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

Abstract

Background: The hormonal 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 the modulation of the endocrine system by cortisol and prolactin production during pregnancy.

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: Visit 1 (V1; 16-20 weeks of amenorrhea), Visit 2 (V2; 28 ±1 weeks of pregnancy), Visit 3 (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 during labour 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 titres and prolactin levels during the pregnancy and the post-partum.

Results: Results showed that cortisol and prolactin levels in the peripheral blood were globally 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 in the cord blood, and conversely for prolactin. Cortisol and prolactin levels decreased after delivery, though 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).

Conclusion: These results showed that the up-regulation effects of cortisol and prolactin are related to gestational age. A The downward regulation effect that both hormones have on each other during the pregnancy when each increase to 1 unit (1.0 ng/ml) was also reported.

Fig 1. Dynamics of cortisol levels measured in pregnant women during pregnancy determined at different ANC visits.

Legend: NS: not significant; V: visit. Code: *: <0.05; **: <0.01; ***: <0.001; ****: <0.0001. In each case, 30μl of plasma was used to determine for cortisol level in blood (ng/ml). Cortisol levels were compared between multigravidae and primigravidae at each scheduled visits and presented as box and whisker plots illustration: top, bottom and middle of box, representing 25^th, 75^th and 50^th percentiles, respectively. In both group, cortisol concentration increased in a sawtooth pattern during pregnancy with peaks at V2(28^th±1 week) and V4 32^th ±1 week), before decreasing at V5 which is part of post-partum.

Fig 2. Dynamic of prolactin in pregnant women during pregnancy.

Legend: NS: not significant; V: visit. Code: *: <0.05; **: <0.01; ***: <0.001; ****: <0.0001. 30μl of plasma was used to determine the concentration of prolactin in blood (ng/ml). Prolactin levels were compared between multigravidae and primigravidae at each scheduled visits as described in “Method” section and presented as box and whisker plots illustration: top, bottom and middle of box, representing 25^th, 75^th and 50^th percentiles, respectively. In multigravidae, the prolactin concentration increase from V1 (enrolment) to V4 (delivery) before decreasing at V5. For primigravidae, this concentration increase from V1 to V3 before decreasing at V4 and V5.