Study setting, period and design
This community-based prospective cohort study conducted in the nine kebeles of Arba Minch zuria, and Gacho Baba districts included under Arba Minch-Health and Demographic Surveillance System sites (AM-HDSS) from October 15, 2018, to September 30, 2019. Arba Minch, the capital of the Gamo zone, is 505 km south of Addis Ababa and 275 km southwest of Hawassa, the capital city of the region. The total population of the districts has 164,529, of whom 82,199 are men and 82,330 women based on the 2007 central statistical agency (CSA) report. Arba Minch zuria, and Gacho Baba district have a total of 31 kebeles with three different climatic zones, high land, midland, and lowland, among which 9 kebeles are used as HDSS. The report of AM-HDSS showed the surveillance site has a total population of 74, 157.
Population
All women who were pregnant in Arba Minch zuria, and Gacho Baba district, AM-HDSS site from 2018–2019 were source as well as study population for this study.
Inclusion criteria
At enrollment for this study, all women who were pregnant and inhabitants to a minimum of six months in the study area were eligible for this study. The eligibility was defined by the pregnancy screening checklist which was developed by Whiteman et al.[26].
Exclusion criteria
During recruitment, all women whose ages less than twenty years old and known to be preexisting illnesses were excluded.
Sample size determination
The separate sample size was calculated in Epi info7 software Stat Calc for each specific objective. To determine the sample size for the first objective (to assess the status of advanced maternal age among pregnant women in Arba Minch zuria, and Gacho Baba district, southern Ethiopia, 2018/9) single population proportion was used by the following assumption: P = 0.334 from the study conducted in Norway[11], 95% level of confidence and 5% margin of error. Based on this, the estimated sample size was 342. To determine the sample size for the second objective (to determine the effect of advanced maternal age on obstetric outcomes among pregnant women in Arba Minch zuria, and Gacho Baba district, southern Ethiopia, 2018/9) two-sample comparison proportion was used. The assumption was P1 (age group 20–34) = 0.207 and P2 (age group ≥ 35) = 0.124 in one of the obstetric outcome (anemia) in advanced maternal age from the study conducted in Malaysia [14], 95%CI, ratio 1:1, and Power = 80% and the sample size estimated by this assumption was 676. The sample size for this study was estimated by adding a non-response rate of 10% to the larger sample size (sample size of the second objective). Therefore, the calculated sample size for this study was 744.
Data collection tool
The data were collected using a pretested interviewer-administered structured Open Data Kit (ODK) survey tool. The tools were developed by reviewing different works of literature. The questionnaire for wealth index indicators was adapted from Ethiopian Demographic Health Survey (EDHS) 2016[27] and included ownership of household assets and equipment, water supply, power supply, sanitary facility, residential homes, farmlands, and livestock ownership. The household food insecurity level was measured with Household Food Insecurity Access Scale (HFIAS), a structured, standardized, and validated tool that developed mainly by Food and Nutrition Technical Assistance (FANTA) [28]. The tool contains three main parts: Annex I (checklist to recruit the mothers to the study (background and pregnancy Information, and pregnancy screening checklist); Annex II (the tool to obtain baseline information); Annex III (tools for follow up survey to obtain obstetric outcomes) (Additional file 1).
Pretest
The tools were pretested in the Chencha district, which was out of study area to verify the appropriateness of the tool, and modifications and amendments were taken accordingly before actual data collection.
Data collection procedures
The well-trained nine data collectors and three field supervisors were prospectively identified obstetric outcomes among pregnant women during the study period. Intensive three days training gave for data collectors and supervisors separately regarding objectives of the study, and data collections ways. Data collectors discussed the information about the ODK survey tool and pregnancy screening checklists to identify pregnant women. As this was a community-based prospective follow-up study, data collected in different phases. In the first phase: all the baseline information about the women was obtained and pregnancy status was checked by using a pregnancy-screening checklist. After identified whether women were advanced age or not and the data collectors have recruited the women into the cohort of the study. The data were collected by home-to-home visits. In the second phase: the women were followed during pregnancy up to the immediate postpartum period to identify the obstetric outcomes. In the community setting the data collectors frequently contacted women or any household members, surround health care institutions, and health extension workers during the follow-up period.
Measurements
The description and measurements of the outcome and some of the explanatory variables were stated in detail below (Table 1).
Table 1
Measurements to assess the adverse obstetric outcomes at advanced maternal age in Arba Minch zuria, and Gacho Baba district, southern Ethiopia, 2018/9
Variables | Description | Measurements |
Outcome variables | | |
Obstetric outcomes |
Hypertensive disorder | Increased blood pressure above 140/90 mmHg during pregnancy with two measurements in 6 hours apart, and known by a health care professional during antenatal care, delivery, or postpartum period. | Those fulfilled the stated criteria were coded as “1”, not were coded as “2” |
Cesarean mode of delivery | Gave birth by the invasive procedure (incision is done on the abdomen, facia, and uterine wall. | Those fulfilled the stated criteria were coded as “1”, not were coded as “2” |
Hemorrhagic disorders | Any excessive vaginal bleeding after 28 weeks of gestation, and in the postpartum period. | Those fulfilled the stated criteria were coded as “1”, not were coded as “2” |
Miscarriage | Any termination of pregnancy for a non-medical reason before fetal viability (before 28 weeks of gestation) | Encountered women were coded as “1”, and not encountered were coded as “2” |
Prolonged labor | The mother stayed for more than 12 hours in labor after active onset. | Encountered women were coded as “1”, and not encountered were coded as “2” |
Premature rupture of membrane | Rupture of membrane before 18 hours of the onset of labor. | Encountered women were coded as “1”, and not encountered were coded as “2” |
Anemia | Maternal hemoglobin (Hb) < 10 g/dl, and signs like dizziness, blurred vision, and confirmed by a health professional and informed for the mother. | Women this condition were coded as “1”, and not encountered were coded as “2” |
Severe maternal morbidity | Severe disease condition during pregnancy, delivery, and postpartum periods like heart failure, renal failure, shock, and amniotic fluid embolism. | Women faced such type of conditions and treated as critical in the health care institution were coded as “1”, and not were coded as “2” |
Exposure variable |
Advanced maternal age | Pregnant mother aged ≥ 35 years old [7]. | Categorized into two groups and for the mother aged 20–34 years old coded as “1” and “2” for ≥ 35 years. |
Adjusted/confounding variable |
BMI | Wight 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 | Using EDHS household assets questions and principal component analysis will be done | 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”= ≤2hr on foot and “2”= >2hr (BEmOC) |
Distance to the hospital | Approximate distance to the hospital on foot which was responded by the respondent | Categorized in to two: “1”= ≤2hr on foot and “2”= >2hr (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)[28]. |
Data quality assurance
To ensure quality, experts translated questionnaires into the local language. A standard tool, which was commented by many experts, was used to collect the information. The data collectors and supervisors were trained to standardize and ensure consistency of data collection. The ODK survey tool that was very important to control the quality of data. The principal investigator and supervisors critically checked the data for completeness before uploaded to the ODK cloud server. Multiple imputation techniques were used for missed data that were not more than 20% of the needed information. Those study participants with inconsistent information were excluded from the final analysis. To maintain quality, the data were properly coded and categorized.
Data analysis and processing
The collected data downloaded from ODK aggregate and then exported to SPSS version 25 for analysis. Univariate analysis done in relation to maternal age. Principal Component Analysis (PCA) used to determine wealth quintiles. Bivariate and multivariable analysis done by using log-linear regressions. The assumptions for log-linear regression checked, and the goodness of fit-tested by the log-likelihood ratio (LR). All the variables with P ≤ 0.25 in the bivariate analysis included in the final model of multivariate analysis to adjust the confounding effect, and the variables selected by the backward stepwise technique. The model adjusted for educational and occupational status, party, wealth index, body mass index, household food insecurity access scale, habits, distance to health care institution, and sex of the neonate, antenatal care, postnatal care, and place of delivery to control the possible confounding effect. A standard error greater than two considered as suggestive of the existence of multi co-linearity. A crude and adjusted log-linear regression analysis done for each outcome variable with maternal age to estimate the beta coefficient (β). A statistically association declared at P-value < 0.05. Then the information presented by using simple frequencies, summary measures, tables, and figures.