That moment, when a pregnancy strip shows two distinct lines, is a moment of great joy for would-be parents. It confirms their anticipation and hope, and marks the beginning of a woman’s transformation into a mother. She falls in love with her unseen tiny blessing(s) growing inside her belly, and begins a 40-week journey, drawing closer each day to the arrival of their little one.
Pregnancy brings about physical, psychological, and emotional changes in women. The most noticeable changes are the growing belly and weight gain, and the expansion of skin to accommodate the growth of the foetus. For some women, pregnancy brings radiant skin and a rosy complexion. In contrast, for others, the changes in the skin may not be so appealing, due to acne, dark spots (melasma), stretch marks, spider and varicose veins, as well as dry and itchy skin (Soma-Pillay et al., 2016).
During pregnancy, the human body undergoes sudden changes and challenges. However, the skin shows remarkable resilience in adapting to them. As the foetus develops, the uterus grows larger, and so does the belly region. To make room for the growing baby, the skin stretches and expands, causing the breakdown of structural proteins such as collagen and elastin.
Collagen and elastin are two essential proteins primarily found in the skin, which provide structure, strength, and elasticity. During pregnancy, changes in these proteins play a significant role in accompanying the expansion of the skin, especially in the belly region. Pregnancy hormones like estrogen, progesterone, and relaxin increase the production and distribution of collagen and also enhance its flexibility in the skin. Elastin is another protein that significantly contributes to the flexibility of the skin by structurally rearranging along with collagen.
In this article, we shall take a closer look at the resilience of the skin as it stretches itself around a growing foetus, and how it bounces back after the baby is born.
.](/static/b953864e16dbc2a6700a6060fa4bd695/f65ec/skin_structure.png "Anatomy of the skin. Credit: [Wikimedia](https://commons.wikimedia.org/wiki/File:Structure_of_mammalian_skin_and_the_layers_typically_present_in_parchment.png).")
Anatomy of the skin. Credit: Wikimedia.
The skin covers the whole body, providing a range of functions, such as protecting against injury and harmful microorganisms. It is also responsible for our sense of touch, temperature, and pressure, and helps regulate our body temperature through sweat glands. Furthermore, the skin stores fats, lipids, and water to maintain proper hydration levels.
Structurally, the skin is composed of two main layers: the outer layer called the epidermis, and the inner layer called the dermis. The epidermis comprises tightly packed epithelial cells, including keratinocytes that produce keratin, a structural protein that is vital for healthy skin, hair, and nails. The epidermis also contains melanocytes which produce melanin, a pigment which gives its unique colour to the skin, hair, and eyes. Additionally, Langerhans cells are specialized immune cells that help protect the skin from harmful pathogens (Kolarsick et al., 2013).
The dermis consists of a variety of cells and tissues, including blood vessels, nerve endings and sensory receptors that respond to external stimuli, hair follicles and the lymphatic system. In addition, it contains different glands, including sebaceous glands that produce sebum (a body oil) and apocrine glands that produce sweat. However, the majority of the dermal layer is composed of connective tissue that contains cells called fibroblasts. These cells produce fibrous proteins such as collagen and elastin, which are then secreted outside. This complex network of proteins, along with a few other biomolecules present in the extracellular space, forms what is called the extracellular matrix (ECM). This gives the dermis its ability to stretch and provides it with strength, structural support, and elasticity (Watt, 2014).
These two layers are separated by a specialized form of ECM called the basement membrane. The basement membrane plays a vital role in providing structural integrity and support to the skin. It helps maintain elasticity, tensile strength, tissue stiffness, and stability of the skin layers. The basement membrane is composed of a complex network of collagen and elastin fibres, as well as other important biomolecules. Together, these components form a supportive framework that gives the skin its structural integrity (Roig-Rosello and Rousselle, 2020).
During pregnancy, the basement membrane and extracellular matrix components, especially collagen and elastin, work synergistically to allow for controlled stretching of the skin. This contributes to the skin’s ability to stretch while providing a supportive framework.
Collagen is a protein that has a unique structure consisting of three strands tightly wound together in a helix shape. It is composed of small amino acids such as glycine and proline, which give it the ability to provide firm and tight support to the skin. The primary functions of collagen include providing structural support to the connective tissues in the extracellular space, as well as providing tensile strength and resistance to stretching due to its rigidity (Reilly and Lozano, 2021).
Elastin, on the other hand, is a protein that is more elastic and flexible than collagen. Elastin is responsible for the stretching and recoiling functions of the skin. Elastin fibres help to maintain the pressure associated with liquid and airflow in the body [e-book ISBN: 9780128170694].
.](/static/32a32d0b73c50d0236776a8da9044abc/9b601/pregnancy_stretch_marks_skin.jpg "Stretch marks during pregnancy. Credit: [Freepik](https://www.freepik.com/free-photo/pregnant-woman-with-striped-belly_5219516.htm).")
Stretch marks during pregnancy. Credit: Freepik.
The skin of the human body adapts to changes by expanding and contracting. During pregnancy, the body experiences an influx of hormones that increase water and blood flow, thus relaxing the collagen and elastin fibres and reducing their elasticity. This leads to a diminished network of collagen fibres, as the pregnancy progresses. Elastic fibres, on the other hand, lose their tensile strength and resilience, causing the skin to relax and expand with the growing baby (Soma-Pillay et al., 2016).
However, as a result of the rapid growth of the baby, especially in the last trimester, and sudden stretching of the skin, stretch marks (striae) are formed usually on the belly, thighs, and breasts. Stretch marks appear as parallel, narrow red or pink lines, allowing deeper layers of skin to show. In time, stretch marks begin to fade to a silvery, white, or glossy appearance, as the pale fat beneath the skin appears instead of the red blood vessels (Korgavkar and Wang, 2014).
Pregnancy hormones such as estrogen, androgen, and progesterone also cause other harmless changes in the skin, such as the growth of new skin tags, especially under the arms and breasts. Some women may experience face acne due to increased oil production, and dark spots or melasma may also occur due to the rise in melanin pigment. During pregnancy, the mother’s body stores subcutaneous fat to support fetal growth, prepare for childbirth, and feed the newborn, resulting in additional weight gain.
After giving birth, a mother’s body goes through a significant second phase of transition. As the baby is born, the mother’s body shifts from accommodating the baby to providing nutrition through lactation and returning to the pre-pregnancy state. The major physiological changes that occur in the mother’s body to achieve this include the shrinking of the uterus and the elimination of excess fluid through sweat. This process decreases fluid retention and helps in losing weight.
After giving birth, the body’s pregnancy hormones return to their original state. This means that the skin expansion stops, and there is no further tearing of collagen and elastin fibres. As a result, the skin begins to contract and recover through its natural recoiling ability. The skin regains its elasticity from the regenerating elastin fibres. However, it’s important to note that complete restoration to the pre-pregnancy state may not always be possible for everyone. This can vary among individuals and can be influenced by factors such as genetics, age, and the extent of skin stretching during pregnancy.
Although some body changes, such as stretch marks and saggy skin, are common during this time, there are ways to help the body recover and regain its strength. While stretch marks typically fade naturally over time, a mother can take proactive steps to help her skin regain its elasticity and firmness. With the right care and attention, a new mother can feel confident and comfortable in her post-pregnancy body.
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