The influence of toxoplasmosis on pregnancy length at pregnancy week 16 estimated based on the first ultrasonography was evaluated by the GLM in the set of 915 mothers. The result showed that 185 Toxoplasma-infected subjects had a shorter pregnancy (111.56 days) than 730 Toxoplasma-free subjects (112.59 days) (F1,911 = 6.1, P = 0.0137). The continuous predictors in the model were also significant: maternal age (F1,911 = 4.0, P = 0.0456), and presumptive pregnancy length estimated from the date of the last menstruation (F1,911 = 484.0, P < 0.0001). The same model was used for evaluating the effects of toxoplasmosis separately in women with male and female offspring. In both cases the influence of latent toxoplasmosis on pregnancy length was significant in one-tailed tests (male newborns: n = 507, F1,503 = 3.5, P1 = 0.0313, female newborns: n = 396, F1,392 = 2.9, P1 = 0.0459). The separate tests for primiparous and multiparous women showed that the effect of toxoplasmosis was significant for multiparous women (n = 362, F1,358 = 5.8, P = 0.0164), while for primiparous women this effect was not significant (n = 553, F1,549 = 1.3, P = 0.2546) (Figure ).
Figure 1 Differences in pregnancy length estimated based on ultrasonography at pregnancy week 16 (estimated from the date of the last menstruation) between Toxoplasma-infected and Toxoplasma-free women. Left graph, primparas (P = 0.2546), right graph, multiparas (more ...)
Toxoplasmosis had no effect on fetal bioparameters measured by ultrasonography at pregnancy weeks 20 and 30 in both the whole study set (Table ) and the subset of multiparous women (not shown). Similarly, toxoplasmosis had no effect on newborn's birth length and weight both in the whole study set: birth length (n = 784, F1,780 = 1.6, P = 0.2071, averages: 50.47 cm in Toxoplasma-infected and 50.66 cm in Toxoplasma-free women), birth weight (n = 962, F1,958 = 0.00, P = 0.9872, averages: 3497.61 g in Toxoplasma-infected and 3493.44 g in Toxoplasma-free women) and in the subset of multiparous women: birth length (n = 324, F1,320 = 2.9, P = 0.0873, averages: 50.30 cm in Toxoplasma-infected and 50.77 cm in Toxoplasma-free women), birth weight (n = 398, F1,394 = 0.23, P = 0.6284, averages: 3499.61 g in Toxoplasma-infected and 3535.18 g in Toxoplasma-free women).
Fetal ultrasonography data in Toxoplasma-infected and Toxoplasma-free women at pregnancy weeks 20 and 30
Toxoplasma-infected women had longer pregnancy than Toxoplasma-free women (281.03 vs. 279.82 days, based on ultrasonography) (283.02 vs. 281.65 days, based on the date of the last menstruation) (Figures and ). The effects of toxoplasmosis and maternal age on pregnancy length were significant (based on ultrasonography: n = 884, F1,881 = 5.0, P = 0.0256, maternal age: F1,881 = 4.3, P = 0.0378), (based on the date of the last menstruation: n = 871, F1,868 = 5.9, P = 0.0151, maternal age: F1,868 = 18.0, P = 0.0001). To estimate influence of available confounding variables and interactions, we also analysed two models with independent variables TOXO, newborn's SEX and PARITY (0 – primipara, 1 – multipara), and the dependent variable pregnancy length estimated either based on ultrasonography or from the date of the last menstruation. The effect of TOXO on pregnancy length estimated both based on ustrasonography and from the date of last menstruation was significant (pregnancy lengthUSG: n = 882, F1,873 = 4.9, P = 0.0264, maternal age F1,873 = 3.9, P = 0.0491, newborn's SEX F1,873 = 0.9, P = 0.3303, PARITY F1,873 = 1.5, P = 0.199; pregnancy lengthLM: n = 869, F1,860 = 6.1, P = 0.0138, mother's age F1,860 = 16.6, P = 0.0001, newborn's SEX F1,860 = 0.2, P = 0.674, PARITY F1,860 = 0.6, P = 0.663). On the other hand, no effect of interaction, including TOXO-PARITY and TOXO-newborn's SEX, was significant in any model.
Differences in pregnancy length estimated from the date of the last menstruation between Toxoplasma-infected and Toxoplasma-free women (P = 0.0151).
Differences in pregnancy length estimated based on ultrasonography between Toxoplasma-infected and Toxoplasma-free women (P = 0.0256).