Your baby in the birth canal

Definition

During labor and delivery, your baby must pass through your pelvic bones to reach the vaginal opening. The goal is to find the easiest way out. Certain body positions give the baby a smaller shape, which makes it easier for your baby to get through this tight passage.

The best position for the baby to pass through the pelvis is with the head down and the body facing toward the mother's back. This position is called occiput anterior.

Information

Certain terms are used to describe your baby's position and movement through the birth canal.

FETAL STATION

Fetal station refers to where the presenting part is in your pelvis.

In first-time moms, the baby's head may engage by 36 weeks into the pregnancy. However, engagement may happen later in the pregnancy, or even during labor.

FETAL LIE

This refers to how the baby's spine lines up with the mother's spine. Your baby's spine is between his head and tailbone.

Your baby will most often settle into a position in the pelvis before labor begins.

FETAL ATTITUDE

The fetal attitude describes the position of the parts of your baby's body.

The normal fetal attitude is commonly called the fetal position.

Abnormal fetal attitudes include a head that is tilted back, so the brow or the face presents first. Other body parts may be positioned behind the back. When this happens, the presenting part will be larger as it passes through the pelvis. This makes delivery more difficult.

DELIVERY PRESENTATION

Delivery presentation describes the way the baby is positioned to come down the birth canal for delivery.

The best position for your baby inside your uterus at the time of delivery is head down. This is called cephalic presentation.

If your baby is in any position other than head down, your doctor may recommend a cesarean delivery.

Breech presentation is when the baby's bottom is down. Breech presentation occurs about 3% of the time. There are a few types of breech:

The shoulder, arm, or trunk may present first if the fetus is in a transverse lie. This type of presentation occurs less than 1% of the time. Transverse lie is more common when you deliver before your due date, or have twins or triplets.

CARDINAL MOVEMENTS OF LABOR

As your baby passes through the birth canal, the baby's head will change positions. These changes are needed for your baby to fit and move through your pelvis. These movements of your baby's head are called cardinal movements of labor.

Engagement

Descent

Flexion

Internal Rotation

Extension

External Rotation

Expulsion


Review Date: 9/25/2018
Reviewed By: John D. Jacobson, MD, Professor of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda Center for Fertility, Loma Linda, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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