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.