Short inter-pregnancy interval (IPI), classically defined as less than 24 months between a live birth and conception of the subsequent pregnancy, is a key modifiable risk factor for adverse maternal and perinatal outcomes [1]. Inadequate recovery time between pregnancies has been associated with anemia, hypertensive disorders, postpartum hemorrhage (PPH), preterm birth, low birth weight, small-for-gestational-age neonates and increased perinatal mortality [2]. The World Health Organization (WHO) recommends waiting at least 24 months after a live birth before conceiving again, corresponding to a birth-to-birth interval of about 33 months [3]; USAID and other agencies further suggest that 3 - 5 years may provide optimal health benefits [4].

Globally, about one quarter of births occur after short IPIs, with the burden disproportionately borne by low- and middle-income countries [5]. In Sub Saharan Africa, estimates suggest that 20% - 59% of women experience short intervals between pregnancies, reflecting high fertility, limited access to contraception and social norms favoring closely spaced births [6]. In Ethiopia, recent hospital-based studies report short IPI prevalences around 40% - 45% and demonstrate strong links to low maternal education, high parity, suboptimal breastfeeding duration and non-use of modern contraception [7]. Similar patterns have been described in Tanzania and other African settings [8].

Cameroon faces persistently high maternal and neonatal mortality, estimated at 467 maternal deaths per 100,000 live births and 28 neonatal deaths per 1000 live births [9]. The 2018 Demographic and Health Survey reported a high total fertility rate of 4.8 children per woman and an unmet need for birth spacing of around 15% among married women aged 15 - 49 years, conditions that favor short IPIs [10]. The median birth interval in Cameroon is approximately 31.2 months, masking substantial heterogeneity between regions, urban and rural areas, and socio-economic strata [10].

Understanding determinants of short IPI and its consequences in urban referral settings can guide targeted interventions to improve maternal and perinatal outcomes. Several biological mechanisms have been proposed to explain the association between short IPIs and poor outcomes. The maternal depletion syndrome posits that closely spaced pregnancies do not allow sufficient time for restoration of maternal nutrient stores and physiological reserves, resulting in increased risks of anemia, hypertensive disorders and obstetric complications [11][12]. The folate depletion hypothesis suggests that inadequate replenishment of folate between pregnancies contributes to fetal growth restriction and preterm birth [13].

In addition to biological pathways, social and behavioral factors such as contraceptive non-use, unintended pregnancy, low decision making power, and limited knowledge of optimal birth spacing strongly influence the occurrence of short IPI [14]. Despite the public health relevance of birth spacing, there are limited contemporary data on short IPI, its determinants and outcomes among pregnant women in Cameroon, particularly in high volume urban facilities such as Douala Laquintinie Hospital (DLH) and Nylon District Hospital (NDH). Existing DHS data provide aggregate information on birth intervals but do not link them to detailed obstetric outcomes or women’s knowledge and practices around optimal spacing [10].

Given Cameroon’s high fertility and mortality indicators, and the documented benefits of optimal birth spacing, there is a pressing need for context-specific evidence to support postpartum family planning and counseling strategies [10][15]. Urban public hospitals in Douala serve large, socio-economically diverse populations and are critical platforms for interventions targeting women at high risk of closely spaced pregnancies [16]. Identifying modifiable determinants of short IPI and quantifying its contribution to adverse maternal and perinatal outcomes will help clinicians and policymakers design more effective birth spacing and contraceptive programs [17]. Assessing women’s knowledge of optimal IPI is equally important to tailor counseling messages and address misconceptions [18].

Generalobjective

To determine the prevalence, determinants and outcomes of short inter pregnancy intervals, and to assess knowledge of optimal birth spacing among women delivering at Douala Laquintinie Hospital and Nylon District Hospital in Douala, Cameroon.

Specificobjectives

1) To identify socio demographic and reproductive determinants of short inter pregnancy intervals in the two hospitals.

2) To determine maternal and perinatal outcomes associated with short inter pregnancy intervals in this population.

3) To assess the level of maternal knowledge regarding optimal birth spacing and inter pregnancy intervals among women attending maternity services in the study sites.

Studydesign

We conducted a hospital based cross sectional analytic study among women admitted for delivery at two public hospitals in Douala, Cameroon. The design enabled estimation of the prevalence of short IPI and assessment of associations with selected determinants and outcomes.

Studysetting

The study took place in the obstetrics and gynaecology units of Douala Laquintinie Hospital (DLH) and Nylon District Hospital (NDH) in Douala, the economic capital of Cameroon with an estimated population of about 3.9 million inhabitants. DLH is a second category referral hospital with a bed capacity of approximately 917 and serves as a major teaching facility for the Faculty of Medicine and Pharmaceutical Sciences, University of Douala. Its obstetrics and gynaecology department includes maternity, post-partum, post operative, pathological and non-pathological pregnancy care, and gynecological units staffed by eight obstetrician gynaecologists and roughly 30 nurses and midwives.

NDH is a first category district hospital serving a densely populated, lower income catchment area, with an obstetrics and gynaecology unit comprising maternity, post-partum and delivery room sub units staffed by three gynaecologists and about 18 nurses and midwives. Both facilities conduct a high volume of deliveries and provide routine antenatal, intrapartum and postnatal care as well as family planning services.

Studyperiodandduration

Data was collected prospectively over four months, from February to May 2022.

Studypopulation

The study population comprised pregnant women admitted for delivery at DLH and NDH during the study period who had at least one previous live birth within the preceding five years study inclusion window irrespective of route of delivery (vaginal or Caesarean).

Inclusioncriteria

Pregnant women with at least one prior live birth within the last five years.Admitted to deliver at DLH or NDH during the study period.Provided written or verbal informed consent.

Exclusioncriteria

Non consenting women.Women whose immediately preceding pregnancy ended in miscarriage or induced abortion.Women unable to recall the date of birth of their previous child.

Samplesizeandsampling

The minimum sample size was calculated using Cochran’s formula: n = z 2 p ( 1 − p ) / e 2 , assuming a standard normal deviate of 1.96 (95% confidence), a prevalence of short IPI of 40.9% based on an Ethiopian study by Mamo et al., and a margin of error of 5%. This yielded a sample size of 371, which was increased by 10% to account for non-response, giving a final target of 408 participants. A total of 450 women were screened to attain the sample size of 408.

A non-probability purposive sampling technique was used; eligible women were consecutively enrolled as they were admitted for delivery. The sample was allocated proportionally to the two hospitals based on their average monthly delivery volumes: approximately 100 at NDH and 180 at DLH. Thus, 146 women (35.8%) were recruited from NDH and 262 (64.2%) from DLH (Figure 1).

Figure 1. Flow diagram of participants.

Studyvariables

Exposure (predictor) variables

Socio demographic: maternal age, marital status, educational level, religion, employment status; husband’s educational level and employment status.Reproductive and obstetric: parity, breastfeeding duration after previous birth, pattern of menstrual cycles, use of modern contraceptives prior to conception, pregnancy intention, sex preference of previous child, decision making power regarding family planning.

Outcomevariables

Primary exposure variable: Inter pregnancy interval, defined as the time in months between the date of the previous live birth and the date of conception of the index pregnancy, calculated from reported last menstrual period or early ultrasound dating. Short IPI was defined as less than 24 months; optimal IPI as 24 - 59 months; and long IPI as 60 months or more.Maternal outcomes: anemia in pregnancy, third trimester bleeding, postpartum hemorrhage (PPH).Perinatal outcomes: preterm birth, birth asphyxia, stillbirth and other adverse neonatal outcomes.Knowledge outcome: level of maternal knowledge regarding optimal birth spacing and recommended IPI.

Datacollectionprocedures

After obtaining ethical and administrative approvals, trained research staff approached eligible women in the labour wards of each hospital. Study objectives and procedures were explained using a participant information sheet, and written informed consent (or documented verbal consent when literacy was limited) was obtained before enrolment.

Data was collected using an interviewer administered structured questionnaire complemented by review of patient files and admission registers. The questionnaire was developed based on the literature and pre tested on 10% of the target sample; identified issues were addressed before final deployment. It was available in English and French to facilitate comprehension.

Thequestionnairecaptured:

Socio demographic characteristics of the woman and her partner.Reproductive history and current pregnancy characteristics, including parity, breastfeeding practices after the previous birth, menstrual cycle regularity, contraceptive use and decision making on family planning.Maternal and perinatal outcomes for the index pregnancy, obtained from clinical records (e.g. hemoglobin levels, diagnosis of PPH, gestational age at birth, Apgar scores, stillbirth).Knowledge and attitudes regarding optimal birth spacing and inter pregnancy intervals using a series of Likert scale questions.

Each participant was followed through delivery and immediate postpartum to ensure complete outcome data for mother and neonate.

Knowledgeassessment

Knowledge of optimal birth spacing was evaluated using a five-point Likert scale for statements regarding recommended minimal and maximal IPIs, benefits of spacing, and definitions of short and long intervals. Responses ranged from “strongly disagree” (1 point) to “strongly agree” (5 points). For each statement, scores of 1 - 2 indicated poor responses, 3 average, and 4 - 5 good responses. An overall knowledge score was computed by averaging responses across items; scores ≥ 3 was classified as sufficient knowledge and scores < 3 as insufficient knowledge.

Knowledge Instrument and Scoring Structure

The questionnaire assessed maternal knowledge of optimal birth spacing and Inter-Pregnancy Intervals (IPI) through a dedicated section consisting of six items. Each item was evaluated using a five-point Likert scale.

Items and Content: The six items covered the minimum (2 years) and maximum (5 years) recommended intervals, the benefits of spacing (prevention of nutrient depletion), risks to the neonate (preterm birth), maternal risks (anemia), and the role of family planning.Scoring Range: Each item was scored from 1 (“Strongly Disagree”) to 5 (“Strongly Agree”). This resulted in an overall mean score range of 1 to 5 per participant.Categorization: Responses for individual items were classified as “poor” (1 - 2 points), “average” (3 points), or “good” (4 - 5 points).

Rationale for the “ Sufficient Knowledge ” Threshold

The threshold of a mean score ≥ 3 was established to identify women who, on average, at least “Agreed” with the correct health-seeking behaviors and biological rationales presented in the instrument. A score of 3 represents the “Average” or neutral point on the scale. By setting the cutoff at ≥3, the study classified “Sufficient Knowledge” as the ability to correctly identify or agree with the fundamental principles of birth spacing, rather than possessing only “poor” or incorrect perceptions (scores < 3).

Piloting and Reliability

To ensure the instrument’s robustness, the questionnaire underwent a formal pilot test prior to final deployment. Pilot Sample: The test was conducted on 10% of the target sample size. Refinement: Results from the pilot were used to identify and address issues with question clarity and comprehension, ensuring the tool was effective in both English and French for the study population.

Datamanagementandstatisticalanalysis

Data was double entered into Microsoft Excel and exported to SPSS version 25 for analysis. Categorical variables were summarized using frequencies and percentages; continuous variables such as age and parity were described using means and standard deviations.

Multivariable models included socio-demographic factors (age, education) and reproductive history (parity, contraceptive use) to control for confounding.

Bivariate analysis was performed to examine associations between potential determinants and short IPI as the dependent variable, using odds ratios (OR) with 95% confidence intervals (CI). Variables with p value < 0.05 at bivariate level were entered into a multivariable logistic regression model to control for confounding, and adjusted odds ratios (AOR) with 95% CI were reported. Similar bivariate and multivariable models were used to assess associations between short IPI and maternal and perinatal outcomes. Statistical significance was set at a two tailed p value < 0.05.

Ethicalconsiderations

Ethical clearance was obtained from the Institutional Review Board of the Faculty of Medicine and Pharmaceutical Sciences, University of Douala (ref. 3217IEC-UD/06/2022/T). Administrative authorizations were granted by the Faculty of Medicine and Pharmaceutical Sciences, Douala Laquintinie Hospital (ref. 01067/AR/MINSANTE/DHL) and Nylon District Hospital. Participation was entirely voluntary; informed consent was obtained from all participants, confidentiality was protected through use of unique identifiers and password protected databases, and no identifying information appears in this manuscript.

This study has several strengths. First, it uses primary data from two large urban public hospitals, providing robust insights into short IPI among women delivering in high volume facilities in Douala. Second, we assessed a comprehensive set of socio demographic and reproductive determinants and adjusted for confounding using multivariable logistic regression, enhancing the internal validity of associations. Third, we directly linked IPI to objectively measured maternal and perinatal outcomes (anemia, PPH, preterm birth) extracted from clinical records, rather than relying solely on self report. Finally, we integrated an assessment of knowledge of optimal birth spacing, enabling us to relate observed behaviors to underlying awareness and attitudes.

Short interpregnancy intervals are common among women delivering at Douala Laquintinie and Nylon District Hospitals, affecting approximately 43% of the study population. Young maternal age, low educational attainment, high parity, irregular menstrual cycles, short breastfeeding duration and non-use of modern contraception were key determinants of short IPI. Short intervals were independently associated with increased risks of maternal anemia, postpartum hemorrhage and preterm birth, corroborating the maternal depletion and folate depletion hypotheses and aligning with evidence from other African and global studies. While overall knowledge of optimal birth spacing was moderate, specific gaps—particularly regarding the recommended upper limit of 5 years—persisted. Integrating strengthened postpartum family planning counselling and focused educational interventions into routine maternity services in the two hospitals in Douala could substantially reduce short IPIs and improve maternal and perinatal outcomes.

Data collection was done by Dr FOFUNGTUM Massateh Ajui-Aseh while Dr NGALAME Alphonse drafted the manuscript. Critical revision of the manuscript was done by Prof. ESSOME Henri. Florence MENDOUA, Merlin BOTEN, Reine KOUNDO MOTAH, Moustapha BILKISSOU, Fulbert MANGALA, Ingrid OFAKEM, Lionel Oscar ESSOME TOCKY, Grace TOCKI TOUTOU and Estelle WAFO all read and corrected the manuscript. Overall supervision, coordination of writing and editing was ensured by Prof. EGBE Obinchemti Thomas. All authors read and approved of the final manuscript.