Module 4 Fertilization to Birth

Lesson 3—Hormones and the Birthing Process

Get Focused

Birth is an incredible event. Although birth is not the beginning of your life’s story, it is certainly one of the most important moments in your life. What is your birth story? Do you know what happened around the time of your birth? Was there a birth plan for your delivery? If not, make sure you ask someone who knows how you were born, what your ‘birth’ day was like and the events surrounding this special moment in your life.

Today women have many choices on how to deliver their baby. Birth with a midwife at home, birth with a midwife at a birthing center, birth in a hospital, birthing into water, and many more options are all possibilities when delivering a baby today. No matter what a woman’s birth plan choice is, once the birthing process begins, there is no going back.

Continuation of the species, in humans, occurs at approximately 266 days, at which time gestation ends with the birth of the fetus. For Jane, a few days before her baby was ready to enter the outside world, she felt a sensation that the baby was settling deeper into her pelvis. This sensation is commonly called lightening.

Parturition, or labour (terms given to the birthing process) is divided into 3 stages: the dilation stage, the expulsion stage, and the placental stage. Jane was said to be ‘in labour’ when her cervix was dilated to about 3 cm in diameter, and her uterine contractions lasted for 40 seconds and occurred every 15 to 20 minutes.

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Jane’s labour was controlled by both nerves and hormones, through a positive feedback system. The dilation stage of parturition began as the cervix shortened, contracting up into the uterus. This event helped release the hormone oxytocin from the pituitary’s posterior lobe. The release of oxytocin caused uterine contractions to continue pushing the fetus down toward the cervix.  The cervix continued to stretch, which positively fed back to the posterior pituitary to continue the release of oxytocin.  Her uterine contractions also stimulated the release of prostaglandins, which were also stimulated by positive feedback.

The expulsion stage of parturition consists of the delivery of the fetus. This is the stage in which Jane and John’s baby was actually ‘born’. For this to happen, their baby’s head had to rotate as it moved into the birth canal. Once the head and shoulders of the baby were out of the birth canal, the rest of the body delivered quickly. Soon after delivery, John was able to cut the umbilical cord.  

There are many reasons that a normal vaginal birth may not be possible. When this happens doctors have to resort to a Cesarean section. A C-section, as it is sometimes called, consists of a surgical procedure where an incision is made in the mother’s lower abdomen through to her uterus.

In the placental stage, which in most cases happens within 30 minutes after the baby is delivered, the placenta disengages from the uterus and is expelled from the body. Jane was encouraged to breast-feed as soon after delivery as possible, as this helps shrink the uterus so there is less blood loss.

Lactation, or breast-feeding, occurs when estrogen and progesterone production is suppressed and the anterior pituitary secretes the hormone prolactin. Breast milk production is stimulated by the suckling of the new baby, through nerve endings in the nipple. Nervous stimulation causes oxytocin to be secreted, which acts to cause contractions in the breasts. For the first few days of breast-feeding, Jane produced colostrums, a yellowish liquid that contains antibodies and more protein than breast milk.

Jane and John have had a successful pregnancy and delivery, and now have a brand new healthy baby that has joined their family. To you, their fertility doctor, they are very thankful!

The following focusing questions are addressed in this lesson:

• What triggers the birthing process, and what are the stages of the birthing process?
• What controls lactation?

Module 4: Lesson 3 Assignment

 Once you have completed all of the learning activities for this lesson, complete the online assignment.

Bio30 2.4.3 online assignment

Here is a tutorial video for this lesson that you can watch if it suits your learning style. Bio30 tut#2.4.3 Birth and Lactation

** The Self-Check and Try This questions in this lesson are not marked by the teacher; however answering these questions will help you review important information and build key concepts that may be applied in future lessons. You can respond to these mentally, write out your response, or record your answer in any other way that works for you.