Is Increasing Parity Associated with Adverse Perinatal Outcomes in Dichorionic Twin Gestations?

Objective Dichorionic twins have increased risk of preterm birth and hypertensive disorders of pregnancy. Grand multiparity may be associated with adverse perinatal outcomes in singleton pregnancies, although the effect of increasing parity in twins is unclear. This study aimed to elucidate whether grand multiparity leads to adverse outcomes in dichorionic twins compared with multiparity and nulliparity.Study Design This was a retrospective review of dichorionic twins at a single institution between January 2008 and December 2019 comparing pregnancy outcomes among grand multiparity, multiparity, and nulliparity. Primary outcome was preterm birth less than 37 weeks. Multivariable regression controlled for differing demographics, prior preterm birth, use of reproductive technologies, and hypertensive disorders of pregnancy. Chi square and Fisher's exact were used for categorical variables and Kruskal-Wallis was used for continuous variables.Results A total of 843 (60.3%) pregnancies were nulliparous, 499 (35.7%) multiparous, and 57(4.1%) grand multiparous. Univariate analysis indicated that multiparous women had lower incidence of preterm birth less than 37, 34, and 32 weeks (57 vs. 51%, p = 0.04; 19.2 vs. 14.0%, p = 0.02; 9.6 vs. 5.6%, p = 0.01) and that grand multiparous women had lower incidence of preterm birth less than 34 weeks (19.2 vs. 5.3%, p = 0.008) compared with nulliparous women. Multivariable regression confirmed multiparous women had lower odds of preterm birth less than 34 and 32 weeks compared with nulliparous women (<34 wk: odds ratio [OR] = 0.69, 95% confidence interval [CI] = 0.49-0.97, p = 0.03; <32 wk: OR = 0.48, 95% CI = 0.29-0.79, p = 0.004) and that multiparous women (OR = 0.57, 95% CI = 0.42-0.77, p = 0.0002) and grand multiparous women (OR = 0.23, 95% CI = 0.08-0.68, p = 0.0074) had lower incidence of hypertensive disorders of pregnancy when compared with nulliparous women.Conclusion Grand multiparity is not associated with adverse perinatal outcomes compared with nulliparity or multiparity in dichorionic twins. Increasing parity may protect against incidence of preterm birth and hypertensive disorders of pregnancy even among grand multiparous women.