Subtle hyperprolactinaemia is not an uncommon finding in ovulatory subfertile women. The objective of this study is to evaluate the prevalence of hyperprolactinaemia in subfertile ovulatory and oligo-anovulatory women, and to determine if hyperprolactinaemia influences fertility treatment outcome. All women (n = 1010) who attended the fertility clinic of a UK tertiary hospital during 2015-2019 were included. Out of 804 eligible women analysed, 575 women (71.5%) were ovulatory and 229 (28.5%) were oligo-anovulatory. Prevalence of hyperprolactinaemia was higher in the ovulatory group than in the oligo-anovulatory group (26.8% vs. 14.4%; OR: 2.2; 95% confidence interval (CI): 1.4-3.2). On sub-group analysis, the prevalence of mild, moderate and severe hyperprolactinaemia was 23.0%, 3.7% and 0.2% in ovulatory women and 11.8%, 1.7% and 0.9% in oligo-anovulatory women. Mild hyperprolactinaemia was found to be more prevalent in the ovulatory group (OR: 2.2; 95%CI: 1.4-3.5). Ongoing pregnancy/livebirth rates were similar between hyperprolactinaemic and normoprolactinaemic women (42.8% vs. 46.7%). Hyperprolactinaemia did not have an impact on ongoing pregnancy/livebirth rates in both ovulatory and oligo-anovulatory women (OR:0.8; 95%CI: 0.5-1.1; OR: 1.2; 95%CI: 0.6-2.5, respectively). Hyperprolactinaemia is prevalent among ovulatory women, although most had mildly raised clinically insignificant levels. Elevated prolactin levels in ovulatory women do not seem to impact on pregnancy outcome. Impact StatementWhat is already known on this subject? Prolactin has been linked to ovulation and fertility. Prolactin testing is not generally recommended for subfertile women with regular menstrual cycles, which is a surrogate marker of ovulation. However, some clinicians, particularly in the general practice, still perform prolactin test as part of baseline endocrine profile.What do the results of this study add? Prevalence of hyperprolactinaemia in subfertile ovulatory women was 26.8% (154/575), of which 86% (132/154) were mild. Further, the livebirth/ongoing pregnancy rates were similar between hyperprolactinaemic and normoprolactinaemic women. Prolactin being a sensitive hormone, responsive to even minimal stress and its high levels not influencing clinical pregnancy outcome, prolactin measurement is not needed in women having regular menstrual cycles.What are the implications of these findings for clinical practice and/or further research? Hyperprolactinaemia was not uncommon in ovulatory women, although most had mildly elevated levels. Hyperprolactinaemia did not have any impact on fertility treatment outcome. Serum prolactin should not be tested in ovulating women, as mild elevations are commonly present and have no clinical significance.
Keywords: Prolactin; livebirth; ovulatory; pregnancy; subfertility.