Table 1 Measurements to assess the status of advanced maternal age and their effect on perinatal outcomes in Arba Minch zuria, and Gacho Baba district, southern Ethiopia, 2018/9

 Gestational age

A period counted from the Last Normal Menstrual Period (LNMP) if the mother remembered, or based on Ultrasound result during pregnancy.

Neonate’s gestational age categorized as pre-term for less than 37 weeks coded as “1”, a term for 37–42 weeks coded as “2′, and post-term 42+ weeks coded as “3″.

 Size of the neonate

Birth weight or size of the neonate during delivery.

The size of the neonate categorized as very small coded as “1”, smaller than usual coded as “2”, about average coded as “3”, and larger than usual coded as “4”.

 Stillbirth

Give birth to a dead fetus after 28 weeks of gestation.

Those conceptuses ended up with stillbirth coded as “1′, and the other coded as “2″.

 Neonatal mortality

Neonates died within 28 days of birth.

Those neonates died within 28 days by the non-accident case were coded as “1”, not were coded as “2”.

 Advanced maternal age

Defined as a pregnant mother aged ≥35 years old [17].

Categorized into two groups, and for the mother aged 20–34 years old was coded as “1” and “2” for ≥35 years.

 Parity

Number of births that the woman have

The responses categorized into two categories as primi (1st birth order) coded as “1” and multipara (2 or more birth order coded as “2”.

 BMI

Weight of women in kg per height square

Classified into underweight

(< 18.5 kg/m2), normal (18.5–24.9 kg/m2), overweight (25–29.9 kg/m2), obese (30–34.9 kg/m2), and morbidly obese (≥35 kg/m2).

 Wealth index

The EDHS household assets questions used, and principal component analysis done to rank the categories.

It ranked into three categories, 1st quantile coded as 1, 2nd quantile coded as “2”, and 3rd quantile coded as “3”.

 Distance to the health center

Approximate distance to the health center on foot which was responded by the respondent

Categorized in to two: “1” = ≤2 h on foot and “2”= > 2 h (BEmOC)

 Distance to the hospital

Approximate distance to the hospital on foot which was responded by the respondent

Categorized in to two: “1” = ≤2 h on foot and “2”= > 2 h (CEmOC)

 Household food insecurity

Both physical and economic access to sufficient food to meet their dietary needs for a productive and healthy life

Categorized households into four levels of household food insecurity (access) based on response to nine questions of HFIAS: food secure (1) and mild (2), moderately (3), and severely food insecure (4) [31].

 Districts (woreda)

 Kebele (wards)