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60 3.1 Preconception and Fertility
activity programme, the outcome for most women Eating disorders
was natural ovulation, conception and successful
pregnancy. Both anorexia nervosa and bulimia nervosa, which
are estimated to affect 1–2 per cent of young women
Excessive body fat especially central (Hoek 2006), are related to amenorrhoea,
obesity anovulation and infertility.
Central body obesity, indicated by a waist
circumference >90 cm (35 inches) is a risk factor Extreme levels of exercise
for infertility as it takes women with high
central obesity longer to become pregnant than High levels of exercise together with a low calorie
women with low central obesity (Zaadstra et al. intake in young women (calorie intake <30 per cent
1993). of requirements) can result in a condition known as
the ‘female athlete triad’ with three symptoms:
Underweight disordered eating, amenorrhoea and osteoporosis
Conception can occur in women well below (Loucks et al. 2006). The latter is as a result of low
average or ideal weight. However, women who have oestrogen production.
a low BMI (BMI <20) are less likely to conceive
(Zaadstra et al. 1993). Caffeine
Low per cent body fat High intakes of caffeine may extend the time it
A study in the 1990s in the United States showed takes to become pregnant. Researchers have
that an improved nutritional status in adolescent found that women who consumed more than
girls was associated with an increasingly early date four cups of coffee per day – about 500 mg
of menarche signalling the onset of fertility. The caffeine – were half as likely to conceive as
mean body weight at which menarche occurred in women who had less than two cups of coffee per
US girls was 48 kg with a mean height of 1.59 m at day (Committee on Toxicity 2008).
12.9 years. Of the mean body weight at the
completion of growth (16–18 years) 16 kg was fat, Poor iron stores
representing an energy reserve for reproduction of
602 MJ (144 000 kcal). Such an energy reserve Iron status prior to pregnancy is related to
would provide the theoretical energy requirements fertility. Results from a large prospective study of
of both pregnancy and three months of lactation. nurses (Chavarro et al. 2006) indicated that
Frisch’s observation was that body fat proportion anovulatory infertility may be related to poor iron
of less than 22 per cent of body weight was status.
associated with the absence of ovulation and that
healthy fertile women who were ovulating on a Alcohol
monthly basis had an average body fat proportion
of 28 per cent. A follow-up study of couples planning their first
pregnancy found an association between women’s
Weight loss and undernutrition alcohol intake and decreased fertility even among
women who had five or fewer drinks a week. This
In normal weight women, weight loss of 10–15 per would indicate that fertility is reduced in a high
cent causes hormonal disruption, resulting in proportion of women due to their alcohol intake
amenorrhoea and anovulation. About 30 per cent (Jensen et al. 1998). Women experiencing
of impaired fertility cases are related to weight loss. difficulties in conceiving should be advised of the
Weight gain is the recommended treatment for possible advantages of avoiding alcohol completely
amenorrhoea related to low body weight. (Jensen et al. 1998). The Department of Health
now advises avoiding alcohol altogether but if
women choose to drink alcohol it should be
