Undernutrition during pregnancy increases the risk of giving birth to a small vulnerable newborn. Small-quantity lipid-based nutrient supplements (SQ-LNSs) contain both macro- and micronutrients and can help prevent multiple nutritional deficiencies. We examined the effects of SQ-LNSs provided during pregnancy compared with iron and folic acid or standard of care (IFA/SOC), or multiple micronutrient supplements (MMS) and identified characteristics that modified the estimates of effects of SQ-LNSs on birth outcomes. SQ-LNSs had positive impacts on multiple outcomes compared to IFA/SOC, but further research directly comparing SQ-LNSs and MMSs is needed. Targeting SQ-LNSs to vulnerable subgroups may be worth considering.