| Value | Category | 
                                    
                    
                        | 0 | Single birth | 
                                    
                    
                        | 1 | 1st of multiple | 
                                    
                    
                        | 2 | 2nd of multiple | 
                                    
                    
                        | 3 | 3rd of multiple | 
                                    
                    
                        | 4 | 4th of multiple | 
                                    
                    
                        | 5 | 5th of multiple | 
                            
            Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.