The 4th trimester of pregnancy: postpartum and its hormones

The 4th trimester of pregnancy refers to the post-partum period, i.e. after childbirth. This period varies: from 3 to 6 months after birth.

This is a time of many changes for women, both physical and psychological.

Prolactin is an essential hormone that gradually increases during pregnancy, reaching a peak at the moment of birth. It plays a crucial role not only in lactation, but also in the mother-child bond. By promoting the production of breast milk, prolactin helps nourish the newborn and establish an intimate connection between mother and baby.

Beyond lactation, prolactin has other important functions. It promotes deep sleep and sleep on the part of the mother, which is vital for recovering from childbirth and coping with the demands of motherhood. Good sleep quality also helps to stabilize mood and prevent post-partum depression.

Prolactin secretion is stimulated by the simultaneous sucking of both nipples. So, when a mother expresses milk, double pumping is recommended to maximize prolactin, and therefore milk, production. This helps maintain adequate milk production and meet the infant's nutritional needs.

In terms of timing, prolactin secretion begins to increase around 10 to 30 minutes after the start of breastfeeding. This rapid response helps to ensure continuous and sufficient feeding for the baby. By supporting these processes, prolactin plays an indispensable role in the health and well-being of both mother and child in the post-partum period.

Progesterone, a crucial hormone during pregnancy, increases steadily until delivery. Progesterone is mainly produced by the placenta, and plays a vital role in maintaining pregnancy by preparing the uterus to receive and nourish the embryo. It also helps modulate the immune system to prevent rejection of the fetus by the mother's body.

At birth, with the detachment and expulsion of the placenta, progesterone levels drop rapidly. This sudden drop marks a significant hormonal change for the mother. The drop in progesterone is a trigger for the milk supply, facilitated by the increase in prolactin.

The decline in progesterone after childbirth also has implications for the mother's mood and well-being. The rapid hormonal drop can contribute to feelings of fatigue, sadness and even post-partum depression in some women. That's why it's essential to monitor the emotional state of new mothers and provide them with adequate support during this period of hormonal transition.

In summary, progesterone plays a key role during pregnancy, but its rapid decline postpartum is crucial for the initiation of lactation and the body's return to its pre-gestational state. Understanding these hormonal fluctuations helps us to better understand the challenges of the post-partum period, and to effectively support new mothers.

Melatonin plays a crucial role during pregnancy. Its levels increase during this period and it is mainly secreted at night, peaking between 2 and 4 am. During the day, light inhibits its production. It is therefore essential for the mother to respect this natural rhythm by getting regular sleep and avoiding exposure to blue light in the evening (from computer screens, telephones, etc.).

Melatonin is also involved in the birthing process. It regulates "gap junctions", the connections between endometrial cells, enabling oxytocin to increase the intensity of uterine contractions, thus facilitating labor and delivery.

After birth, melatonin secretion in the mother decreases. In the newborn, however, melatonin production is virtually non-existent. The infant is therefore dependent on its mother's melatonin, which is passed on through breast milk. Breastfeeding therefore plays a crucial role in providing the baby with the melatonin it needs to regulate its circadian rhythm and improve sleep.

Respecting the natural melatonin cycle in the postpartum period not only helps the mother to recover, but also provides an optimal hormonal environment for the newborn's development and well-being.

Cortisol, often referred to as the stress hormone, plays a vital role during pregnancy and postpartum. During pregnancy, cortisol levels rise gradually to help prepare the body for childbirth. It contributes to the maturation of fetal organs and the regulation of maternal metabolism.

After birth, the mother's cortisol levels fluctuate significantly. Cortisol helps to mobilize the energy needed to meet the new demands of motherhood, such as breastfeeding and caring for the newborn. However, high cortisol levels over a prolonged period can be exhausting and contribute to the onset of post-partum depression.

In the newborn, cortisol also plays an important role in adaptation to life outside the womb. Babies are born with relatively high cortisol levels, which help activate their respiratory, circulatory and metabolic systems. However, excessive levels can lead to stress, underlining the importance of a calm, reassuring environment for the infant.

Postpartum stress management and cortisol regulation are crucial to the health of both mother and baby. New mothers are advised to practice relaxation techniques, maintain a regular sleep pattern and seek social support to help moderate cortisol levels. A balanced approach helps to promote optimal recovery and support overall well-being during this transitional period.

Oxytocin, which is produced in large quantities during childbirth, enables contractions and labor. Then, in the post-partum period, its quantity fluctuates, like prolactin, as breastfeeding progresses. It is said to be the hormone of love and maternal attachment.

Oxytocin is produced during the postpartum period by the following stimuli:

During the 9 months of pregnancy, the mother's body gradually changes. And it's not because she's just given birth that her body will immediately return to normal.

The infographic below summarizes the different changes in women and the time it takes to "return to normal".

Marie Messager
Osteopath D.O
Trained in perinatal care
In Versailles - 78