Low birthweight prevalence among Spanish women during the economic crisis: differences by parity.

Previous studies have demonstrated a negative, significant impact on birthweight associated with the current economic crisis in Spain, which has also been reported for other European countries. Effects by parity are not known. Our aim is to compare the trends in low birthweight (LBW) by parity in Spain from 1996 to 2016. Using the National Vital Statistics data, joinpoint regression analysis was used to identify the time periods of significant changes in the prevalence of LBW by parity. Adjusted relative risk (RR) of LBW by year of birth was calculated in order to confirm that the time trend differences in LBW by parity were independent of possible confounders. The prevalence of LBW among live births to primiparous increased from 5.12% to 6.87% in 2008 and then stabilised at maximum values, while among live births to multiparous LBW increased from 3.96% to a maximum of 5.20% and then significantly reduced. Trends in adjusted RR of LBW by parity confirm that primiparous and multiparous were affected differently by the economic crisis. Older, nulliparous women may have felt more biosocial pressure to reproduce during the economic crisis, compared to women who were already mothers. This biosocial pressure may have increased the risks for LBW.