Study objective -To establish the degree of validity of data on time to pregnancy, derived retrospectively using a short questionnaire. Design -Information from the questionnaire was compared with data that had been collected concurrently from the same individuals. Setting and participants -Questionnaires were mailed to 1647 women who continue to be followed up by the Oxford Family Planning Association contraceptive study, and a further 424 were approached for personal interview. Response rates were 91% and 79% respectively. Main results -Matching was successful in 91% of pregnancies. Median recall time was 14 years (interquartile range, 11-16 years). At the group level, remarkably good agreement was found between the two sources of information, presented as cumulative percentage distributions oflive births. The findings were at least as good with longer recall (>14 years) as with shorter recall. Digit performance was present to a limited degree. At the individual level, some misclassification was evident, which has implications for statistical power. For detection of clinical infertility (no conception within 12 months), the sensitivity was in the range 67%/o-91%, and the specificity was 920/o-96%. Vari

1. Female weanling rats were fed on a purified diet containing either no vitamin A, apart from traces present in casein (deficient groups), or the same diet containing 1.55 mg retinol as retinyl acetate/kg (control groups). In one experiment the deficient groups were given 1 μg retinol/d after 10 weeks, to permit successful reproduction under conditions of marginal vitamin A status. A proportion were mated at 11 weeks after weaning, and fetal development was permitted for 7 d or for 20 d before killing.2. Carotene dioxygenase (EC 1. 13.11.21) activity was measured in a supernatant fraction from intestinal mucosal scrapings. For each group, activity was 20–30% greater in the vitamin-A-deficient animals than in the controls, and the difference reached statistical significance for the virgin and 7 d pregnant animals in the first experiment (severe deficiency) and for the 20 d pregnant animals in the second experiment (less-severe deficiency).3. It is suggested that low tissue vitamin A levels may feedback to increase carotene dioxygenase activity, by mechanisms at present unknown, presumably to ensure a more efficient use of precursor dietary carotenoids.

Preliminary studies on the bacterial flora of faeces taken from foals, from birth to twelve weeks. Effect of the oral administration of a commercial colostrum replacer. The faecal microflora of 18 normal, two month-old foals was composed of aerobes and facultative anaerobes, mainly Enterococci (107 CFIJ/g of faeces) and Lactobacilli (103 CFU/g) and strict anaerobes, cellulolytic bacteria (105 CFU/g) and Clostndia (104 CFU/g). At this early age ditferent bacterial stralns colonized the gut according to a specific sequence which could be modified by the oral adminlstration of a commercial colostrum replacer. The faecal microflora of 5 foals fed this colostrum at birth and once every t\i/o weeks during the first three months appeared to contain less cellulol!,tic bacteria and no Lactobacilli. The small number of foals treated limited our interpretation.

Plasma carotenoid levels exhibited a major seasonal variation in pregnant and lactating women in Keneba, a rural Gambian village. This is probably due mainly to the seasonally related contribution of mangoes, which are a major dietary component during May and June, but are essentially unavailable for the remainder of the year. Plasma retinol levels, on the other hand, exhibited much less seasonal variation, although a trend towards higher levels in May and June was just discernible. Plasma retinol levels were significantly lower than those observed in a group of pregnant and lactating women living in the UK.

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