Background: Birth weight is the most important factor determining the survival, growth and development of a newborn. Parity and maternal age have been shown to increase the risk of adverse neonatal outcomes, such as intra-uterine growth restriction (IUGR), low birth weight (LBW) and mortality.

Objective of the study: The study was aimed at investigating the effects of maternal age and parity on the birth weight of newborns from singleton pregnancies and term deliveries.

Materials and Methods: An institutional-based, retrospective, cross-sectional study design was employed at Tikur Anbessa Specialized Hospital (TASH), Addis Ababa, Ethiopia from April to July 2018. In total, 4,590 mothers with term delivery and singleton pregnancy from June 2015 to May 2017 were included in the study. Data on gestational age (GA), parity, history of ANC follow-up, source of referral and birth weight of the child was included. The collected data were analyzed using SPSS version 23 statistical package, and multiple logistic regression was carried out to determine the effect of maternal age and parity with respect to LBW.

Results: Grand multiparous women (parity ≥5) have an adjusted odds ratio (AOR) of 3.89 with 95% confidence interval (CI = 2.19, 6.93) compared to multiparous women (p=2-4). Nulliparous women (p=0) have an AOR of 0.23 (95%CI = 0.19, 0.38) compared to multiparous women. Primiparous women (p=1) have an AOR of 0.22 (95% CI = 0.16, 0.30) compared to multiparous women. Women aged 40 and above have an AOR of 1.96 (95% CI = 1.22, 3.20) compared to women aged 30-34. The mean birth weight (MBW) of newborns was 3,075.41±569.58 grams (mean±SD).

Conclusions: In this study, the risk of LBW was higher in grand multiparous women compared to multiparous women. Primiparous and nulliparous women have less risk of having an LBW baby compared to multiparous women. A maternal age of 40 and above were associated with a higher risk of delivering an LBW newborns compared to a maternal age of 30-34. Therefore, special attention should be given to deliveries at an advanced age and multiparous cases to reduce the incidence of LBW.