Immunomodulatory effects of gestational age on blood cortisol and prolactin levels during pregnancy in malaria endemic area

Abstract Background: The immunological shift occurring in pregnant women is crucial for the outcome of pregnancy. We conducted a study in pregnant women living in a malaria endemic area to determine the potential effect of gestational age on modulating the immune system by cortisol and prolactin production. Methods: Primigravidae and multigravidae with a gestational age between 16-20 weeks were included in the study and followed up to delivery and 6-7 weeks thereafter. Venous blood was collected at scheduled visit: Visit1 (V1; 16-20 weeks of amenorrhea), Visit2 (V2; 28 ±1 weeks of pregnancy), Visit3 (V3; 32 ±1 weeks of pregnancy), Visit4 (V4; delivery) and Visit5 (V5; 6-7 weeks after delivery). In addition, a cord blood sample was also collected at delivery. Nulliparous and primiparous/multiparous non-pregnant women were enrolled in the control group. Cortisol and prolactin plasma concentrations were measured using ichroma II and i-chamber apparatus. Light microscopy was used to detect Plasmodium falciparum infections. A linear mixed-effects regression (LMER) model was used to assess the association between the variation of cortisol titters and prolactin levels during the pregnancy and the post-partum. Results: Results showed that cortisol and prolactin levels in the peripheral blood were up-regulated during pregnancy. Concentrations of cortisol during follow-up was significantly higher in primigravidae than in multigravidae during the whole pregnancy (p<0.024). Moreover, the level of prolactin which was higher before delivery in primigravidae reversed at delivery and postpartum visit, but the difference was not statistically significant during the follow-up (V1 to V5) (p=0.60). The cortisol level in peripheral blood at delivery was higher than that of the cord blood, and conversely for prolactin. Cortisol and prolactin levels decreased after delivery, thought the level of prolactin was still higher than that at enrolment. An increase of one unit of prolactin was associated with the decrease of the average concentration of cortisol by 0.04 ng/ml (p=0.009). However, when cortisol increases with one unit, the average concentration of prolactin decreases by 1.16 ng/ml (p=0.013). Asymptomatic malaria infection in general leads to a non-statistically significant increase or decrease of the average concentration of prolactin (32.39 ng/ml; 95% CI: -45.82 to 110.59; p=0.414) and cortisol (-3.15 ng/ml; 95% CI: -17 .94 to 11.65; p=0.675), respectively. Conclusion: These results showed that the potential effects of cortisol and prolactin are related to gestational age. This could affect the susceptibility of pregnant women to infectious diseases such as malaria in endemic areas.