Hypertensive disorders of pregnancy after multifetal pregnancy reduction: a systematic review and meta-analysis

To systematically review the literature on hypertensive disorders of pregnancy (HDP) after multifetal pregnancy reduction (MFPR). A comprehensive search in PubMed, Embase, Web of Science, and Scopus was performed. Prospective or retrospective studies reporting on MFPR from triplet or higher-order to twin compared to ongoing (i.e., non-reduced) triplets and/or twins were included. A meta-analysis of the primary outcome HDP was carried out using a random-effects model. Subgroup analyses of gestational hypertension (GH) and preeclampsia (PE) were performed. Risk of bias was assessed using the Newcastle-Ottawa Quality Assessment Scale. Thirty studies with a total of 9,811 women were included. MFPR from triplet to twin was associated with a lower risk for HDP compared to ongoing triplets (OR 0.55, 95% CI, 0.37-0.83; p = 0.004). In a subgroup analysis, the decreased risk of HDP was driven by GH, and PE was no longer significant (OR 0.34, 95% CI, 0.17-0.70; p = 0.004 and OR 0.64, 95% CI, 0.38-1.09; p = 0.10, respectively). HDP was also significantly lower after MFPR from all higher-order (including triplets) to twin compared to ongoing triplets (OR 0.55, 95% CI, 0.38-0.79; p = 0.001). In a subgroup analysis, the decreased risk of HDP was driven by PE, and GH was no longer significant (OR 0.55, 95% CI 0.32-0.92; p = 0.02 and OR 0.55, 95% CI 0.28-1.06; p = 0.08, respectively). No significant differences in HDP were found in MFPR from triplet or higher-order to twin versus ongoing twins. MFPR in women with triplet and higher-order multifetal pregnancies decreases the risk of HDP. Twelve women should undergo MFPR to prevent one event of HDP. These data can be used in the decision-making process of MFPR, in which the individual risk factors of HDP can be taken into account.