As with progesterone, estrogen is produced by the placenta throughout a pregnancy and the levels increase steadily until birth.

Each hormone plays a vital and complex role during a pregnancy and many of them interact with each other to stimulate various parts of the process.

One role of estrogen during pregnancy is to regulate the production of progesterone over the full term.  As estrogen is produced by the placenta, progesterone production is stimulated and regulated.

Apart from this, estrogen plays a very important role in the development of the foetus.  Without estrogen, the lungs, kidneys, liver, adrenal glands and other organs would never be triggered into maturation.  In fact, the placenta itself would never grow and operate properly if not for estrogen.

The following list shows some other known jobs undertaken by estrogen:

• Triggers the maturation of reproductive organs

• Help in the development of sexual characteristics

• Assists in the lactation process

• Regulates bone density in a foetus

• Maintains the endometrium during pregnancy

• Promotes blood flow within the uterus

• Maintains, regulates and triggers the production of other hormones

• Protects female foetuses from the effects of androgens in the mother's system. (Androgens are substances that have a masculinising effect).

The main external effect on women of the increased levels of estrogen during a pregnancy is the appearance of rashes or red blotches on the skin.  It is this effect that is often described as the 'glow' of pregnancy.

Introduction

1. Progesterone production

2. The role of progesterone

3. The role of estrogen (oestrogen)

4. Summary of some other hormones