There are a LOT of great herbs for the childbearing years. Ones that are nutritive, ones that are calming and, like yarrow, ones that have a great place in the medicine cabinet.
Yarrow has an intoxicating smell when dried. It has beautiful dainty white flower clusters with 4 petals each and feathery alternate leaves. An easy identification and is abundant in the wild.
Yarrow is the herb for menstruation, birth, and accident-prone children. It can be used as a styptic powder or fresh poultice to slow and stop external bleeding - like a cut or nosebleed. It can be blended with nutritive herbs like nettles and red raspberry leaf for a moon-time tea, especially for someone experiencing menorrhagia (heavy menstruation), and also as an after birth tincture (along with cramp bark) to reduce postpartum "after pains" and reduce bleeding... even stopping a hemorrhage.
So, if you're looking for an all around useful herb - go outside and you're bound to find some yarrow. Dry it, and keep it in a cool dry place out of sunlight. If you're birthing at home start an infusion when you start labor and let it infuse while you labor for use after the birth if needed. It's medicinal value increases the longer it infuses. It will be bitter, but taken spoonfuls or 1/4 C at a time every 15 minutes (or in tincture form) it can be very useful.
What is your experience with yarrow?