{"adequacy": "adequacy of care",
 "alcohol": "risk factor, alcohol use",
 "anemia": "risk factor, Anemia",
 "birattnd": "medical person attending birth",
 "birmon": "birth month Jan-Dec",
 "bord_0": "birth order of lighter twin",
 "bord_1": "birth order of heavier twin",
 "brstate": "state of residence NCHS",
 "brstate_reg": "US census region of brstate",
 "cardiac": "risk factor, Cardiac",
 "chyper": "risk factor, Hypertension, chronic",
 "cigar6": "num of cigarettes /day, quantiled",
 "crace": "race of child",
 "csex": "sex of child",
 "data_year": "year: 1989, 1990 or 1991",
 "dfageq": "octile age of father",
 "diabetes": "risk factor, Diabetes",
 "dlivord_min": "number of live births before twins",
 "dmar": "married",
 "drink5": "num of drinks /week, quantiled",
 "dtotord_min": "total number of births before twins",
 "eclamp": "risk factor, Eclampsia",
 "feduc6": "education category",
 "frace": "dad race",
 "gestat10": "gestation 10 categories",
 "hemo": "risk factor Hemoglobinopathy",
 "herpes": "risk factor, Herpes",
 "hydra": "risk factor Hvdramnios/Oliqohvdramnios",
 "incervix": "risk factor, Incompetent cervix",
 "infant_id_0": "infant id of lighter twin in original df",
 "infant_id_1": "infant id of heavier twin in original df",
 "lung": "risk factor, Lung",
 "mager8": "mom age",
 "meduc6": "mom education",
 "mplbir": "mom place of birth",
 "mplbir_reg": "US census region of mplbir",
 "mpre5": "trimester prenatal care begun, 4 is none",
 "mrace": "mom race",
 "nprevistq": "quintile number of prenatal visits",
 "orfath": "dad hispanic",
 "ormoth": "mom hispanic",
 "othermr": "risk factor, Other Medical Risk Factors",
 "phyper": "risk factor, Hypertension, preqnancy-associated",
 "pldel": "place of delivery",
 "pre4000": "risk factor, Previous infant 4000+ grams",
 "preterm": "risk factor, Previos pre-term or small",
 "renal": "risk factor, Renal disease",
 "rh": "risk factor, RH sensitization",
 "stoccfipb": "state of occurence FIPB",
 "stoccfipb_reg": "US census region of stoccfipb",
 "tobacco": "risk factor, tobacco use",
 "uterine": "risk factor, Uterine bleeding"}