Estrogen hormones are most associated with women, although men produce estrogen also. Still, the most vital role estrogen hormones play is during a pregnancy. These hormones are extremely important for the proper development of a fetus. In fact, low estrogen levels can play a factor in infertility and miscarriages, according to the University of Maryland Medical Center.

Definition

There are three important estrogen hormones: estradiol, estriol and estrone. All three hormones are vital to the development of a woman’s breasts and ovaries and for egg production. Estriol, however, is the one that is most important in pregnancy.

Function

Estriol is produced by the ovaries and the placenta during pregnancy. Estriol levels can be measured as early as the ninth week of pregnancy, according to the University of Michigan Health System. Estriol levels increase throughout the pregnancy and help the uterus grow, increase blood circulation in your body and the placenta and trigger organ development in the fetus. Estrogen hormones also guide bone development in your baby. Along with helping your baby develop, estrogen also regulates progesterone, another vital hormone in a healthy pregnancy. Progesterone keeps the placenta functioning correctly, among other things.

Significance

Very low levels of estrogen hormones can cause miscarriages, according to Science Daily. In pregnancies that progress, lower levels of estrogen can hinder fetal development, especially in female babies, which can be born with low levels of eggs in their ovaries.

Considerations

Estrogen is also vital for milk production in the breasts, according to What to Expect. In some women, estrogen levels drop dramatically after birth, leading to difficulties with breastfeeding.

Expert Insight

Low estrogen levels can inhibit conception in a number of ways. First, ovulation is triggered in part by estrogen, so ovulation may not even occur if estrogen levels are too low. Second, the uterine lining, which thickens in readiness for a fertilized egg, may remain too thin for the egg to implant and survive if estrogen levels are too low. For that reason, many women who are trying to get pregnant can take fertility drugs containing estrogen (and usually progesterone) to aid in ovulation.