FERTILITY AND FATNESS

                                   

     It has been well established that fertility and fatness are closely related with subfertility related problems occurring in women below and above the desirable range of body weight. Where diet is restricted or accompanied by high levels of training such as in balet dancers and athletes, or both, the menarch can be delayed, and secondary amenorrhoea and irregular cycles are common after the menarch. The average post pubertal woman has a body fat content of approximately 28%: a minimum of 22% is required for the maintenance of ovulation. Conditions such as thyrotoxicosis, malabsorption syndromes, eating disorders such as anorexia nervosa and bulimia nervosa and psychological stress can result in secondary amenorrhoea. Weight gain as a result of  increasing energy intake of reducing training regimes, or both, is usually sufficient to re-establish ovulation in underweight women.

Fat distribution is also important as increased waist-hip ratio, where fat distribution is predominantly around the abdomen as opposed to the hips and thighs, is associated with reduced chances of conception are possible when a programme of weight loss and exercise is adhered to.

     A woman’s nutritional status before pregnancy and during the first weeks before realizing that she is pregnant may be more important than the diet she eats once her pregnancy is confirmed. By this time much of the cell organization, differentiation and organogenesis will have taken place. Suboptimal conditions at this time can result in fetal damage and stunted growth. An optimum BMI for maximum fertility and for producing a healthy baby of normal birth weight appears to be around 23. Low maternal weight before conception is associated with and increased risk in low birth weight babies and symmetrical growth restriction and for women with a BMI below 19.1 noted a fivefold increase in low birth weights.

     The aim of fertility care is to help such women achieve an appropriate BMI prior to conception to enhance pregnancy outcome. Overweight women should be encouraged to lose weight before conception. However, some caution is required as consuming an energy- deficient diet immediately prior to conception may result in nutritional deficiencies that could disadvantage the fetus.

     Dietary changes and weight loss is important for fertility maintenance and should occur at least 3-4 months before attempting conception.