When is relaxin released during pregnancy?

You might be wondering What’s the purpose of this hormone. As the name suggests, relaxin’s primary function is to relax your muscles and ligaments, making room for the development of your baby and making it easier for the hips body to expand enough to deliver. Relaxin isn’t the only hormone in a woman’s reproductive system that has this role, however.

Here are some of the effects are attributed to relaxin:

• Helps in the implantation of the fetus in the uterus;
• Helps in placenta growth;
• Prevents premature labour by stopping contractions;
• Allows the uterus to expand to accommodate the growing placenta and fetus by relaxing intrauterine ligaments.
• Relaxes arteries to accommodate a 30-50% increase in blood volume so the blood pressure does not spike.

Relaxin During The Menstrual Cycle

As far as many women are concerned, their menstrual cycle begins and ends with their monthly period. However, the menstrual cycle is actually composed of two phases: Follicular (proliferative) and Luteal (secretory). Your hormones are busy working during both of them to prepare for a baby.

• The Follicular Phase
  The follicular phase is the initial part of the menstrual cycle. This stage begins on the first day of your cycle and continues until ovulation. Ovulation usually happens around day 14, although it varies depending on the duration of a woman’s cycle.
  When your body produces hormones that encourage egg growth and development in the ovaries, you are in the follicular period. When an egg matures, it is released by the ovary in the expectation of being fertilized, a step referred to as ovulation.
  Relaxin plays a small role throughout the follicular phase. Throughout this half of your menstrual cycle, the primary hormones are gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), estrogen, and luteinizing hormone (LH). What happens after the egg is released affects the role relaxin plays in the following stage of your cycle.

• The Luteal Phase
  This phase starts on the day after ovulation and lasts until your next period arrives. The luteal phase lasts 12-16 days in most women. Your hormones cooperate throughout this period to prepare your body for a probable pregnancy.
  The egg that the ovary releases remains behind an empty follicle known as the corpus luteum. The corpus luteum starts to release progesterone, which combines with relaxin to thicken your uterine lining and aid in the implanting of the fertilized egg.
  If the sperm fertilizes the egg, your progesterone and relaxin levels will surge. Progesterone will help keep the pregnancy going until the placenta takes control, which is usually about 10 weeks gestation. Relaxin is produced by the corpus luteum at the same time as it is released by the placenta.  If pregnancy does not happen, relaxin and progesterone levels will progressively decrease. Your body will prepare to remove the uterine lining during your next period since these hormones are no longer maintaining it.