Natural selection for bipedal locomotion and encephalization creates an obstetric dilemma. Consequently, a trade-off occurs between human brain size, locomotory efficiency, and the increased risk of maternal and infant mortality from obstructed labour. The Maasai of Northern Tanzania, attempt to ease the obstetric dilemma by manipulating fetal growth. However, due to the tendency for growth restricted newborns to exhibit brain sparing, these maternal practices would have to achieve corresponding head and body size reductions. To determine the efficacy of this cultural adaptation to the obstetric dilemma, we interviewed traditional birth attendants and mothers about their maternal practices. Maternal diet was measured, and infant anthropometric data were collected on 141 maternal-infant pairs. Participants reported a 50% reduction in dietary intake. Of the 141 infant participants, 36 (25%) were growth restricted. The brain sparing tendency was observed among the growth restricted sample, suggesting that maternal dietary restriction does not overcome the obstetric dilemma.