Uva Ursi
Vitex
Vervain (Verbena officinalis): Vervain is reputed to act as an abortifacient and oxytocic agent with documented in-vivo uteroactivity and should not be taken during pregnancy. Vervain has reported galactogogue properties and has been traditionally used to stimulate milk supply.
Wakame
Watercress
White Willow Bark: I'm afraid there just isn't enough clinical data about how white willow might affect a developing infant, so it's use is not recommend (and is not traditionally used) during pregnancy. The main active ingredients, salicin and salicortin, are similar to aspirin and although salicin does not thin the blood like aspirin does, it can cause Reye syndrome in children (orally). You can think of it as using a product containing aspirin, and decide from there. White willow bark may also be found in some skin care because salicin has antiseptic and anti-inflammatory properties and is used as an astringent.
Wild Cherry Bark
Wormwood
Yarrow
Yellow Dock Root