查看文章

Nulliparity is associated with lower birthweight, but few studies have examined how within‐mother changes in risk factors impact this association.

We used longitudinal electronic medical record data from a hospital‐based cohort of consecutive singleton live births from 2002–2010 in Utah. To reduce bias from unobserved pregnancies, primary analyses were limited to 9484 women who entered nulliparous from 2002–2004, with 23 380 pregnancies up to parity 3. Unrestricted secondary analyses used 101 225 pregnancies from 45 212 women with pregnancies up to parity 7. We calculated gestational age and sex‐specific birthweight z‐scores with nulliparas as the reference. Using linear mixed models, we estimated birthweight z‐score by parity adjusting for pregnancy‐specific sociodemographics, smoking, alcohol, prepregnancy body mass index, gestational weight gain, and medical …