Table 1 Definition and categories of variables used in the analysis into neonatal mortality rates in Sudan

Child sex

Male /female

Maternal age in years

Original variable present the mother’s age as continues variable. However, in the analysis mother’s age was entered as a categorical variable in which categorized into four age groups <20; 20–29; 30–39; ≥40 yrs.

Maternal education

Variable was constructed from two variables; 1st is ever attended school. Women who answered “yes” were asked the second about the highest level she completed. Women who reported that they only completed the preschool were considered as illiterate and added to women who reported in the first question that they have never attended school. Women who attended informal education such as “ illiterate eradication classes” are considered in the primary level and then they were added to the women who reported that they attended primary or intermediate levels (the basic education) Women who reported that they attended secondary or university levels were grouped together to be the third group. Categories were; illiterate, intermediate or less (≤8 years) and secondary or above (>8 years)

Area of residence

Rural/ urban

Household head education

Because of the very high percentage of missing in the education level variable, only ever vs. never had some education variable has been entered to the analysis as an indicator that lead us to know the role of education of head of household in any health decision taken. Illiterate / some education.

Household wealth index

The original variables has 5 categories ranged from poorest (the 1st quintile) to richest (the 5th quintile). Because of the very small numbers of neonatal deaths in the second and forth quintiles, the 2nd and the 1st quintiles were grouped together as well as the 4th and the 5th quintiles were grouped together. Therefore, the wealth index that used in the analysis contains three categories: poor, middle, and rich.

Parity

The original variable was continuous it was group in to three categories; primiparae, 2–4 children and multiparae ≥ 5.

Antenatal care utilization and delivery assistance

Were constructed from a multiple 9 alternative health providers. Women who answered: Traditional birth attendant or Community health worker, no one was coded as non / traditional health providers (THP) users. whereas women who answered doctor or nurse or village midwife or health visitor or medical assistant were coded professional health providers (PHP) users. However, if women mentioned that they visited both health provider belongs to THP group and one belongs to PHP group, they were considered as PHP users.

Ever had tetanus toxoid vaccination

Yes / No

Mode of delivery

The original variable has three categories: vaginal, Caesarean section, forceps extractor. Because of the very few cases in the forceps extractor, they were added to vaginal cases. Thus the variable that use in the analysis includes vaginal and Caesarean section

Place of delivery

Home/ health facility

Pregnancy complication and delivery complications

Women were asked about their personal experience in their last pregnancy and last delivery. The variables were constructed from the responses of the: excessive vaginal bleeding, high blood pressure, convulsions, high fever, foul smelling vaginal discharge, and Jaundice in which women who reported yes in at least one of these complications during pregnancy period / delivery were coded 1 “yes” whereas women who reported that did not experienced any of these complications were coded 0 “No”.