A corpus luteum cyst in pregnancy is a fluid filled cyst that forms when the corpus luteum fails to regress and instead enlarges, usually to 3 to 5 cm. It makes progesterone that supports the pregnancy until the placenta takes over at about 10 to 12 weeks. It is the most common adnexal mass in early pregnancy and usually resolves by 14 to 16 weeks.

Risk factors: ovulation induction, assisted reproduction, multiple pregnancy, molar pregnancy.
Can rarely cause torsion or rupture.
Surgery is rarely needed.

Most women have no symptoms and the cyst is found at the first scan. Some have mild unilateral pelvic ache. Torsion or rupture cause sudden severe pain.

Cyst is mobile and tender if complicated.
Pulse and blood pressure are normal unless bleeding.
Differential diagnosis: ectopic pregnancy, ovarian torsion, haemorrhagic cyst, endometrioma, dermoid cyst, appendicitis.
Complications: torsion, rupture with haemoperitoneum, haemorrhage into the cyst, pain.

The principle is observation, because most cysts resolve without treatment.

Supportive: reassure; rest and avoid vigorous twisting; written warning symptoms; no removal of the cyst before 10 to 12 weeks because it supports the pregnancy.
Pharmacological: paracetamol 1 g oral 6-hourly as needed (maximum 4 g in 24 hours); micronised progesterone 400 mg vaginally twice daily only if the cyst is removed before 10 weeks.
Procedures: laparoscopic detorsion or cystectomy for torsion or rupture with instability.
Special groups: Rhesus negative women with bleeding or surgery give anti-D immunoglobulin 250 IU IM within 72 hours.
Red flags: sudden severe unilateral pain, vomiting, fainting, pulse above 100 per minute, falling haemoglobin.
Follow-up: repeat scan at 12 to 16 weeks to confirm resolution; if the cyst is above 5 cm or persists beyond 16 weeks, review again at 20 weeks; routine antenatal care.

Corpus Luteum Cyst in Pregnancy

Overview

Clinical Features

Diagnosis

Management