Effects of XXXX and maternal characteristics on perinatal outcomes: a population-based study using siblings.

@entity52 @entity1 @entity5958
OBJECTIVE: To study birthweight in consecutively born sibling singletons conceived with and without @entity52 ( @entity52 ) to disentangle the effects of maternal characteristics from those of the @entity52 treatment itself. DESIGN: Population-based study. SETTING: Not applicable. @entity1 (S): Firstborn and secondborn @entity1 from a 9-year birth cohort (1999-2007) comprising of 272,551 @entity1 who conceived two siblings. INTERVENTION(S): No intervention; @entity1 were conceived naturally or through @entity52 . MAIN OUTCOME MEASURE(S): Birthweight. RESULT(S): The study included 545,102 @entity1 born by natural conception (NC) or @entity52 with the data set obtained from the population-based Netherlands Perinatal Registry (PRN) containing information on pregnancies, deliveries, and neonatal outcomes. We used two approaches: [1] the intersibling approach and [2] the sibling-ship approach. In the first approach we included @entity1 born to four groups of mothers who conceived in the following order (numbers indicate birth order): NC1- @entity5958 (reference, n = 254,721), @entity5958 (n = 1342), NC1-IVF2 (n = 471), and IVF1-IVF2 (n = 687). Several comparisons were made to interpret the effects of @entity52 and maternal characteristics separately. In the second approach, perinatal outcomes of @entity52 @entity1 (n = 1,813) were compared with those of their NC siblings (n = 1,813). The intersibling analyses suggested an association between maternal characteristics and a lower birthweight, with estimates of the maternal effect ranging from -7  g (95% CI, -40; 26) to -101  g (95% CI, -170; -32). Neither the intersibling analyses nor the sibling-ship analyses indicated an additional adverse effect of @entity52 treatment itself. CONCLUSION(S): Maternal characteristics of subfertile @entity1 are associated with a lower birthweight. In  vitro fertilization treatment itself does not additionally contribute to a lower birthweight in the offspring.
