[Lactation and amenorrhea in women from the rural and urban areas of Yucatan]. / Lactancia y amenorrea en mujeres de las áreas rural y urbana de Yucatán.

ABSTRACT

PIP: 100 women in Yucatan, Mexico, participated in a longitudinal and prospective study of the influence of lactation patterns and rural or urban residence on the duration of amenorrhea and the frequency of ovulation before the first postpartum menstrual period. 50 women from the city of Merida and 50 from nearby villages were followed until their first postpartum menstruation. The women were of lower socioeconomic status and aged 20-31 years. All had breast fed at least two older children and none used contraception before the first postpartum menstruation. 25 women in each residence group practiced exclusive breast feeding in the first months and 25 mixed bottle and breast feeding. The women kept records of the number of nursing episodes or bottles given, and collected 24-hour urine samples weekly beginning in the fourth postpartum month for urinary pregnanediol determination. Monthly blood samples were obtained before and after nursing to measure prolactin levels. Ten of the 100 women withdrew before completion of the study. The women in all four subgroups were very similar in age, education, and family size. The average duration of amenorrhea was 10.58 months for the 49 rural women and 8.02 months for the 44 urban women, but the difference was not statistically significant. The 11.02 month duration of amenorrhea of the exclusively breast feeding mothers was significantly longer than the 7.34 months of the partially breast feeding group. At six months postpartum, nine exclusively breast feeding and 22 partially breast feeding mothers had resumed menstruation. 75 of the women (88.3%) resumed menstruation within one year. 13 women (14.4%) ovulated before the first menstruation, with an average duration of amenorrhea of 9.8 months. None of the women became pregnant before the first menstruation. Prolactin levels were significantly lower in the women who ovulated before the first menstruation.