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Hormonal Changes During Pregnancy

Hormones are chemically diverse substances (e.g. steroids; peptides), which are released into the bloodstream in response to some stimulus, and activate cells, depending on the hormone in question. The main hormones involved in pregnancy and their functions are listed below.

Human Chorionic Gonadotropin (hCG) stimulates the production of oestrogen and progesterone within the ovary. It is released very early in pregnancy and isn't present at any other time. This is the hormone which pregnancy tests look for. Production of this hormone diminishes once the placenta is mature enough to take over oestrogen and progesterone production.

Oestrogen This hormone causes the breast tenderness and enlargement which are typical of early pregnancy. It is produced throughout pregnancy, and helps to regulate levels of progesterone and prepare the womb for the baby and the breasts for feeding.

Progesterone Prevents the womb from spontaneously aborting the foetus by building up the lining so that it can support the placenta , and by preventing the natural movement and contractions of the womb. This is the hormone which is responsible for the loss of interest in sex during pregnancy.

Prolactin Prolactin is produced by the pituitary gland. It is responsible for the increase in cells which produce milk within the breasts. Progesterone and oestrogen actually prevent milk from being produced. Immediately after birth, the levels of these hormones drop dramatically, allowing prolactin to stimulate the initial production of milk. Suckling also controls milk production. Prolactin also helps prevent a nursing mother from falling pregnant, but cannot be relied on as the only form of contraception.

Relaxin This is found early in pregnancy and is responsible for helping limit the activity of the womb and soften the cervix in preparation for delivery.

Oxytocin Oxytocin seems to be involved in reproductive behaviour in both men and women, and apparently triggers "caring" behaviour. It is also the hormone which allows contractions of the womb during pregnancy and labour . Contractions felt during breast feeding are also due to oxytocin. Also used to induce labour .

Prostaglandins These are tissue hormones and seem to play a role in getting labour started. Synthetic prostaglandins are used to induce labour in a pregnancy which has gone past its 40th week

The information in this page is presented in summarised form and has been taken from the following source(s):
1., Women's Health Section :

Other HON resources 
   From MedHunt

Hormones & Pregnancy


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Contact Last modified: Jun 25 2002