Labor and Lactation Overview

Labor and Lactation

• Labor is a series of events that expel the fetus from the uterus.
• Parturition or birth is the forcible expulsion of the fetus.
• Labor is comprised of three stages: dilation, expulsion, and placental.
• Before labor, chemical events initiate the process.

Initiation of Labor

• Estrogen levels peak during the last weeks of pregnancy, increasing oxytocin receptors on myometrial cells and suppressing progesterone's inhibitory effects.
• Weak, irregular contractions are called Braxton Hicks contractions (false labor pains).
• Oxytocin and prostaglandins convert false labor into true labor.
• The placenta releases prostaglandins and fetal cells produce oxytocin.
• These hormones cause increasingly powerful contractions.
• A positive feedback mechanism is established: increased emotional/physical stress stimulates oxytocin release, leading to further contractions.
• Fetal fibronectin changes to a lubricant to facilitate expulsion.
• Drugs like oxytocin can accelerate parturition.
• Premature birth can be prevented using drugs that interfere with oxytocin or prostaglandins, e.g,. ibuprofen.

Stages of Labor

• Stage 1 (Dilation):

  • Time from the onset of true labor until the cervix is fully dilated by the baby's head.
  • Initial contractions are weak and regular, occurring 15-30 minutes apart.
  • Later contractions intensify, thin, and dilate the cervix.
  • The longest stage of labor, lasting 6-12 hours or more.
  • Rupture of the fetal membranes ("breaking the water") may occur.

• Stage 2 (Expulsion):

  • From full cervical dilation to delivery/childbirth.
  • Strong uterine contractions occur every 2-3 minutes.
  • Mothers without anesthesia use their abdominal muscles to assist with contractions.
  • Crowning happens when the widest diameter of the baby's head distends the vulva; an episiotomy may assist.
  • This stage lasts approximately 50 minutes to 2 hours.

• Stage 3 (Placental):

  • Accomplished within 30 minutes to 1 hour after the delivery of the infant.
  • Strong uterine contractions expel the placenta and its attached membranes.
  • The placenta and membranes are called the afterbirth.
  • Important to remove all placental fragments to prevent postpartum bleeding.

Labor Complications

• Dystocia: Prolonged and difficult birth, possibly due to a deformed pelvis, maternal fatigue, or fetal brain damage (e.g., cerebral palsy or epilepsy).
• Breech Presentation: Delivery complications if the baby is positioned bottom-first; forceps are often needed.
• Cesarean Section (C-section): Delivery of the infant through an abdominal incision in the abdominal and uterine walls.

Lactation

• Lactation is milk production by the mother's mammary glands.
• Mammary glands are fully developed by the end of the 6th month of pregnancy.
• Why do pregnant women's breasts get bigger? High estrogen and progesterone concentrations cause expansion of duct systems and secretory units in the mammary glands. Additional adipose tissue is deposited.
• Colostrum: Yellowish secretion rich in vitamins, minerals, and proteins; is produced for the first few days post-birth; contains antibiotics to protect the infant.
• Breast Milk: After the first few days, milk production begins. It contains water, proteins, amino acids, lipids, sugars, salts and lysozymes.
• High levels of prolactin suppress FSH and LH release, preventing menstruation and ovulation postpartum. This period is called lactational amenorrhea and is variable, ranging from 3 months to 3 years.

Milk Let-Down Reflex

• Stored mammary gland secretions are released due to a neuro-endocrine reflex.
• Mechanical stimulation of the nipple leads to nerve impulses, triggering the release of oxytocin from the posterior pituitary.
• Oxytocin stimulates myoepithelial cells to contract surrounding alveoli.
• Milk release is called milk let-down or milk ejection.
• The reflex continues for about 1-2 years post-birth.

Advantages of Breast Milk

• Better absorption of fats and iron.
• More efficient metabolism of amino acids.
• Protects against life-threatening infections.
• Contains substances that prevent ulcers.
• Has a natural laxative effect, helping clean the bowels of Meconium.
• Encourages the colonization of beneficial bacteria for vitamin K and some B vitamin production.

Explore the intricate processes involved in labor and lactation. This quiz covers the stages of labor, hormonal influences, and the physiological changes that facilitate childbirth. Test your knowledge on the initiation of labor, the role of hormones, and the feedback mechanisms involved.