Are you nearing your due date? Is the thought of delivery making you nervous? Or have you just entered the second trimester and the clumsiness phase? Is pain that you experience in the joints and lower back worrying you? There is one answer for all these problems – relaxin hormone. This hormone helps in easy vaginal delivery. This same hormone also causes pain and makes the pregnant women clumsy. Continue reading to know more about this hormone.
relaxin hormone in pregnancy

What Is Relaxin Hormone?

Relaxin is a protein-based hormone usually secreted by the corpus luteum (which is a hormone-producing structure) in the ovary. Relaxin hormone is found both in men and non- pregnant women. In men, the prostate gland secretes the relaxin hormone in their bodies. In non- pregnant women, the corpus luteum in the ovary alone produces the relaxin hormone. However during pregnancy, the quantity produced in the ovary cannot meet the demand of this hormone so the placenta and the lining of the uterus also start producing this hormone.
In both pregnant and non-pregnant women relaxin hormone rises to a highest within 14 days of ovulation, and then declines in the absence of pregnancy, resulting in menstruation.
During pregnancy, the levels of relaxin hormone considerably rise and pregnant women have 10 times the normal amount of relaxin hormone in their bodies.

Role Of Relaxin Hormone During Pregnancy

Actually, the role of relaxin hormone in pregnancy starts way before conception. The relaxin hormone plays an important role during pregnancy in following ways:

  • Preparing the uterus for pregnancy: The levels of relaxin increases after ovulation. At this time, in order to prepare the uterus for possible pregnancy, the hormone-
    • Prepares the uterine lining to facilitate implantation
    • Relaxes the uterine wall to prevent contractions, which can hinder with the implantation of a fertilized egg
    • However, if fertilization does not take place, the relaxin levels drop to normal
  • The role of relaxin during the first trimester of pregnancy: During the early weeks of pregnancy, the relaxin levels are higher and this helps in successful implantation of fertilized egg into the uterine wall
  • Relaxing intrauterine membrane: During pregnancy the relaxin hormone prevents the possible contractions of the intrauterine membrane. In this way it helps in sustaining pregnancy and avoiding premature childbirth
  • Relaxes arteries: The blood volume doubles in women during pregnancy in order to meet the increased demand of oxygen and nutrients of the fetus as well as the mother. The relaxin hormone relaxes the blood vessels to handle the increased blood volume. This way, relaxin hormone prevents the possibility of high blood pressure
  • Helping with parturition: Parturition refers to the process of delivering baby and placenta through the vagina. During the last trimester, relaxin prompts the rupture of the membranes surrounding the fetus. It also stimulates the growth, opening and softening of the cervix and vagina and aid the process of childbirth. Relaxin hormone also relaxes the ligaments at the front of the pelvis to minimize the effort of delivery
  • Helping with mammary gland development: During the second half of pregnancy, the relaxin hormone helps with the development of mammary gland making it ready for the upcoming lactation period
  • Stretching of abdominal muscle and rib cage: In course of pregnancy, the abdominal muscles are stretched to accommodate the growing uterus. The ribcage is also stretched to balance the pressure applied by the growing uterus on the diaphragm. Both of this is possible due to the increased level of relaxin hormone

Pregnancy and relaxin hormone

How Does The Relaxin Hormone Make Joints Unstable During Pregnancy?

Collagen is the main part of the connective tissue found in ligaments, cartilages and tendons. Ligament which is made up of this connective tissue, determines the stability of the joints. The relaxin hormone increases the water content of the collagen fiber which is the main part of connective tissue. This results in increasing the elasticity of the ligament. Thus, when otherwise inelastic ligament becomes more flexible than normal, the joints tend to lose their stability.

Side Effects Of Relaxin Hormone During Pregnancy

The same qualities of the relaxin hormone that helps with pregnancy, delivery and lactation have a flip side too. Some of the side effects of relaxin hormone during pregnancy are:

  • Back pain: The relaxing property of the hormone relaxin affects the ligaments of the spine. During pregnancy, just like other ligaments in the body, the ligament of spine also becomes more elastic and less stable. This makes the expecting mother more susceptible to the back pain
  • Pelvic Girdle Pain: The relaxin hormone often tampers with the pelvic girdle structure which is made up of lot of joints of legs, hips etc. As a result, all the ligaments in the joints become more elastic and loose stability. This can often cause pelvic girdle pain during pregnancy
  • Increased risk of injury: During pregnancy, especially during the last trimester, the overly stretched muscle (because of the act of relaxin hormone) increases the chance of injury in the pregnant women as they become more wobbly and unsteady due to the increased levels of relaxin hormone

Although relaxin hormone has its side effects but this hormone is important to make the birth process easier. So, the pregnant women should take extra care of their posture during pregnancy, especially during the first and the third trimesters, when relaxin hormone is at its peak in the body.