Physiological adaptations of pregnant women: biological dynamics in high-temperature contexts

Pregnancy involves significant physiological modifications, including changes in thermoregulation and metabolism systems. During summer months, exposure to high temperatures represents a risk factor for maternal-fetal homeostatic balance, requiring targeted preventive strategies.

Maternal physiology and risks of hyperthermia during pregnancy

Maternal hyperthermia — defined as an increase in core body temperature above 38°C — can cause ineffective thermoregulation, hyperhidrosis, and osmotic dehydration, compromising placental perfusion and increasing the risk of fetal hypoxia and neurobehavioral damage. Epidemiological studies link exposure to high temperatures with an increase in preterm birth, IUGR, and neurological anomalies (ISS, 2023).

From a physiological perspective, the pregnant woman experiences increased basal metabolism and plasma volume, with reduced thermoregulatory capacity due to changes in the autonomic nervous system and slowed sweating response. Overactivation of the renin-angiotensin-aldosterone system may induce electrolyte imbalances. It is therefore essential to ensure adequate fluid and electrolyte intake, with particular attention to sodium, potassium, and magnesium (Edwards, 2019).

Behavioral measures include avoiding sun exposure during peak hours, wearing breathable clothing, and keeping environments air-conditioned or ventilated. Moderate physical activity, planned during cooler hours, helps reduce heat stress.

From a nutritional point of view, a balanced intake of antioxidant micronutrients and fluids is necessary to counteract oxidative stress and prevent metabolic disorders. Clinical monitoring should include evaluation of blood pressure, body weight, fluid balance, and kidney function, especially in women with comorbidities such as preeclampsia or gestational diabetes (Chen, 2020).

 

Table 1. Nutritional advice for pregnant women in summer

Food category Specific recommendations Main benefits
Fresh fruits and vegetables At least 5 servings per day, rich in vitamins and antioxidants Counteracts oxidative stress, hydration
Lean proteins Blue fish, chicken, legumes  Supports fetal growth and tissue repair
Whole grains  Whole wheat bread, pasta, brown rice Maintains stable glycemic control
Liquids Natural water, mineral waters rich in electrolytes   Prevents dehydration and electrolyte imbalances
Foods to limit Foods high in refined sugars, caffeine Avoids dehydration and glycemic fluctuations
Additional recommendations for pregnant women during summer
1. Balanced and nutrient-rich diet
During the summer, it is essential for pregnant women to follow a balanced diet rich in fresh fruits and vegetables to ensure adequate intake of vitamins, minerals, and antioxidants, which are key to counteracting heat-induced oxidative stress. Intake of foods rich in folate, iron, and calcium should be maintained, while favoring light and easily digestible meals to avoid typical summer gastrointestinal issues such as nausea and reflux. Choosing low-glycemic-index foods helps stabilize blood glucose levels and prevent glycemic spikes (ISS, 2023).
2. Proper hydration and electrolyte balance
Hydration is one of the most critical aspects for pregnant women in summer. Increased sweating requires higher consumption of natural water and electrolyte-rich beverages (such as rehydration solutions or balanced mineral waters) to prevent dehydration and electrolyte imbalance. It is advisable to avoid drinks containing caffeine or refined sugars, as they can worsen dehydration. Monitoring urination frequency and color is a simple and immediate way to assess hydration status.
3. Sun protection and prevention of sunburn
Direct sun exposure should be limited, especially during peak hours, to prevent heatstroke and skin damage. The use of high-protection sunscreens (SPF ≥ 30) formulated for sensitive and pregnant skin is recommended, along with wide-brimmed hats and protective sunglasses. Skin protection is also important to prevent pigmentation changes typical of pregnancy, such as melasma, which can be exacerbated by UV exposure (Gagnon, 2017).
4. Management of physical activity and rest
Physical activity remains important for maternal health, but in summer it must be planned to avoid excessive heat exposure. Exercise should be done during the cooler hours, with frequent breaks and in ventilated environments. Rest is essential to recover from heat stress; sleeping in cool, darkened rooms helps preserve sleep quality, reducing the risk of fatigue and irritability (Lankisch, 2018).
5. Clinical monitoring and prevention of complications
In addition to routine checkups, pregnant women should be monitored for signs of dehydration, pregnancy-induced hypertension, and electrolyte imbalances, which are more frequent during hot weather. Regular evaluation of blood pressure, urination, and blood parameters (electrolytes, urea, creatinine) is crucial, especially in high-risk pregnancies. In the presence of symptoms such as dizziness, severe headache, or sudden swelling, it is essential to consult a doctor promptly.

The summer season requires particular attention to the physiological and metabolic needs of pregnant women. A multidimensional approach that includes a balanced diet, consistent hydration, proper sun protection, moderate physical activity, and regular clinical monitoring is essential to ensure an optimal environment for maintaining maternal-fetal homeostasis. Implementing these strategies helps minimize heat-stress-related risks and promotes maternal-fetal health, ensuring a safe and favorable pregnancy journey even in the most challenging environmental conditions.

The journey of pregnancy: every moment is unique

Pregnancy represents a complex and extraordinary process of biological, psychological, and relational transformation. Each pregnancy is a unique experience, both physiologically and emotionally.

Weeks 4–6: early adaptations and initial changes

In the first weeks of pregnancy, the changes are mainly internal and often not externally visible. Early signs include mastodynia, a sensation of abdominal bloating, and fatigue, resulting from increased progesterone levels and vascular remodeling. The female body begins to silently adapt to host the embryo, triggering complex processes such as increased cardiac output, expansion of plasma volume, and the onset of uterine changes.

This is the phase in which the foundations of bonding with the unborn child are laid, even though emotional recognition of the pregnancy often occurs later.

From week 12: pregnancy becomes visible

Around the end of the first trimester, the uterine volume increases more noticeably, making the pregnancy perceptible even externally. The growth of the uterine fundus changes the abdominal silhouette, while the breasts continue to prepare for lactation, increasing in volume and vascularization.

These physical changes often require adaptations in clothing and daily routines. At this stage, the use of elasticizing creams and comfortable clothing is helpful, as well as starting a health education program for the prevention of postural and venous disorders.

From week 20: fetal development and maternal somatic adaptation

At mid-pregnancy, the uterus reaches the level of the navel, and the mother may begin to feel the first fetal movements (quickening). The changes become more pronounced: the lumbar curve deepens, venous pressure may increase, and body weight begins to grow significantly.

Obstetric support at this stage is crucial to monitor uterine growth and maternal-fetal well-being, as well as to educate the expectant mother about signs and symptoms not to be underestimated (e.g., edema, headaches, visual disturbances). It is also the ideal time to introduce concepts of childbirth and breastfeeding preparation.

Between weeks 30 and 35: slowing down and active waiting

As the due date approaches, the uterus occupies more space in the abdominal cavity, altering posture and affecting breathing and sleep quality. Joint laxity increases, especially in the pelvic area, due to the action of relaxin. Many women experience discomfort related to the uterine weight, such as lower back pain, sciatica, and fatigue.

The role of the midwife during this phase is fundamental to propose non-pharmacological relief strategies (gentle movement, postural exercises, massages) and to provide emotional support in preparing for childbirth, also through relaxation and breathing techniques.

From week 36 to 40: the body prepares for labor

In the final days of pregnancy, a progressive descent of the presenting part into the pelvis (fetal descent) can be observed, which may relieve diaphragmatic pressure but increase pelvic pressure. Braxton Hicks contractions may become more frequent, and the body begins to show clear signs of preparing for labor.

Professional support during this period should focus on reassurance, clinical monitoring of maternal and fetal health, and the promotion of emotional well-being, by normalizing anxieties and expectations related to the imminent birth.

Pregnancy is a complex physiological process, characterized by a sequence of biological, psychological, and social adaptations that involve the woman in her entirety. Each gestational phase entails significant changes that, while physiological, require careful observation and understanding.
Attention to bodily signals, listening to emotional needs, and enhancing individual resources are essential to fostering a positive pregnancy experience. In this context, informed and respectful support from health professionals plays a crucial role in sustaining the physiology of pregnancy, recognizing and valuing the uniqueness of each experience. This approach not only facilitates adaptation to the intrinsic changes of pregnancy but also promotes the long-term well-being of the mother-child dyad.