A study published in the journal of the American Society of Plastic Surgeons revealed that combined oral contraceptives (COCs) containing both estrogen and progestin do not contribute to the development of enlarged breasts (macromastia), nor do they increase the risk of breast regrowth in adolescents and young women following breast-reduction surgery.

Despite the positive effects of COCs, Dr. Brian I. Labow of Boston Children′s Hospital and Harvard Medical School stated that many patients, parents, and clinicians are concerned that COC use will increase breast hypertrophy in teenagers. Hence, they conducted a study to determine the genuine influence of COCs on breast enlargement and symptoms in young women and girls.

The study included 378 patients who had previously undergone reduction mammaplasty surgery at Boston Children′s Hospital. Among these participants, the severity of macromastia was compared with one group using COCs and other HCs, as well as breast regrowth in the first year after surgery.

The findings of the study showed that patients who had macromastia were more likely to be overweight or obese, which was consistent with the idea that obesity is a risk factor for macromastia. Overall, only 5% of individuals experienced postoperative breast regrowth. Approximately half of the cases were caused by breast gland regrowth rather than weight gain. Women who took COCs following reduction mammaplasty likewise had no higher risk of breast regrowth. (Source: https://theprint.in/health/in-young-women-combined-oral-contraceptives-dont-raise-risk-of-macromastia-research/1148713/ )