Growth trend of small uterine fibroids and human chorionic gonadotropin serum levels in early pregnancy: an observational study

Objective: To analyze the growth trend of small uterine fibroids during early pregnancy, evaluating the potential factors involved, with particular interest in hCG levels.

Design: Observational study.

Setting: Tertiary care university hospital.

Patient(s): Women who had an ultrasound diagnosis of small myomas (diameter, ≥10 mm and ≤50 mm) from January 2007 to December 2013, and who subsequently became pregnant within 1 year.

Intervention(s): None.

Main outcome measure(s): Three additional ultrasound examinations were performed during early pregnancy (7-8, 10-13, and 20-22 complete gestational weeks, respectively) and the modifications in diameter and volume of each uterine fibroid were recorded. A serial evaluation of hCG serum levels from 5-12 weeks was performed.

Result(s): From the 109 women who fulfilled the study inclusion/exclusion criteria, a significant increase emerged, both for volume and diameter of the detected fibroids. Specifically, a median growth rate (GR) of 122% was observed during the interval of the first to the second ultrasound, whereas a median GR of 108% was detected during the interval between the second and the third ultrasound, and a median GR of 25% between the third and the fourth ultrasound. A significant positive correlation between hCG levels and diameter (R = 0.69) of myomas between 5 and 12 weeks emerged.

Conclusion(s): A remarkable nonlinear growth of small fibroids during initial pregnancy was observed, with a faster rate in the first trimester and a slowdown by midpregnancy. Those changes seem to be related to the similar increase of hCG levels until 12 weeks.