Mechanism of Normal Labor in Midwifery (Grade A)

Summary:

This section discusses the definitions related to normal labour, including the process of labour itself and terms like “lightening,” “attitude,” “fetal lie,” “fetal presentation,” and “fetal position.” It covers the orientation of the fetus, the presentation of different fetal parts, and the positions in which the fetus can be oriented in relation to the mother’s pelvis. Additionally, the causes of the onset of labour are explained, including hormonal, biochemical, and mechanical factors such as the release of oxytocin, changes in hormone ratios, prostaglandins, and various pressures on the uterus. The recognition of the first stage of labour is outlined, involving signs like blood show, contractions, pain, rupture of membranes, and cervical dilation.

Excerpt:

Mechanism of Normal Labor in Midwifery

Definition of terms related to normal labour:

LABOUR:
 It is described as the process by which the fetus, placenta and membranes are expelled through the birth canal.

LIGHTENING:
 2-3 weeks before the onset of labour, the lower uterine segment expands and allows the fetal head to sink lower; it may engage.
 The fundus no longer crowds the lungs; thus, breathing is easier, and the heart and stomach can function more easily. The woman experiences relief which is known as lightning.

ATTITUDE:
 This refers to the posturing of the joints and the relation of fetal parts to one another.
 The normal fetal attitude when labour begins is with all joints in flexion.

Mechanism of Normal Labor in Midwifery

Fetal Orientation

 Fetal lie
 Fetal presentation
 Fetal position

Fetal lie

• Refers to the relationship of the fetus’s long axis to the mother’s long axis.
• Longitudinal: 99% of all fetuses assume this lie.
• Transverse: long axis of the fetus is perpendicular to the long axis of the mother.
• Result of over-relaxation of the maternal abdominal wall
• Increased risk with multiple pregnancies
• Requires a C-section
• Oblique: the relationship of the spines forms < 45-degree angle.