laparoscopy is feasible up to ~24 weeks for experienced operators. Use open Hasson entry (avoid Veress in pregnancy); reduce pneumoperitoneum pressure (10–12 mmHg); left lateral tilt to avoid aortocaval compression.
- Laparotomy: usually low transverse incision; midline if very late pregnancy.
Anaesthesia:
- Avoid first trimester surgery if possible.
- Rapid sequence induction; protected airway; left lateral tilt; fetal heart auscultation pre- and post-op.
- Avoid teratogenic drugs (most modern anaesthetics safe).
Operative principles:
- Minimise uterine handling.
- Avoid spillage of cyst contents (especially if any concern of malignancy).
- Send all specimens for histology; intraoperative frozen section if suspicion of malignancy.
- Tocolysis is not routine; reserved for selected cases.
Postoperative:
- Fetal heart monitoring.
- VTE prophylaxis (pregnancy is prothrombotic).
- Adequate analgesia (paracetamol + opioids if needed; avoid NSAIDs after 30 weeks).
Malignancy in pregnancy
If frozen section or final histology confirms ovarian malignancy in pregnancy, multidisciplinary care with gynae-oncology is mandatory. Options depend on stage, histology, gestation, and patient preference:
- Conservative surgical staging (unilateral salpingo-oophorectomy, omental biopsy, peritoneal washings) for apparent stage I.
- Adjuvant chemotherapy can be administered safely after the first trimester (taxanes, platinum); fetal outcomes generally good when administered after 14 weeks.
- Plan delivery timing in consultation with neonatology, ideally after 34 weeks where possible.
- Definitive surgical staging completed postpartum.
Counselling
- Honest discussion of risk: most masses are benign; surgery in pregnancy carries small but real risks; observation is reasonable for many.
- Document discussions about: risk of miscarriage from surgery, risk of preterm labour, anaesthetic considerations, risk of malignancy.
- Involve partner; respect autonomy.
Red flags / pitfalls
- Anchoring on "functional cyst" beyond 16 weeks — persisting masses need full evaluation.
- Using CA-125 alone — unreliable in pregnancy.
- Forgetting heterotopic pregnancy in ART patients with an adnexal mass.
- Operating in first trimester for asymptomatic cysts — risk of miscarriage; defer if safe.
- Operating in third trimester when not absolutely necessary — preterm labour risk.
- Inadequate Veress in pregnancy — use open Hasson.
- Not considering decidualised endometrioma — can mimic malignancy on imaging.
- No fetal monitoring perioperatively — depending on viability, monitor fetal heart.
- Cyst spillage of a borderline tumour — increases recurrence risk; consider laparotomy if any concern.
- Failure to involve MDT for malignancy in pregnancy — gynae-oncology, MFM, neonatology, anaesthesia, psychology.
Evidence anchors
- RCOG Green-top Guideline No. 62 — Management of Suspected Ovarian Masses in Premenopausal Women.
- ACOG Practice Bulletin No. 174 — Evaluation and Management of Adnexal Masses.
- Schwartz N, et al. Adnexal masses in pregnancy: surgical and outcome data. Am J Obstet Gynecol.
- Mukhopadhyay A, Shinde A, Naik R. Ovarian cysts and cancers in pregnancy. Best Pract Res Clin Obstet Gynaecol.
- IOTA group: Timmerman D, et al. Simple ultrasound rules (Lancet Oncol 2008) and ADNEX model.
- ESGO/ESMO Consensus on the management of cancer during pregnancy.
- South African National Department of Health protocols for cancer in pregnancy.