Hormones during pregnancy part 1

Amanda Gwynne shares an insight into hormones during pregnancy. Part 1 looks at Human Chorionic Gonadotrophin (HCG) and Progesterone.

pregnancy hormones

Pregnancy is one of the most amazing events of a woman’s life and brings with it many changes, both physical and emotional. The majority of these changes occur because of the finely tuned release of hormones essential to sustaining a new life developing and growing within our uterus.

Hormones are secreted by our endocrine system, derived from the Greek ‘endo’ meaning inside and ‘crinis’ which is secrete. Their job is to trigger and regulate activity throughout our bodies. Our whole sexual health and fertility, the creation and continuation of our pregnancy depend on our hormones. Over the next few weeks, I am going to discuss the various hormones and their effects during pregnancy and birth. This week we look at HCG and Progesterone.

The pregnancy hormones Oestrogens, Human Chorionic Somatomammotrophin (HCS) and Melanocyte Stimulating Hormone is covered are part 2.

Human Chorionic Gonadotrophin (HCG)

  • Produced by the chorionic villi after implantation of an embryo
  • Stimulates an increase in production of oestrogen and progesterone in the Corpus Luteum to prevent menstruation
  • Maintains high levels of hormones to maintain early pregnancy until the placenta is mature enough to take over
  • Levels peak at about 70 days
  • The main hormone measured in pregnancy tests
  • HCG may be responsible for early pregnancy symptoms such as morning sickness and fatigue


  • Major hormone of pregnancy
  • Produced initially by the Corpus Luteum of the ovary
  • Appears to decrease maternal immune response in early pregnancy facilitating acceptance of the embryo by the body
  • Progesterone is produced by the placenta from approximately 12 weeks of pregnancy with a steady rise in levels until labour and birth
  • It decreases contractility of uterine smooth muscles preventing contractions during pregnancy
  • Levels of progesterone drop at the end of pregnancy which may be a ‘trigger’ for the onset of labour
  • Relaxes smooth muscles and may cause heartburn and constipation
  • Hair may look thicker and glossier, as progesterone stimulates the hair follicles to go into a resting phase
  • Softens cartilage which may result in pelvic girdle discomfort
  • Inhibits prolactin during pregnancy, but may help trigger milk production due to rapid falls in progesterone levels after birth

Understanding the function of your fluctuating hormones during pregnancy may make it easier to live with some of the minor disorders and discomfort that you may experience. The knowledge that the effects of pregnancy hormones won’t last forever is a comfort too!

Photography: Sean McGrath @Flickr

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