Explanation of variable:
    type of obstetrical problem
    
 
    Format of data:
     character: 
    - 1 = Preterm contractions 
    - 2 = Shortened cervix 
    - 3 = Preterm rupture of membranes 
    - 4 = Antepartum bleeding 
    - 5 = Intrauterine growth retardation (IUGR) 
    - 6 = Preeclampsia/HELLP 
    - 7 = Hypertension 
    - 8 = Gestational diabetes (unspecified type) 
    - 8.1 = Gestational diabetes (Diet) 
    - 8.2 = Gestational diabetes (Insulin) 
    - 9 = Placental abruption 
    - 10 = Placenta praevia 
    - 99 = Other, specify in PROB_S