Time-sensitive changes in the maternal brain and their influence on mother-child attachment

Abstract

Pregnancy and the postpartum period are characterized by an increased neuroplasticity in the maternal brain. To explore the dynamics of postpartum changes in gray matter volume (GMV), magnetic resonance imaging was performed on 20 healthy postpartum women immediately after childbirth and at 3-week intervals for 12 postpartum weeks. The control group comprised 20 age-matched nulliparous women. The first 6 postpartum weeks (constituting the subacute postpartum period) are associated with decreasing progesterone levels and a massive restructuring in GMV, affecting the amygdala/hippocampus, the prefrontal/subgenual cortex, and the insula, which approach their sizes in nulliparous women only around weeks 3-6 postpartum. Based on the amygdala volume shortly after delivery, the maternal brain can be reliably distinguished from the nulliparous brain. Even 12 weeks after childbirth, the GMV in the dorsomedial prefrontal cortex, and the cortical thickness of the subgenual and lateral prefrontal cortices do not reach the pre-pregnancy levels. During this period, a volume decrease is seen in the cerebellum, the thalamus, and the dorsal striatum. A less hostile behavior toward the child at 6-12 weeks postpartum is predicted by the GMV change in the amygdala, the temporal pole, the olfactory gyrus, the anterior cingulate, the thalamus and the cerebellum in the same period. In summary, the restructuring of the maternal brain follows time-dependent trajectories. The fact that the volume changes persist at 12 weeks postpartum indicates that the maternal brain does not fully revert to pre-pregnancy physiology. Postpartum neuroplasticity suggests that these changes may be particularly significant in the regions important for parenting.

Fig. 1. Boxplots of natural log-transformed (ln) mean plasma concentration of estradiol and progesterone with 25th and 75th percentile as well as minimum and maximum.

The lines represent the plasma concentration of the hormones on the respective sampling day for each individual.

Fig. 2

Smaller gray matter volume in postpartum women compared to nulliparous participants throughout the postpartum period.

Fig. 3. Postpartum longitudinal changes in gray matter volume.

A Postpartum gray matter volume increase at 3 weeks postpartum compared to childbirth, 6 weeks compared to 3 weeks and 9 weeks compared to 6 weeks. *The comparison 9 weeks vs. 6 weeks postpartum was performed with cluster-forming threshold to p < 0.005, using a p < 0.05 cluster-level FWE-correction. B Postpartum gray matter volume decrease from childbirth to 6 weeks postpartum and from 3 weeks to 9 and 12 weeks postpartum.

Fig. 4. Multivariate regression analyses.

A Classification plot comparing nulliparous and postpartum women. Positive function values for postpartum women indicates true positives. Negative function values for nulliparous participants indicates true negatives. B Receiver operating characteristic (ROC) curve showing classification performance. C Gray matter volume change from 9 weeks to 12 weeks postpartum predicts the total score of the Maternal Postnatal Attachment scale, the score of the subscale Absence of Hostility, and, by trend, the score of the subscale Quality of Attachment.

Fig. 5. Changes in cortical thickness.

A Greater cortical thickness in nulliparous women compared to postpartum women at all study time points (pp). B Increase of cortical thickness in the postpartum period.