Hengxi Chen, Jing Fu, Wei Huang

Hyperprolactinemia is the presence of abnormally high circulating levels of prolactin. Idopathic hyperprolactinemia is the term used when no cause of prolactin hypersecretion can be identified and it is causally related to the development of miscarriage in pregnant women, especially women who have a history of recurrent miscarriage. A possible mechanism is that high levels of prolactin affect the function of the ovaries, resulting in a luteal phase defect and miscarriage. A dopamine agonist is a compound with high efficacy in lowering prolactin levels and restoring gonadal function. To assess the effectiveness and safety of different types of dopamine agonists in preventing future miscarriage given to women with idiopathic hyperprolactinemia and a history of recurrent miscarriage. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 June 2016) and reference lists of retrieved studies. Randomized controlled trials (RCTs) in all languages examining the effect of dopamine agonists on preventing future miscarriage. Women who had idiopathic hyperprolactinemia with a history of recurrent miscarriages were eligible for inclusion in this review. Comparisons planned included: dopamine agonists alone versus placebo/no treatment; and dopamine agonists combined with other therapy versus other therapy alone. Two review authors independently assessed a single trial for inclusion, evaluated trial quality and extracted data. Data were checked for accuracy. One study (recruiting 48 women with idiopathic hyperprolactinemia) met our inclusion criteria; 46 women (42 pregnancies - 4/46 women did not conceive during the study period) were included in the analysis. The study compared the use of a dopamine agonist (bromocriptine, 2.5 mg to 5.0 mg/day until the end of the ninth week of gestation) versus a no-treatment control. The study was judged as being at a high risk of bias. It was not possible to carry out meta-analysis due to insufficient data.The study reported both of this review's primary outcomes of miscarriage and live birth. Results from this single study suggest that, compared to no treatment, oral bromocriptine was effective in preventing future miscarriage (risk ratio (RR) 0.28, 95% confidence interval (CI) 0.09 to 0.87, 46 participants (low-quality evidence)) in women with idiopathic hyperprolactinemia. There was no clear difference with regard to the other primary outcome of live births (RR 1.50, 95% CI 0.93 to 2.42, 46 participants (very low-quality evidence)).There was no difference with regard to this review's secondary outcome of conception (RR 0.92, 95% CI 0.77 to 1.09, 46 participants (very low-quality evidence)) between the group of women who received dopamine (21 out of 24 women conceived) and women in the no-treatment group (21 out of 22 women conceived). The included study only reported the serum prolactin levels in pregnant women and therefore the data could not be analyzed in this review. No other secondary outcomes relevant to this review were reported; adverse effects for women (nausea, vomiting, headache, vertigo, fatigue, hypotension, arrhythmia, and psychotic symptoms) and infants (birth defects, low birthweight, and developmental disabilities) were not reported.We downgraded the quality of the evidence for risk of bias in the one trial contributing outcome data (no description of allocation concealment, lack of blinding and possible reporting bias) and for imprecision (all effect estimates were based on small sample size, miscarriage was based on few events, and the 95% CIs of live birth and conception cross the line of no effect). Currently, there is insufficient evidence (from a single randomized trial with a small sample size, and judged to be at high risk of bias) to evaluate the effectiveness of dopamine agonists for preventing future miscarriage in women with idiopathic hyperprolactinemia and a history of recurrent miscarriage. We assessed outcomes using GRADE methodology. Miscarriage was assessed as low quality due to risk of bias concerns in the one trial contributing data (no description of allocation concealment, lack of blinding and possible reporting bias) and to imprecision (effect estimates were based on small sample size and few events). Live births and conception were assessed as of very low quality due to the same risk of bias concerns in study design and to imprecision (with a wide 95% CI consistent with either benefit or harm), and a small sample size. There were no data relating to adverse effects of the intervention for either the mother or her baby.Futher high-quality research in this area is warranted. There is a need for well-designed, larger RCTs to confirm and extend the findings of the trial reviewed here. Many questions remain unanswered. Some important considerations for future research include, the need for well-designed RCTs with large sample sizes, and for those studies to consider important outcomes (including adverse effects for both the mother and her baby). Future studies should examine the effectiveness and safety of various dopamine agonists including bromocriptine, cabergoline and quinagolide.