You are NOT crazy! When you feel like crying because you’re overwhelmingly happy and you feel so angry you start laughing – that is totes normal! Well at least it’s completely out of your control. The massive shift in hormones is very real during pregnancy and it does not only mess with your mood but can affect how you workout and what is safe for you and your baby.

Understanding the effect certain hormones have on the structures of the body - both skeletal and muscular -  will go a long way to explaining the physical and physiological changes that you are experiencing.

Below is a list of the most important hormones and the changes in their levels that occur over the 40 weeks of pregnancy.


  • Relaxin is produced by the placenta - the goal of this hormone is to soften the cervix and tissues of the birth canal in preparation for childbirth
  • Unfortunately this muscle laxity is not localized to the birth canal, and along with progesterone, softens ligaments throughout the entire body
  • This global softening of muscles can cause damaging joint instability
  • BLP focuses on countering these effects with stability exercises, and recommend using caution when stretching - it’s easy to go “too far” because of the joint laxity and harm the joint capsule


  • Estrogen is usually produced by the ovaries, but during your pregnancy is produced by the placenta
  • It strengthens and prepares the womb for implantation of the fertilized egg
  • It prepares the breasts for breastfeeding by enlarging the nipples and encouraging the development of milk glands
  • It regulates the development of the fetus and maintains the endometrium during pregnancy


  • Progesterone stimulates the thickening of the uterine lining in anticipation of implantation of a fertilized egg
  • It relaxes the smooth muscle of the uterus to prevent muscle contractions that could otherwise trigger miscarriage
  • It inhabits the production of monoamine oxidase (MAO) in the brain, which usually produces depressive reactions. This is one of the big reasons you feel almost euphoric during pregnancy, particularly in your 2nd trimester when the exhaustion and sickness of the first trimester has passed. This massive shift in progesterone can have the opposite effect and pregnancy depression can occur
  • It also increases body temperature, helps in the production of breast milk, dilates blood vessels and relaxes muscle in the bladder, bowel and veins so that they are more flexible 


  • Oxytocin is the pleasure or ‘love’ hormone of the body and is naturally secreted when you have sex
  • It causes contractions of the uterus and stimulates the labor process - continuing to be released throughout delivery


  • Pitocin is the synthetic form of Oxytocin, used to induce labor


  • This hormone is only produced during pregnancy - first by the ovaries and later by the placenta
  • The high HCG hormone levels found in maternal plasma and urine during the first trimester may contribute to causing nausea and vomiting - morning sickness


  • This hormone, produced by the placenta, ensures proper fetal development and plays a role in stimulating milk glands in the breasts in anticipation of breastfeeding


    • This hormone blocks the reception of pain and enhances mood during labor


    • Adrenaline is a stress-response hormone produced by the adrenal glands that help the woman gear up for labor
    • When there is an over production of adrenaline it can infact inhibit the progression of labor by inhibiting the production of oxytocin


    • This hormone softens and thins the cervix in preparation for labor and plays a role in fetal growth