Letter: Neural-tube defects and twinning.
D000757:Anencephaly / Q000453:epidemiology* / Q000401:mortality; D044383:Black People; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D011247:Pregnancy; D016135:Spinal Dysraphism / Q000453:epidemiology* / Q000401:mortality; D014427:Twins; D014481:United States; D044465:White People; D001741:Black or African American