RESUMO
Natural sex selection methods have been applied for several decades, but their use and effectiveness are still a matter of debate. Therefore, this study assessed the efficacy of a maternal diet low in sodium and high in calcium, in combination with timing of intercourse well before ovulation as a method to improve the chances of conceiving a girl. A total of 172 couples wanting a girl participated in the study. For the 150 couples that actually started, compliance with diet was assessed through mineral analyses of blood and timing of intercourse relative to ovulation was determined by ovulation tests. Based on mineral blood values and timing of intercourse of 28 participants, a prediction rule for conceiving a girl was constructed and was tested prospectively for validity on a subsequent group of 50 women. In this group, 21 women satisfied the criteria of the prediction rule and 16 gave birth to a daughter. It is concluded that the combination of maternal diet with timing of intercourse is capable of increasing the probability of conceiving a girl (P=0.005). The observed percentage of female babies for all 32 women satisfying the prediction rule was 81% (95% confidence interval 68-95%).
