Helminth infection, fecundity, and age of first pregnancy in women - PubMed (original) (raw)

Helminth infection, fecundity, and age of first pregnancy in women

Aaron D Blackwell et al. Science. 2015.

Abstract

Infection with intestinal helminths results in immunological changes that influence co-infections, and might influence fecundity by inducing immunological states affecting conception and pregnancy. We investigated associations between intestinal helminths and fertility in women, using 9 years of longitudinal data from 986 Bolivian forager-horticulturalists, experiencing natural fertility and 70% helminth prevalence. We found that different species of helminth are associated with contrasting effects on fecundity. Infection with roundworm (Ascaris lumbricoides) is associated with earlier first births and shortened interbirth intervals, whereas infection with hookworm is associated with delayed first pregnancy and extended interbirth intervals. Thus, helminths may have important effects on human fertility that reflect physiological and immunological consequences of infection.

Copyright © 2015, American Association for the Advancement of Science.

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Figures

Figure 1

Figure 1

Associations between infection and likelihood of becoming pregnant. (A–C) Kaplan-Meier curves from cox-proportional hazard models (Table 2), representing the time to first pregnancy (A), and time to subsequent pregnancies at age 25 (B) and age 40 (C). Hazard ratios for conception associated with infection across ages are shown in (D). Colors indicate uninfected (dashed brown), infected with hookworm (solid dark green), or infected with A. lumbricoides (solid mustard).

Figure 2

Figure 2

Reproductive careers predicted from Cox proportional hazard models, showing the expected distributions of reproductive values for hypothetical women with constant parasite status throughout life. Outcomes include: age at first birth (A), interbirth intervals (B), age at last birth (C), age specific fertility (births/woman/year) (D), median cumulative fertility over time (E), and total completed fertility at age 50 (F). Colors indicate uninfected (U; brown), infected with hookworm (H; dark green), infected with A. lumbricoides (A; mustard), or coinfected with hookworm and A. lumbricoides (C; light blue). Boxplot whiskers display the 5th and 95th percentiles, bodies the 25th, 50th, and 75th. Predictions are derived from the models in Figure 1.

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