Underweight pregnant mothers in Northern Ghana are at risk of adverse birth outcomes due to inadequate nutrition. A mixed-methods approach combining anthropometric measurements with qualitative interviews was employed to assess maternal feeding practices and neonatal birth weights in a sample of 150 underweight pregnant women in Northern Ghana. Maternal undernutrition was significantly associated with lower birth weight, with an average newborn weight of 2.7 kg compared to the national average of 3.3 kg (95% CI: -0.6 to -0.1). Nutritional interventions are essential for improving feeding practices and reducing underweight births in Northern Ghana. Healthcare providers should prioritise nutritional education and support for underweight pregnant mothers, with a focus on increasing breast milk intake and dietary diversification. Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.