Complex sentence: Assessing the risk for pregnancy complications at such an early time in pregnancy might give doctors the chance to reassure patients, and to prevent pre-eclampsia and premature birth, which are major contributors to maternal and neonatal morbidity and mortality.
Split into simpler sentences: Assessing the risk for those pegnancy complications at such an early time in pregnancy might give doctors, not just the chance to reassure patients, but also to prevent some of these complications (such as Pre-Eclampsia or Premature Birth). Those complications are major contributors to maternal and neonatal morbidity and mortality.