Methods and findings
In a randomized controlled trial (RCT), short message service (SMS)-based mobile phone surveys were conducted to assess the causal effect of a food security intervention (improved on-farm storage of maize) on perceived stress and coping in pregnant women from smallholder households. Pregnant women were identified through these monthly surveys by asking whether someone in their household was currently pregnant. The significant results revealed that pregnant women from treatment households experienced more perceived stress but better perceived coping abilities compared to pregnant women from control households. Uncertainty due to lack of experience, this might have contributed to the higher perceived stress, as the women could not easily judge the benefits and risks of the new storage technology. However, the technology itself is a tangible resource which might have empowered the pregnant women to counteract the effects of PHL and thus food insecurity.