The reason women of childbearing age most often seek natural estrogen replacement is to treat a condition called endometriosis. And the purpose of estrogen replacement in women seeking to conceive, unlike women who have passed menopause, is to get estrogen levels down, not to make them higher.
The herbal treatment that does the most women the most good in treating endometriosis is a plant from Traditional Chinese Medicine known as dong quai. Also known by its Japanese name tang-kuei and by its botanical name Angelica sinensis, this herb was originally prescribed to treat conditions the ancient Asian masters of herbal medicine termed "stasis". This was exactly what it sounds like. Stasis of the blood in the womb resulted in "static" fertility, and only reinvigorating the womb would empower fertility. OB-GYN's in modern China and Japan probably would tell you that they regard the historical descriptions of dong quai as quaint. The fact is, however, that multiple clinical trials involving women volunteers have confirmed that this herb stops excessive estrogen production in the ovaries. Too much estrogen during the first half of a woman's period causes "rough" growth of the endometrial lining of the uterus, making it difficult for a fertilized egg to implant itself to begin pregnancy.
In women who have endometriosis, lowering estrogen levels during the first half of the menstrual cycle stops the unusual swelling of tissues in the lining of the uterus, and sometimes blocking the fallopian tubes, preventing the release of the egg at ovulation. And since dong quai also stops excessive testosterone production, it can reverse the acne, aggression, and unusual hair growth that sometimes accompanies PCOS (polycystic ovarian syndrome). Many women also benefit from small amounts of soy foods in their diets. If you frequent Japanese or Korean restaurants, you may be served a side dish of fried or baked tofu, just a couple of bites of this soy food with a flavorful sauce. There are reasons the servings are so small. A woman's body can only process the estrogen-like soy isoflavones in about 1/2 ounce, or about 15 grams, of soy food per day. Any more soy, and the isoflavones just break down in the colon without ever being absorbed. Women who take red clover or soy isoflavones do not need to eat any soy foods at all, and won't benefit from them if they do.