Parity and low birth weight and preterm birth: a systematic review and meta-analyses

Objective. To systematically review the risks of pregnancy outcomes among women of different parity. Material and methods. Electronic databases were searched for studies, in English language, in which primary objective was to assess association between parity and pregnancy outcomes. Meta-analyses were performed and unadjusted odds ratios (ORs) and mean differences along with 95% confidence interval (CI) were calculated. Main outcome measures. Low birth weight (LBW), preterm birth (PTB), small for gestational age (SGA), birth weight, and gestational age. Results. Forty-one studies, most with moderate risk of bias were included. Nulliparity was associated with increased unadjusted odds of LBW (OR 1.41, 95% CI 1.26, 1.58) and SGA (OR 1.89, 95% CI 1.82, 1.96) and reduction in birth weight (weighted mean difference -282 g, 95% CI -486, -79 g) but not PTB (OR 1.13, 95% CI 0.96, 1.34). Grand multiparity and great grand multiparity were not associated with LBW (OR 1.10, 95% CI 0.95, 1.32 and OR 0.92, 95% CI 0.78, 1.09) or PTB (OR 0.96, 95% CI 0.77, 1.19 and OR 1.32, 95% CI 0.61, 2.83). Conclusions. Nulliparity was associated with a significantly increased unadjusted risk of LBW/SGA birth, whereas grand multiparity and great grand multiparity were not associated with increased risk of pregnancy outcomes.