A 37-year old pregnant patient, presented in the 36th week of pregnancy with progressive visual loss. Medical history revealed morbid obesity (BMI 46.5), and gestational diabetes for which she used insulin. At presentation she reported to have slowly progressive visual loss, without headache nor vomiting. She conceived spontaneously, and had regular periods prior to conception. Physical examination showed no abnormalities, expect a loss of visual acuity of the left eye of 0.04. The visual acuity for the right eye was 0.90. Visual field test showed bitemporal hemianopsia. A MRI scan was performed and showed a sellar mass suspect for a pituitary macroadenoma, with chiasmatic compression. Labarotory results showed a prolactin level of 6.6 IU/L, which is in accordance with expected prolactin levels in the third trimester of gestation. A high-dose hook effect was excluded with additional lab testing. Other pituitary functions appeared to be normal.  We concluded that our patient had a non-functioning pituitary adenoma. Cabergolin 0.5 mg per 2 days was started. Within one week after start of medical treatment, prolactin levels dropped to 0.76 IU/L, and visual acuity of the left eye improved to 0.3. Two weeks after start of treatment, patients gave birth to a healthy girl by vaginal delivery. One month later visual defects were fully recovered. Pituitary MRI showed shrinkage of the pituitary gland with disappearance of the chiasmatic compression.  

Discussion
Hyperplasia of the pituitary lactotroph cells in the presence of a non-functioning adenoma is a rare cause of visual loss during gestation. Women with a known pituitary adenoma should be counselled about potential growth of the lesion during pregnancy. We started medical treatment with cabergolin, to avoid transsphenoidal surgery in the third trimester of pregnancy. Cabergoline is usually preferred over bromocriptine during pregnancy because of its better efficacy with fewer adverse effects.