External obstetric examination maneuvers
Four classical external examination maneuvers are used to determine the position of the fetus within the uterine cavity.
The second maneuver aims to determine the fetal position. The physician moves their hands from the uterine fundus to its lateral walls (down to the level of the navel and below) and gently presses with the palms. The fetal back is palpated as a wide, curved surface, while the small parts (arms and legs) are felt as mobile protuberances on the opposite side. In multiparous women, small parts are palpated significantly easier due to laxity of the abdominal wall. The position is established by the back: if it is directed to the left, it is the first position; if to the right, it is the second position. Uterine excitability (its tension in response to touch) is also assessed during palpation.
The third maneuver helps determine the presenting part (head or buttocks) and its relation to the pelvic inlet. The physician grasps the presenting part with one hand (usually the right) and makes gentle side-to-side movements. If the part is above the pelvic inlet, it is considered mobile; if in the inlet or deeper, it is immobile.
The fourth maneuver refines the data from the third. The physician faces the pregnant woman's feet, places palms on both sides of the lower uterus, and inserts fingers between the presenting part and the pelvic inlet. This maneuver allows assessment of the head dimensions, the density of the cranial bones, as well as the localization of the occiput, forehead, and chin. For example, if the occiput is directed to the left and anteriorly, a first position, anterior variety is diagnosed.
Assessment of head engagement and fluid volume
An important stage is determining the depth of the fetal head. The physician performs sliding finger movements along the head toward themselves:
- High floating: the head is mobile above the inlet, fingers can be placed under it.
- At the inlet by a small segment: the sliding hands diverge.
- At the inlet by a large segment (or deeper): the sliding hands converge.
- In the pelvic cavity: the head completely fills the cavity and is not palpable by external maneuvers.
The head is also characterized by the ballottement sign: if the palms are firmly pressed against the lateral parts of the head and a push is made with the right hand, the head bounces to the left and transmits an impulse to the left hand.
The amount of amniotic fluid is assessed by the fluctuation sign. A light tap with one hand on the uterine wall is transmitted through the fluid medium and clearly perceived by the investigator's opposite hand.
Assessment of fetal cardiac activity
Heart rate is the most accurate and objective indicator of fetal condition in the antenatal and intranatal periods. The main method remains auscultation using an obstetric stethoscope.
During auscultation, the physician differentiates fetal heart tones from maternal body sounds (abdominal aorta beating, "blowing" uterine murmurs in large vessels, irregular bowel sounds). Fetal tones begin to be heard from the second half of pregnancy and become louder as gestational age increases. Usually, they are best heard on the side of the back. An exception is face presentation (maximal head extension), in which the chest lies closer to the uterine wall, and the sound is clearer on the chest side.
Auscultation topography depends on the fetal position:
- Cephalic presentation: below the navel (to the left in the first position, to the right in the second).
- Breech presentation: at or above the navel level.
- Transverse lie: at the navel level, closer to the head.
During labor, as the head descends into the pelvic cavity, the point of best auscultation shifts closer to the symphysis along the midline of the abdomen. In multiple pregnancies, the heartbeat is clearly identified in several different parts of the uterus.
Instrumental methods include cardiotocography (CTG) and indirect fetal ECG. ECG is usually performed after the 32nd week of pregnancy: electrodes are placed on the mother's anterior abdominal wall, and a neutral electrode is placed on the thigh. Normally, the ventricular QRS complex is clearly visible on the fetal cardiogram, and sometimes the P wave is registered.
An easy way to remember fetal positions: "First is Left, Second is Right". Association: we read text from left to right, so the left side is number one (first position) and the right side is number two (second position).
Class and exam questions
How to distinguish fetal heart rate from maternal pulse during auscultation?
Maternal murmurs, such as the beating of the abdominal aorta or pulsation of uterine vessels, are always synchronous with the woman's own pulse. Fetal heart tones have their own independent and faster rhythm.
Why are small fetal parts easier to palpate in multiparous women?
This clinical feature is associated with physiological laxity of the anterior abdominal wall and reduced tone of the uterine musculature that occur after previous pregnancies.
How does the point of auscultation change during the course of labor?
As the fetal head descends into the pelvic cavity and the moment of birth approaches, the heartbeat begins to be heard much lower—closer to the symphysis, almost along the midline of the abdomen.
What else to study on this topic
- Technique of performing the first external obstetric examination maneuver
- Cardiotocography (CTG) as a method for assessing fetal condition
- Direct fetal electrocardiography during labor
- Determination of fetal variety (anterior and posterior) according to the relation of the occiput to the back
- Features of palpation and auscultation in fetal face presentation
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