Placental Weight and Neonatal Anthropometric Outcomes Among Term Deliveries in Nigeria: Does Maternal HIV Status Matter?

1. Introduction

The placenta is a highly specialised organ that plays a central role in foetal growth, development, and survival throughout pregnancy. It functions as the interface between maternal and foetal circulations, facilitating nutrient transport, gas exchange, waste elimination, endocrine signalling, and immunological regulation [1]. As this interface, it is also a biologically plausible site through which maternal human immunodeficiency virus (HIV) infection, HIV-associated immune activation and coinfections may influence foetal development [2]. Maternal HIV infection remains an important determinant of pregnancy health in sub-Saharan Africa. Mothers living with HIV may still experience increased risks of preterm birth, low birth weight, and small-for-gestational-age birth; estimates vary across settings and treatment eras [3]. The mechanisms are likely multifactorial and may involve maternal disease severity, persistent inflammation, coinfections, nutritional and socioeconomic factors [2].

Placental weight is regarded as one of the most accessible and reproducible macroscopic placental parameters in obstetric practice. Because placental growth reflects both maternal and foetal influences, placental morphology and weight may provide a practical indication of intrauterine conditions and foetal wellbeing [4]. Previous studies have demonstrated that placental weight correlates with foetal growth and neonatal outcomes, particularly birth weight and body length [4-7]. A disproportionately small placenta may indicate impaired placental perfusion, placental insufficiency, or inadequate nutrient transfer, whereas excessively large placentas have also been associated with adverse maternal and foetal conditions, including diabetes mellitus and foetal hydrops [8]. Neonatal birth weight and crown-heel length remain widely used indicators of neonatal health and intrauterine growth [9], while umbilical cord length may reflect foetal movement, placental vascular development, and pregnancy outcomes [10].

In HIV-affected pregnancies, reported placental findings include low placental weight, acute chorioamnionitis, and maternal vascular malperfusion, although these findings are not specific to HIV and can be modified by coinfection, comorbidity, and antiretroviral therapy exposure [2]. Nigerian evidence is limited and not uniform: a study in Uyo reported lower placental and birth weights and more inflammatory lesions among HIV-positive mothers [11], and a recent case-control analysis reported lower placental weight and shorter umbilical cords in HIV-positive pregnancies [12]. Conversely, a Kenyan prospective cohort found comparable risks of pregnancy loss, prematurity, and low birth weight among women with treated HIV and women without HIV [13].

The relationship between placental weight and neonatal birth weight has been extensively investigated in high-income settings; however, evidence from sub-Saharan Africa remains comparatively limited. This is particularly relevant because maternal nutritional status, infectious diseases, socioeconomic disparities, and access to antenatal care may substantially influence placental development and foetal growth in low- and middle-income countries [14]. Restricting analysis to term deliveries addresses a specific unresolved question: among pregnancies that reach term, does maternal HIV status remain associated with gross placental growth or neonatal anthropometry? Such data are pertinent in Nigeria, where placental examination offers a low-cost assessment in routine obstetric care.

This study therefore aimed to determine whether maternal HIV status was associated with placental weight, umbilical cord length, and neonatal anthropometric outcomes among term deliveries in southeastern Nigeria. It also assessed the associations between placental weight and neonatal birth weight and length.

2. Materials and Methods

This was a hospital-based cross-sectional analytical study conducted at the obstetrics unit of Nnamdi Azikiwe University Teaching Hospital located in Nnewi, southeastern Nigeria. Ethical approval for this study was obtained from the Research Ethics Committee of the Faculty of Basic Medical Sciences, Nnamdi Azikiwe University, with approval number NAU/CHS/NC/DBMS/1021. Written informed consent was obtained from participants where applicable. Confidentiality and anonymity of participant data were maintained throughout the study.

2.1. Study Population

The study was carried out among women who delivered term neonates at the study centre during the study period. The study population comprised mothers with term deliveries and their neonates.Women with term deliveries between 37 and 42 completed weeks of gestation, live-born neonates, and intact placentas available for examination were included in the study. The last menstrual period (LMP) was used to estimate the gestational age; for those unsure of dates, a record of early ultrasound dating was utilised. Preterm deliveries, grossly malformed neonates, severely damaged placentas unsuitable for measurement, and cases with incomplete clinical records were excluded from the study. A total of 273 term deliveries were included in the study using a consecutive sampling technique. Maternal demographic and clinical information were obtained from medical records and delivery registers. Maternal morbidities, if present, were documented, with particular attention to HIV infection. Following delivery, the placenta was examined immediately after expulsion. Blood clots were gently removed, and the umbilical cord was trimmed close to its insertion site. Placental weight was measured using a calibrated weighing scale.

2.2. Measurement and Data Analysis

Umbilical cord length was measured from the fetal insertion site to the placental insertion site using a non-elastic measuring tape and recorded in centimetres. Neonatal birth weight was measured using a calibrated neonatal weighing scale and recorded in kilograms. Neonatal crown–heel length was measured using a standard infantometer and recorded in centimetres. The dependent variables in this study were neonatal birth weight and neonatal length. The independent variables included placental weight, umbilical cord length, and maternal/fetal morbidities, including hypertension, HIV infection, diabetes mellitus, and Rhesus-negative status.

Data were entered into Microsoft Excel and analysed using Stata version 19.5 (StataCorp LLC, College Station, Texas, USA). Continuous variables were assessed for normality using graphical inspection and summary statistics. Normally distributed variables were presented as mean ± standard deviation, whereas categorical variables were summarized using frequencies and percentages. Pearson correlation analysis was used to assess relationships between placental weight, neonatal birth weight, neonatal length, and umbilical cord length. Correlation matrices and scatter plots were generated to visualize associations between variables. Simple linear regression analysis was performed to determine whether placental weight predicted neonatal anthropometric outcomes. Subsequently, multivariable linear regression models were constructed to assess whether placental weight independently predicted neonatal birth weight and neonatal length after adjustment for selected maternal and fetal factors, including maternal/fetal morbidity and umbilical cord length. Regression coefficients (β), 95% confidence intervals (CI), and p-values were reported. Statistical significance was set at p < 0.05.

3. Results

3.1. General Characteristics of the Study Population

A total of 273 term deliveries were included in the study (Table 1). Placental weight ranged from 0.20 to 1.10 kg with a mean value of 0.64 ± 0.16 kg. Umbilical cord length ranged from 30 to 125 cm with a mean value of 58.58 ± 11.93 cm. Neonatal birth weight ranged from 0.80 to 5.40 kg with a mean value of 3.16 ± 0.61 kg, whereas neonatal length ranged from 28 to 72 cm with a mean value of 51.25 ± 5.72 cm. Most deliveries had no documented maternal or foetal morbidity. Among documented comorbidities, HIV infection was the most frequent.

Pearson correlation analysis (Table 2) demonstrated a moderate positive correlation between placental weight and neonatal birth weight (r = 0.582, p < 0.001). Placental weight also showed a weak but statistically significant positive correlation with neonatal length (r = 0.230, p < 0.001). A positive association was also observed between placental weight and umbilical cord length (r = 0.180, p = 0.003). Neonatal birth weight and neonatal length demonstrated a moderate positive correlation with each other.

3.2. Correlational Analyses

Pearson correlation analysis (Table 2) demonstrated a moderate positive correlation between placental weight and neonatal birth weight (r = 0.582, p < 0.001). Placental weight also showed a weak but statistically significant positive correlation with neonatal length (r = 0.230, p < 0.001). A positive association was also observed between placental weight and umbilical cord length (r = 0.180, p = 0.003). Neonatal birth weight and neonatal length demonstrated a moderate positive correlation with each other.

Simple linear regression analysis demonstrated that placental weight significantly predicted neonatal birth weight. In the multivariable linear regression model (Table 3) adjusted for umbilical cord length and maternal/foetal morbidity, placental weight remained an independent predictor of neonatal birth weight (β = 2.22, 95% CI: 1.84–2.61, p < 0.001). Umbilical cord length and maternal/foetal morbidity did not independently predict neonatal birth weight in the adjusted model. Placental weight significantly predicted neonatal length in both unadjusted and adjusted analyses. After adjustment for cord length and maternal/foetal morbidity, placental weight remained independently associated with neonatal length (β = 7.21, 95% CI: 2.96–11.46, p = 0.001) (Table 3). Umbilical cord length also independently predicted neonatal length (β = 0.081, 95% CI: 0.025–0.137, p = 0.005). There were no significant differences in placental weight, neonatal birth weight, neonatal length, or umbilical cord length between mothers with and without HIV infection (all p > 0.05) (Table 4).

4. Discussion

The principal HIV-related finding of this study was that maternal HIV status was not associated with statistically significant differences in placental weight, umbilical cord length, neonatal birth weight, or neonatal length among term deliveries. At the same time, placental weight was significantly associated with neonatal birth weight and length and with umbilical cord length. These results suggest that, within this term delivery cohort, gross placental growth was a stronger correlate of neonatal size than maternal HIV status alone.

The absence of significant HIV-associated anthropometric differences is consistent with a prospective Kenyan cohort in which women with treated HIV and women without HIV had comparable risks of pregnancy loss, prematurity, and low birth weight [13]. It contrasts, however, with Nigerian studies from Uyo that reported lower placental and birth weights among HIV-positive mothers [11] and lower placental weight and shorter umbilical cords in HIV-positive pregnancies [12]. It also differs from pooled evidence suggesting that, despite antenatal antiretroviral therapy, HIV is associated with higher risks of preterm birth, low birth weight, and small-for-gestational-age birth [3]. The present finding should therefore be interpreted as evidence specific to the study population and measured outcomes, rather than as evidence that HIV has no placental or perinatal effect.

A number of features of the study may explain these differences. By design, the analysis excluded preterm deliveries, thereby removing one of the adverse outcomes most consistently associated with HIV and focusing on pregnancies that had already reached term. This restriction may have reduced the contrast between HIV-positive and HIV-negative groups. In addition, only 51 participants had HIV infection, which limited power to detect modest differences. Antiretroviral therapy exposure, regimen and timing, treatment adherence, viral load, CD4 cell count, and HIV disease stage were not available for analysis. Effective treatment and viral suppression could attenuate differences, whereas uncontrolled disease or particular treatment exposures could increase them; these possibilities could not be distinguished in the present dataset.

Placental weight is also a gross measure and may not capture microscopic or functional placental abnormalities. Among South African women with HIV, Ikumi, et al. [15] found similar gross placental measures by antiretroviral therapy initiation timing but a higher risk of maternal vascular malperfusion with preconception antiretroviral therapy. Nigerian histopathological work has likewise described acute chorioamnionitis, umbilical phlebitis, and villous vasculopathy in placentas from HIV-positive mothers [11]. Accordingly, the absence of a difference in placental weight in this study does not exclude HIV- or antiretroviral therapy-related changes in placental inflammation, vascular perfusion, exchange capacity, or efficiency.

The mean placental weight observed in this study was comparable to values previously reported in African and international populations. Placental weight varies across populations and may be influenced by maternal nutrition, ethnicity, environmental exposures, and socioeconomic conditions [16]. A major finding was the moderate positive correlation between placental weight and neonatal birth weight. This supports the concept that placental growth and foetal growth are closely interrelated. The placenta regulates the transfer of oxygen and nutrients to the foetus, and larger placentas generally possess greater exchange surface area and vascular capacity, potentially supporting greater foetal growth [1]. Similar positive relationships between placental weight and birth weight have been reported across diverse populations [16,17].

Placental weight also demonstrated a statistically significant positive association with neonatal length, although the magnitude was weaker than that observed for birth weight. This may indicate that placental weight more strongly reflects foetal soft-tissue accretion and overall mass than linear skeletal growth alone. The positive association between placental weight and umbilical cord length further suggests that placental and cord development may occur in parallel, potentially reflecting coordinated fetoplacental growth [10]. Because placental examination is inexpensive, rapid, and routinely feasible, placental weight may provide additional insight into neonatal growth status in low-resource settings; however, it should complement rather than substitute for clinical, virological, or histopathological assessment in HIV-affected pregnancies.

This study has several strengths, including direct measurement of placental and neonatal anthropometric parameters, inclusion of a clearly defined term-delivery cohort, and use of multivariable regression to evaluate independent predictors of neonatal outcomes. However, the cross-sectional design precludes causal inference. Detailed maternal variables such as body mass index, parity, nutritional status, gestational-age stratification, and socioeconomic indicators were not available. The HIV analysis was further limited by the modest number of HIV-positive participants and the absence of ART, viral-load, CD4-count, disease-stage, infant HIV-status, and placental histopathology data. Residual confounding and exposure misclassification are therefore possible.

Future studies should incorporate larger multicentre cohorts with deliberate recruitment of women living with HIV and detailed measurement of ART regimen and timing, adherence, viral suppression, CD4 count, coinfections, nutrition, and socioeconomic factors. Analyses stratified by foetal sex and gestational age could identify effects that are obscured in pooled term data [18]. The HIV-null finding should be interpreted within the restriction. Histopathological assessment standardised placental weight-for-gestational-age measures, and evaluation of placental efficiency indices would further clarify whether HIV or ART alters placental structure and function even when gross weight and neonatal anthropometry appear comparable.

Among term deliveries at the study centre, maternal HIV status was not significantly associated with placental weight, umbilical cord length, neonatal birth weight, or neonatal length. Placental weight nevertheless demonstrated significant positive associations with neonatal birth weight, neonatal length, and umbilical cord length and independently predicted neonatal anthropometric outcomes after adjustment for selected maternal and foetal factors. These findings support the potential utility of placental weight as a simple surrogate marker of foetal growth and intrauterine health.

5. Conclusion

Among term deliveries at the study centre, maternal HIV status was not significantly associated with placental weight, umbilical cord length, neonatal birth weight, or neonatal length. Placental weight nevertheless demonstrated significant positive associations with neonatal birth weight, neonatal length, and umbilical cord length and independently predicted neonatal anthropometric outcomes after adjustment for selected maternal and foetal factors. These findings support the potential utility of placental weight as a simple surrogate marker of foetal growth and intrauterine health.