Simple ovarian cysts. Clinical features on a first-trimester ultrasound scan.

OBJECTIVE: To determine the clinical features of simple ovarian cysts, often seen on a first-trimester ultrasound scan. STUDY DESIGN: All initial examinations from patients scanned in 1993 and 1994 (N=1,001) were reviewed, and the clinical features of simple ovarian cysts were determined. Relationships were determined between the presence of a cyst and first-trimester pregnancy outcomes, including progression beyond the first trimester, blighted ovum, ectopic pregnancy and fetal demise. RESULTS: A simple ovarian cyst was observed in 29% of patients. Cysts were seen less often after 8 weeks' gestation, and there was an equal distribution between those on the right and those on the left side of the pelvis. Cyst diameters did not vary with gestational age, and most mean diameters were within a range of 1-3 cm. The absence ofa cyst was more often associated with a blighted ovum on follow-up ultrasound scan (relative risk, 2.8), but its presence or absence did not correlate with failure to progress beyond the first trimester, ectopic pregnancy or intrauterine fetal demise. CONCLUSION: The presence of simple ovarian cysts in the first trimester, which may represent corpus luteal cysts, appears to support early pregnancy development due to its association with a lower incidence of blighted ova.