The structured physical examination of a pregnant abdomen is a standardized process used to systematically track the progress of gestation. This comprehensive assessment monitors the growth and well-being of the fetus, confirms the accuracy of estimated due dates, and identifies potential risks. The detailed description resulting from this exam is recorded to ensure continuity of care, allowing providers to compare findings over time and make informed clinical decisions.
Visual Assessment and Measuring Growth
The first step involves a careful visual assessment, or inspection, noting descriptive features of the skin and overall shape. The provider observes for common skin changes due to hormonal shifts and physical stretching. These often include striae gravidarum (stretch marks) which appear reddish or purple when new and silvery-white when older.
Another frequent observation is the linea nigra, a dark vertical line of hyperpigmentation that runs along the midline of the abdomen, typically from the pubic bone toward the umbilicus. Any visible surgical scars, such as those from a previous C-section, are also noted. In later stages, the provider may document visible fetal movement beneath the skin’s surface.
The most standardized part of the physical exam is the measurement of the uterus’s size, known as symphysis-fundal height (SFH). This measurement is taken with a flexible tape measure from the top of the pubic symphysis bone, over the curve of the abdomen, to the highest point of the uterus, called the fundus. The resulting distance is recorded in centimeters.
During the middle trimester (approximately 16 to 36 weeks), the fundal height in centimeters generally correlates closely to the number of weeks of gestation, often being within two centimeters of the gestational age. For example, 28 centimeters suggests a pregnancy of around 28 weeks. This systematic measurement is a reliable screening tool for monitoring fetal growth.
A measurement significantly smaller than expected may suggest a fetus who is Small for Gestational Age (SGA) or conditions like low amniotic fluid. Conversely, a measurement much larger than expected could indicate a Large for Gestational Age (LGA) fetus, a multiple gestation, or excess amniotic fluid. Any deviation prompts further investigation, such as an ultrasound.
Mapping the Baby’s Position
Beyond measuring the size of the uterus, the physical exam uses systematic palpation to determine the orientation of the fetus inside the womb. This process describes the fetal lie, presentation, position, and engagement. Determining these factors is fundamental to anticipating the safest mode of delivery.
Fetal Lie
Fetal lie describes the relationship between the long axis of the fetus and the long axis of the mother. A longitudinal lie (baby positioned vertically) is the most common orientation. Less common are a transverse lie (baby lying horizontally) and an oblique lie (a diagonal, often unstable, position).
Fetal Presentation
Fetal presentation identifies the part of the fetus closest to the mother’s pelvic inlet that would enter the birth canal first. The most frequent presentation is cephalic, or head-first. Cephalic presentation is further classified, with vertex being the most common, where the head is fully flexed.
An alternative is a breech presentation, where the buttocks or feet are presenting first. Breech presentations are categorized by the exact position of the legs, such as frank breech (hips flexed, knees extended), complete breech (hips and knees flexed), or footling breech (one or both feet presenting). The least common is shoulder presentation, which occurs with a transverse fetal lie.
Fetal Position
Fetal position describes the relationship of a specific point on the presenting part to the four quadrants of the mother’s pelvis. This is documented using a three-letter abbreviation system. The first letter indicates the side of the maternal pelvis (Right or Left). The second letter specifies the presenting landmark, such as the occiput (O) for vertex or the sacrum (S) for breech.
The final letter indicates whether that landmark is facing the mother’s anterior (A), posterior (P), or transverse (T) pelvis. For example, a favorable position is LOA (Left Occiput Anterior), meaning the back of the baby’s head is facing the mother’s left front side. Conversely, a position like ROP (Right Occiput Posterior) can sometimes lead to a longer labor.
Fetal Engagement
Fetal engagement describes how far the presenting part has descended into the bony pelvis. The presenting part is considered engaged when its widest diameter has passed through the pelvic inlet. Before engagement, the presenting part is often described as floating or ballottable, meaning it can be easily pushed out.
Engagement is often documented in fifths, indicating how much of the presenting part is still palpable above the pelvic brim. It can also be documented by station, which uses the mother’s ischial spines as a zero reference point. A presenting part at a station of zero is considered engaged.
Documenting Fetal Well-being
The last phase focuses on documenting direct indicators of the baby’s health status. A primary measure of well-being is the assessment of Fetal Heart Tones (FHT). The fetal heart rate is auscultated using a handheld Doppler device or a fetoscope.
The normal range for the fetal heart rate is between 110 and 160 beats per minute (bpm). The provider documents the rate and rhythm, noting the precise location on the mother’s abdomen where the strongest tone was heard, usually over the baby’s back.
Fetal activity is another important descriptive element. The provider records any Fetal Movement (FM) felt during the palpation portion of the exam. Documentation also includes the mother’s subjective report of fetal activity, often called “quickening” or “kick counts.” A consistent pattern of movement is a reassuring sign of fetal health.
Finally, the provider documents related findings concerning the maternal status. This includes noting the presence or absence of uterine contractions, which are felt by placing hands on the abdomen. Any areas of tenderness or rigidity are also recorded, as these may signal underlying complications.