Advanced maternal age pregnancy and its adverse obstetrical and perinatal outcomes in Ayder comprehensive specialized hospital, Northern Ethiopia, 2017: a comparative cross-sectional study

Advanced maternal age is usually defined as being 35 years or older which is believed to predispose mothers to enormous adverse outcomes during pregnancy [1]. A study done in 29 countries (Africa, Asia, Middle East, and Latin America) revealed that the magnitude of pregnant women with advanced maternal age was 12.3% [2]. A previous study conducted in the United States of America showed that the average age of women at first birth has consistently increased over the last four decades, with the birth rate for women aged 40–44 more than doubling from 1990 to 2012 [3]. A retrospective comparative study done in a South Africa tertiary hospital revealed that the prevalence of advanced maternal age was 17.5% [4].

Advanced maternal age is associated with various economic, social and health complications to the mother and to the fetus or neonate as well [2, 5]. Various studies conducted on the topic elucidated that the aftermath of advanced maternal age (AMA) is highly linked with the occurrence of pregnancy-induced hypertension, DM, maternal near-miss, increased cesarean delivery, malpresentation, and maternal death. Alongside with this, AMA also results in neonatal complications, such as Low Apgar score, NICU admission, preterm delivery, low birth weight, birth defects, chromosomal abnormalities and perinatal death [2, 4‐7].

Fertility in women starts to decline in the early thirties and even decreases faster after mid and late thirties. Women with advanced age usually have a relatively lower tendency to achieve pregnancy within a short period. The probability of achieving pregnancy in a single menstrual cycle, fecundability, is decreased in these age groups [8, 9].

Globally, the academic community has extensively explored the association of AMA with adverse obstetrical and perinatal outcomes. However, few researches have been conducted to identify the association of AMA with these outcomes in the study area and in Ethiopia. Hence, there is a need to carry out research to determine the magnitude of obstetrical and perinatal outcomes associated with AMA. On the other hand, identifying the outcomes of AMA pregnancy will be useful in designing effective sensitization programs for couples and empowering them about informed choices for pregnancies during advanced maternal age. Furthermore, the result of this study can be utilized by concerned bodies to optimize natal care given for advanced aged mothers.

A chart review retrospective comparative cross-sectional study was conducted from November 2017 to December 2017 to assess the association of advanced maternal age pregnancy with adverse obstetrical and perinatal outcomes in Ayder Comprehensive Specialized Hospital. The hospital is one of the biggest tertiary and teaching hospitals with a good reputation in the country. It is located in Mekelle city, 783 km north of Addis Ababa, the capital city of Ethiopia. The hospital has 500 beds and serves more than 17,000 patients every year. It is estimated that around 3000 women give birth annually in the hospital.

The sample size was calculated using Open Epi Data statistical software. A one to one ratio of study to reference group, 95% confidence level and power of 90% was assumed. Taking cesarean delivery rate among exposed which is 27 and 17% among non - exposed [10], it yielded a total sample size of 752 (376 charts of mothers whose age is > 35 years and 376 charts of mothers whose age is between 20 to 34 years). Charts of mothers who gave birth in Ayder Comprehensive Specialized Hospital from September 2015 to September 2017 which were selected using systematic sampling were reviewed in this study. Pregnant mothers whose age is ≥35 years were regarded as a study group and mothers whose age is between 20 and 34 years were taken as a reference group. Mothers with pre-existing medical disease, twin pregnancy, Rh negative mothers and incomplete records were excluded from the study.

Data were retrieved from the sampled mothers’ chart using a structured checklist which was developed after reviewing variables discussed in various literature to enable the researchers to collect data on socio-demographic status, obstetric history, mode of delivery, adverse obstetrical and perinatal outcomes.

Prior to the data collection, the checklist was reviewed by senior researchers for its validity. Four graduate midwives with previous experience in data collection were hired as data collectors and two MSc in Clinical Midwifery students were recruited as supervisors. Three days of training on data collection was provided. Ten percent of the collected data was checked by supervisors every day for its completeness and the principal investigator monitored the overall tasks. The checklist was pretested in 10% of the calculated sample size in the same hospital on charts of mothers who visited this hospital four years prior to the study period. After this pretest was undertaken, one outcome variable (NICU admission) and one explanatory variable (educational status) were omitted from the checklist.

The data were checked for completeness, then coded, entered, and analyzed using Statistical Package for Social Sciences (SPSS) version 20. Descriptive statistics were used to compute frequency, percentile, mean and median of different variables. A Binary regression model was employed to test the association between the dependent and independent variables. Dependent variables are adverse obstetrical outcomes such as PIH, APH, cesarean delivery, amniotic fluid disorders, PROM, GDM, and postpartum hemorrhage. Moreover, perinatal outcomes such as preterm delivery, low birth weight, low fifth minute Apgar score, post-term pregnancy, and perinatal death are dependent variables. Each adverse obstetrical outcome was assessed if it has made a significant association with maternal age, residence, gravidity, number of ANC visits, adverse obstetric history and malpresentation. On the other side, each perinatal outcome was tested to see its association with PIH, APH, amniotic fluid disorders & PROM, alongside with maternal age, residence, gravidity, number of ANC visits, bad obstetric history and malpresentation. All variables with P-value ≤0.25 were included in the multivariable analysis. The magnitude of the association was measured using odds ratio at 95% confidence interval and statistical significance was declared at P-value of ≤0.05.

This study has indicated that advanced maternal age is an important risk factor for many adverse obstetrical and perinatal outcomes. One of the main findings of this study was the association of maternal age with pregnancy-induced hypertension in which advanced age mothers were four times more likely to encounter pregnancy-induced hypertension than their adult counterparts (OR 4.15, (95% CI 2.272–7.575), p < 0.001). This result is congruent with the study done in Malaysia and UK with an odds ratio of 5 (AOR 5, 95% CI 1.95–12.65) and 1.5 (AOR, 1.49 (95% CI, 1.22–1.82); P < 0.001), respectively [10, 11]. Moreover, studies from Saudi Arabia and Turkey also stated that there was a statistically significant difference in the incidence of PIH between advanced aged and adult mothers [12, 13]. This similarity might be mainly attributed to the fact that endothelial response to vasodilators diminishes as mothers get older [14]. Nevertheless, a study conducted in India contradicts this study as it claimed that PIH has no significant association with maternal age [15]. This can be accounted for by the difference in sample size.

In addition, maternal age was found to be significantly associated with APH (OR 2.54 (95% CI 1.32–4.91), P = 0.005) in this study. This finding is supported by studies done in Amman Jordan [16]. This could be ascribed to increased gravidity in advanced age mothers which in turn make them at greater risk of having placenta Previa [14]. In contrast, studies from Turkey and India showed no significant association of maternal age with APH [12, 15]. This could be accounted for by differences in the setup of the study area as this study had been conducted in a tertiary hospital which mainly provides services to referral cases from the peripheral health institutions.

Another finding of this study was the association of maternal age with the mode of delivery. This study found that advanced age mothers were nearly 3 times more likely to have their babies born via cesarean section than their adult counterparts (OR 2.7, p < 0.001). This is in line with studies done in India (OR 2.4), Malaysia (OR 2.21) and UK (OR 1.95) [10, 11, 15]. This might be due to the fact that the proportion of malpresentation and bad obstetric history was higher in advanced aged mothers. On the other hand, mothers with bad obstetric history would rather undergo elective cesarean section because it is believed to be safer than vaginal delivery. Secondly, pregnancy complications, such as PIH and APH were commonly seen in advanced age mothers and that cesarean section could be considered for maternal reasons. Lastly, this could be due to the study area taking into consideration that this hospital is a teaching hospital for obstetrician cohorts.

In addition to these findings, this study also revealed that maternal age was not found to be a major risk factor for gestational DM, amniotic fluid disorders, PROM and PPH. However, studies from Malaysia, Saudi Arabia, the UK, and South Korea concluded that advanced maternal age was a major risk factor for gestational DM [10, 11, 13, 17]. This may be accounted for by differences in socio-economic status wherein pre-pregnancy body mass index could be affected. Paradoxically, a study in India also concluded that age was a major risk factor for PPH and amniotic fluid disorders. This could be attributed to a difference in sample size. However, this Indian study also claimed that age doesn’t have a significant association with PROM [15]. Similarly, a study in Jordan also stated that age was not found to be associated with PPH [16]. This similarity might be due to under-diagnosis of PPH.

This study affirmed that advanced maternal age is significantly associated with adverse obstetrical outcomes like pregnancy-induced hypertension and antepartum hemorrhage. Cesarean delivery was also tremendously increased in those mothers. On top of this, advanced maternal age pregnancy was also found to be a major risk factor for preterm delivery, low birth-weight, low fifth minute Apgar score and perinatal death. Therefore, it is better for health care providers to counsel couples, who seek to have a child in their later ages, about the risks of advanced maternal age pregnancy. In addition, health care workers need to give emphasis on how to improve advanced age mothers’ health through the utilization of contraception in order to reduce pregnancy in this age group.