Physiological changes during pregnancy

Overview of Physiological Changes During Pregnancy

Pregnancy brings extensive physiological changes across multiple body systems. These adaptations are essential to support fetal development, maternal health, and the demands of labor and delivery. Most changes are regulated by hormones such as estrogen, progesterone, human chorionic gonadotropin (hCG), and prolactin. Below is a system-wise explanation of these changes.

Physiological Changes
1– Cardiovascular Changes
2– Respiratory Changes
3– Renal and Urinary System Changes
4– Gastrointestinal Changes
5– Endocrine and Metabolic Changes
6– Hematologic Changes
7– Musculoskeletal and Postural Changes
8– Skin and Pigmentation Changes
9– Breast and Reproductive System Changes

1. Cardiovascular Changes

Cardiac output increases by up to 50% due to elevated heart rate and stroke volume. Blood volume expands by 30–50% leading to physiological anemia. Systemic vascular resistance decreases, often lowering blood pressure in early pregnancy. A systolic murmur may be heard, and there is increased risk of varicose veins and edema due to venous stasis.

2. Respiratory Changes

Progesterone stimulates increased respiratory drive, leading to higher tidal volume and minute ventilation. Oxygen consumption increases by 20%. Although respiratory rate remains stable, mild respiratory alkalosis may occur. The diaphragm elevates due to uterine enlargement, but lung function is generally preserved.

3. Renal and Urinary System Changes

Renal blood flow and glomerular filtration rate increase by 40–60%, enhancing clearance of waste products. Ureters and renal pelvis dilate, especially on the right, leading to physiological hydronephrosis. There is increased urinary frequency and a higher risk of urinary tract infections.

4. Gastrointestinal Changes

Hormonal effects, especially from progesterone, slow gastrointestinal motility, leading to constipation and reflux. Nausea and vomiting (morning sickness) are common in the first trimester. Gallbladder motility is reduced, increasing the risk of gallstones.

5. Endocrine and Metabolic Changes

There is increased activity of the thyroid and adrenal glands. Insulin resistance develops in the second half of pregnancy, influenced by placental hormones, potentially leading to gestational diabetes. Basal metabolic rate rises to meet fetal and maternal energy demands.

6. Hematologic Changes

Red cell mass increases, but plasma volume rises more significantly, causing dilutional (physiological) anemia. White blood cell counts may be elevated. There is a hypercoagulable state due to increased clotting factors, reducing hemorrhage risk but increasing thromboembolic risk.

7. Musculoskeletal and Postural Changes

Relaxin and progesterone cause ligamentous laxity, especially in the pelvis. The growing uterus shifts the center of gravity, causing lumbar lordosis and back pain. These adaptations prepare the body for delivery but may result in discomfort.

8. Skin and Pigmentation Changes

Estrogen and melanocyte-stimulating hormone cause hyperpigmentation, including linea nigra and melasma. Stretch marks (striae gravidarum) may appear due to rapid skin stretching. Increased blood flow may cause skin warmth and redness.

9. Breast and Reproductive System Changes

Breast enlargement, tenderness, and darkening of the areolae occur due to hormonal stimulation. Colostrum may be produced in late pregnancy. The uterus grows exponentially, and the cervix softens (Goodell’s sign) and becomes more vascular (Chadwick’s sign).

Physiological changes during pregnancy

Introduction of fetal sonography

Fetal ultrasound is a widely used imaging technique that employs high-frequency sound waves to create images of a developing fetus within the uterus. It is a non-invasive, safe, and painless procedure that provides crucial information about fetal development, maternal health, and potential complications during pregnancy

Introduction
1– Purpose of Fetal Ultrasound
2– Types of Fetal Ultrasound
3– When is Fetal Ultrasound Performed?
4– Safety and Considerations
5– History and evaluation of fetal ultrasound
6– Sefty and bioeffectsof Fetal; Ultrasound

1. Purpose of Fetal Ultrasound

• Fetal ultrasound serves multiple purposes, including:
• Confirming pregnancy and estimating the gestational age.
• Assessing fetal growth and development to ensure proper progress.
• Detecting congenital anomalies or structural abnormalities.
• Determining fetal position in preparation for delivery.
• Monitoring amniotic fluid levels and placental health.
• Assessing multiple pregnancies, such as twins or triplets.

2. Types of Fetal Ultrasound

• Transabdominal Ultrasound – A common method where a probe is moved over the mother's abdomen using a gel to enhance sound wave transmission.
• Transvaginal Ultrasound – Used in early pregnancy or when a clearer image is needed, where a probe is inserted into the vagina for better visualization.
• Doppler Ultrasound – Assesses blood flow in the umbilical cord, placenta, and fetal organs.
• 3D and 4D Ultrasound – Provides detailed images of the fetus, often used for detecting facial and structural abnormalities.

3. When is Fetal Ultrasound Performed?

• First Trimester (6-12 weeks) – To confirm pregnancy, check for heartbeat, and estimate due date.
• Second Trimester (18-22 weeks) – Detailed anatomy scan to evaluate fetal development and check for abnormalities.
• Third Trimester (28+ weeks) – To monitor fetal growth, positioning, and overall health.

4. Safety and Considerations

Fetal ultrasound is considered safe with no known harmful effects when performed by trained professionals. However, it should only be conducted when medically necessary to avoid unnecessary exposure.

5.History and Evaluation of Fetal Ultrasound

Introduction Ultrasound has revolutionized the field of obstetrics, offering non-invasive, real-time imaging to monitor fetal development. The journey of ultrasound in obstetrics spans over several decades, evolving from rudimentary techniques to advanced 3D and 4D imaging. This document outlines the history and key advancements in obstetric ultrasound.
Early Developments (1940s-1950s) The origins of ultrasound in medical diagnostics can be traced back to sonar technology used during World War II. In the late 1940s and early 1950s, pioneers such as Ian Donald, John MacVicar, and Tom Brown began exploring ultrasound for medical applications. Ian Donald, in particular, played a crucial role in adapting ultrasound for obstetrics, demonstrating its potential in detecting fetal abnormalities and assessing pregnancy-related conditions.
Introduction to Obstetric Ultrasound (1960s-1970s) By the 1960s, ultrasound had started to gain recognition as a valuable tool in obstetrics. The development of A-mode (amplitude mode) and B-mode (brightness mode) ultrasound allowed for improved imaging of the fetus. In 1958, Donald and MacVicar published a groundbreaking paper demonstrating the use of ultrasound to diagnose pregnancy and detect fetal anomalies.
During the 1970s, real-time ultrasound imaging became available, allowing continuous visualization of the fetus. This advancement significantly improved prenatal care by enabling more accurate fetal assessments, including the detection of multiple pregnancies and fetal growth monitoring.
Technological Advancements (1980s-1990s) The 1980s witnessed significant advancements in ultrasound technology, including the introduction of Doppler ultrasound, which allowed for the assessment of blood flow in the placenta and umbilical cord. This innovation was instrumental in identifying conditions such as intrauterine growth restriction (IUGR) and fetal distress.
In the 1990s, 3D ultrasound technology emerged, offering more detailed images of the fetus. This advancement improved the ability to detect congenital anomalies, providing expectant parents and healthcare professionals with enhanced visualization of fetal structures.
Modern Ultrasound (2000s-Present) The 21st century has seen remarkable progress in obstetric ultrasound, including the advent of 4D ultrasound, which enables real-time three-dimensional imaging of the fetus. High-definition ultrasound, artificial intelligence integration, and portable ultrasound devices have further refined the accuracy and accessibility of fetal imaging.
Ultrasound has also become an essential tool in prenatal screening programs, aiding in the early detection of chromosomal abnormalities such as Down syndrome through nuchal translucency scans. Additionally, advancements in contrast-enhanced and elastography ultrasound are opening new avenues for fetal assessment.

6. Safety and Bioeffects of Fetal Ultrasound

Fetal ultrasound is widely used in prenatal care to monitor the development of the fetus and detect any potential complications. While it is considered a safe and non-invasive imaging technique, concerns about potential bioeffects—especially with prolonged or high-intensity exposure—have been raised.

i. Safety of Fetal Ultrasound

Ultrasound imaging relies on high-frequency sound waves to produce images of the fetus. It does not involve ionizing radiation (such as X-rays or CT scans), making it a safer alternative for fetal monitoring. The American Institute of Ultrasound in Medicine (AIUM), the Food and Drug Administration (FDA), and the World Health Organization (WHO) consider diagnostic ultrasound safe when used appropriately by trained professionals.

ii. Potential Bioeffects of Fetal Ultrasound

Although no confirmed harmful effects have been established in humans, ultrasound waves can interact with biological tissues in two primary ways:

A. Thermal Effects

• Ultrasound waves cause slight heating of tissues as sound energy is absorbed.
• The thermal index (TI) is a key safety parameter, representing the potential for temperature rise.
• Studies suggest that a temperature increase of more than 1.5°C for prolonged periods could pose risks to fetal development, but routine diagnostic ultrasound is unlikely to reach this threshold.

B. Mechanical Effects (Cavitation)

• Ultrasound waves create rapid pressure changes, which may lead to cavitation—formation of tiny gas bubbles in biological fluids
• Although cavitation is a concern in laboratory settings, it is not considered a significant risk during routine fetal ultrasound since human tissues typically do not contain gas bubbles in large quantities.
iii. Guidelines for Safe Use

• To minimize any potential risks, international regulatory bodies have established guidelines:
• Use only when medically necessary: Ultrasound should not be used solely for non-medical purposes, such as "keepsake" videos.
• Limit exposure time: The principle of ALARA (As Low As Reasonably Achievable) should be followed to reduce unnecessary exposure.
• Monitor safety indices: The thermal index (TI) and mechanical index (MI) should be kept within safe limits, particularly in early pregnancy when fetal tissues are more sensitive.
• Use Doppler ultrasound with caution: Doppler imaging, which uses higher energy levels, should be reserved for specific medical indications and used minimally in the first trimester.
iv. Research and Controversies

• Some animal studies suggest potential developmental effects with prolonged or high-intensity ultrasound exposure, but these conditions do not reflect typical clinical use in humans.
• Epidemiological studies in humans have not found definitive evidence linking diagnostic ultrasound to adverse fetal outcomes such as low birth weight, speech delays, or neurodevelopmental issues.
• Ongoing research continues to assess long-term effects, particularly as newer, more advanced ultrasound technologies emerge.



Introduction of fetal sonography