Introduction

Advanced aged mothers refer to those mothers aged 35 years or older during pregnancy or childbirth [1]. Globally, there is an observable trend of an increasing average age at childbearing [2, 3]. This shift is facilitated by the widespread adoption of assisted reproductive technology, extending to menopausal women through egg donor programs. Contributing factors to this trend include intentional delays due to career commitments, prolonged professional paths, postponed marriages, and the continuation of childbearing into later stages of life [4].

Pregnancies among advanced aged mothers are known to be associated with adverse maternal outcomes including obstructed labour, antepartum haemorrhage, postpartum haemorrhage, operative delivery, hypertensive disorders of pregnancy, [5,6,7]. Other adverse outcomes include preterm and post-term deliveries, anemia, premature rupture of membranes, multiple pregnancies, and maternal deaths [8,9,10,11].

Factors associated with adverse pregnancy outcomes among mothers of advanced age include chronic medical conditions such as diabetes and hypertensive disease, parity, socio-demographic factors such as maternal age, level of education and income and labor duration.[5, 11,12,13]. Maternal age has been independently associated with adverse outcomes with those beyond 40 years experiencing a higher impact [3, 10, 13].

In Southwestern Uganda, there is a gap in understanding maternal outcomes and associated factors among advanced-aged mothers, as no previous study has addressed this issue. The current study aims to fill this gap by laying the groundwork for evidence-based preventive interventions tailored to mothers in this age group. The findings do not only aim to improve outcomes, but also establish a framework for future research specific to this maternal demographic. Specifically, this study determined the prevalence of adverse maternal outcomes and associated factors among advanced-aged mothers receiving care at a tertiary hospital in southwestern Uganda.

Methods

Study setting, study design and study population

We conducted a cross sectional study at the Maternity Ward of Kabale Regional Referral Hospital (KRRH) in Southwestern Uganda. The hospital doubles as a teaching hospital for Kabale University School of Medical as well as a regional referral hospital for districts in southwestern Uganda and neighbouring countries of Democratic Republic of Congo and Rwanda. The Maternity Ward of the hospital conducts approximately 450 deliveries every month, with a caesarean section rate of 18–20%.

We included in our study all mothers aged 35 years and older during their immediate post-delivery period and before discharge who were admitted from March to August 2023.

Sample size and sampling methods

The sample size(n) was calculated using the Kish-Leslie formula [14] with a 5% significance level and 95% confidence level:

$${\text{n}}=\frac{({{\text{z}}}^{2}{\text{pq}})}{{{\text{d}}}^{2}}$$

where:

n is the total number of participants required.

z is the critical value (it is 1.96 at 0.05 level of significance).

p is the known proportion of pregnant women of advanced age (50% was considered due to lack of local prevalence data).

q is1-p.

d is margin of error (0.05).

n = 1.962 × 0.5x0.5/0.05.2

n = 384.

Accounting for a 10% non-response rate, a total sample size of 427 was obtained as shown below:

$${\text{N}}={\text{n}}/1-{\text{p}}$$
$${\text{N}}=384/0.9$$
$${\text{N}}=427$$

Data collection and study variables

Data were collected using interviewer administered structured questionnaires after obtaining written informed consent by four trained research assistants. These were midwives closely supervised by the principal investigator. We collected data on independent variables such as maternal socio-demographic, medical and obstetric characteristics and dependent variables were the adverse maternal outcomes. Socio-demographic variables included maternal age, education level, occupation, level of income, marital status and residence. Medical characteristics included pregestational diabetes, chronic hypertension, preexisting heart disease, and long-term medications. Obstetric variables included parity, duration of labour, history of contraceptive use, pregnancy-induced hypertension (eclampsia and pre-eclampsia) and antenatal care visits attendance.

Maternal adverse outcomes were obstructed labour, antepartum haemorrhage, mode of delivery (vacuum extraction or cesarean delivery), postpartum haemorrhage, hypertensive disorders of pregnancy, gestational age at delivery (preterm or postterm), anemia, premature rupture of membranes, multiple pregnancy, and maternal death. We defined adverse maternal outcomes as any of above complications sustained by the mother related to the most recent pregnancy, delivery and immediate post-partum events.

Data management and analysis

Data was entered in Epi Info software version 7 (CDC, Atlanta, USA) and exported to STATA version 15 (StataCorp, College Texas, USA) for analysis.

Maternal socio-demographic, obstetric, medical characteristics and fetal outcomes were summarized using descriptive statistics and expressed as frequencies/percentages. To determine the prevalence of adverse maternal outcomes, we calculated the percentage of participants experiencing any one of the complications related to pregnancy, delivery, and immediate post-partum events over the total study participants.

For both bivariate and multivariate analyses, we used a generalized linear model regression of the Poisson family with a log link (modified Poisson), with robust standard errors to identify factors associated with adverse outcomes among the study participants. This is because the prevalence of our outcome of interest was high [15, 16]. Variables meeting a significance threshold of p-value < 0.2 at bivariate analysis and those with biological plausibility, such as maternal age, were retained in the multivariable regression model. We reported prevalence ratios and their corresponding confidence intervals as measures of association. Significance for all analyses was set at p < 0.05.

Results

Out of 2,700 mothers who delivered during the study period of six months, 436(16.1%) were of advanced age. Three mothers declined consent to participate while other sixteen went home before completing questionnaires. We enrolled 417 women who were eligible to participate (Fig. 1).

Fig. 1
figure 1

Flow chart for recruitment of study participants

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Demographic, obstetric and medical characteristics of the study participants

Among the 417 participants, most fell within the age range of 35–37 years (49.4%), followed by those aged 38–40 years (36.9%), while only 13.7% were above 40 years old. Educational attainment was predominantly at the primary or secondary level (36.9% and 37.2%, respectively). A significant proportion were married (87.5%), resided in rural areas (65.7%), and were multiparous with five or more previous pregnancies (65.5%). The majority attended at least four antenatal care (ANC) visits (94%) and utilized contraception between pregnancies (77.9%). Chronic illnesses were reported in 3.3% of participants (Table 1).

Table 1 Demographic, obstetric and medical characteristics of the participants (N = 417)
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Prevalence of maternal outcomes

Of the 417 mothers who participated in the study, the majority (62.3%, n = 260) did not experience any adverse outcome. The prevalence of adverse maternal outcomes was 37.6% (n = 157, 95% CI: 33.1–42.4%) (Table 2).

Table 2 Maternal outcomes of study participants (N = 417)
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The most prevalent complication was obstructed labour, affecting 14.4% of participants. Other complications included anemia in pregnancy (4.5%), chorioamnionitis (4.1%), preterm prelabour rupture of membranes (3.9%), and chronic hypertension and preeclampsia (both 2.4%). One maternal death was recorded during the study period. In terms of delivery modes, the majority experienced spontaneous vaginal delivery (76.0%), followed by Caesarean Sect. (23.0%). Four delivered with vacuum assistance. Gestational age at delivery was primarily between 37 and 41 weeks (98.6%), with a small proportion occurring before 37 weeks (1.2%). Multiple pregnancies were identified in 3.1% of participants (Table 2).

Factors associated with adverse maternal outcomes

Participants who experienced precipitate labor < 3 h (adjusted prevalence ratio [aPR] = 1.95, 95% CI: 1.44–2.65), those that experienced prolonged labor lasting more than 12 h (aPR = 2.86, 95% CI: 1.48–3.16), and chronic hypertension (aPR = 2.01, 95% CI: 1.34–3.9) were more likely to experience adverse outcomes compared to their counterparts (Table 3).

Table 3 Factors associated with adverse maternal outcomes among mothers of advanced age at Kabale Regional Referral Hospital, southwestern Uganda
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Discussion

In this study, approximately two in five of the advanced aged mothers surveyed experienced at least one adverse maternal outcome. The most common adverse outcomes among these mothers were caesarian delivery and obstructed labour. Advanced aged mothers with prolonged labour, precipitate labour and chronic hypertension were more likely to experience adverse outcomes.

The overall rate of adverse maternal outcomes in the current study was 37.6%. This compares well with study findings from other countries such as 32.1% in Ethiopia [6], 36% in Israel [9, 17], 37.5% in Spain [18] and 36% in the USA[11]. However, the rate of adverse maternal outcomes in the current study was lower than the rates reported in Poland, Brazil, the USA, and Israel, where studies documented a higher proportion of mothers experiencing adverse outcomes ranging from 38 to 56% study [3, 19,20,21]. This divergence in adverse maternal outcome rates between our study and those in Poland, Brazil, the USA, and Israel can be attributed to the substantial inclusion of participants aged above 40 years in those studies. Advanced maternal age, especially beyond 40 years, is widely recognized as a significant risk factor for adverse outcomes, as corroborated by previous research [3]. Conversely, our study had a limited number of mothers aged 40 years or older, likely contributing to a lower proportion of adverse outcomes observed. Moreover, the comparatively favorable outcomes in our study may be attributed to several protective factors prevalent among our participants; the majority (94%) benefited from adequate antenatal care, minimizing potential complications. Additionally, the low prevalence of chronic medical morbidities among our study population and the widespread use of contraception likely contributed to the observed lower rate of adverse maternal outcomes compared to these studies. Furthermore, a significant proportion of our participants had achieved a fairly high level of education, which is consistently associated with improved maternal health outcomes[22].

The adverse maternal outcomes identified in our study were primarily obstructed labor (14.4%) and operative delivery (23%), alongside less frequent events such as PROM, antepartum hemorrhage, chorioamnionitis, preeclampsia, eclampsia, gestational diabetes, anemia in pregnancy, multiple pregnancies, and postpartum hemorrhage. These patterns in our findings are consistent with observations reported in other studies [2, 6, 9, 10, 13, 23].

In the current study, having prolonged or precipitate labour was associated with adverse outcomes among participants. Abnormal labour duration is consistently associated with maternal morbidities such as operative delivery, postpartum haemorrhage and sepsis [24]. Therefore, we recommend proper labor monitoring among advanced-aged mothers to avoid undue prolongation by intervening timely. In case these mothers experience precipitate labour, close and vigilant monitoring as well as prompt management of associated adverse outcomes should be considered as essential components of comprehensive care for this population.

In this study, having chronic hypertension was also associated with adverse maternal outcomes, consistent with other studies in the USA and the UK [25, 26]. This is because such mothers are faced with a high likelihood of elective operative delivery, gestational diabetes, and preeclampsia or eclampsia. On the basis of this finding, we recommend that advanced aged mothers with chronic hypertension be closely monitored during pregnancy, labour and delivery to avoid and or manage associated adverse outcomes.

This study is subject to certain limitations that merit acknowledgment. One notable constraint arises from the relatively modest sample size within the study group aged 40 years or older; restricting our statistical power to comprehensively assess the influence of very advanced maternal age on adverse perinatal outcomes. Women aged 40–44 years are known to be at more increased risk for adverse outcomes compared with women aged 35–39 years [23]. Additionally, the absence of a cohort of younger mothers for comparative analysis presents a limitation, as the entirety of our study participants were aged 35 years or older. Finally, our study findings are generalizable to advanced-aged women in the Southwestern Uganda region and similar peri-urban sub-Saharan African settings, and may not be generalizable to other study settings or populations. Despite these limitations, the primary strength of our study lies in its pioneering nature as one of the first investigations to explore adverse maternal outcomes among advanced-aged mothers in the East African Region.

Conclusion

Approximately two in five of the advanced-aged mothers surveyed had adverse outcomes. The most common adverse outcomes among these mothers are caesarian delivery and obstructed labour. Mothers with prolonged labour, precipitate labour and chronic hypertension are more likely to experience adverse outcomes compared to their counterparts. We recommend implementation of targeted interventions, emphasizing proper management of labor, close monitoring of advanced aged mothers, and a deliberate effort to avoid prolonged, to mitigate risks of adverse outcomes within this study population. In case of precipitate labour, such mothers should be closely monitored for adverse outcomes and timely interventions. Mothers conceiving or intending to conceive at advanced age should be counselled about likelihood of the adverse outcomes. Future longitudinal studies are recommended to better understand the immediate and long-term maternal outcomes associated with advanced maternal age in our setting.