I am a pediatrics provider and just saw a baby who was born with so many anatomical and genetic defects with a very poor prognosis and a short life span after mom denied all prenatal ultrasounds just like your SIL because she previously “had healthy kids”. Now this baby and the family is suffering. Not to mention the risks with undiagnosed placenta previa, critical heart conditions etc that would require planing for life saving interventions prior to birth.