Hair loss options
First, it's great that you've seen a doctor and ruled out the other possible causes of hair loss. Many women experience excess shedding after pregnancy due to the hormonal changes. Dr. McAndrews advises that this usually resolved on it's own and the hair returns to normal within a year after giving birth. Dr. McAndrews sees a lot of women who's hereditary hair loss worsens after childbirth. Prenatal vitamins will not affect the hereditary hair loss you are experiencing. Hair is not alive, but is made of keratin and is essentially a string. Following a healthy diet, including vitamins, helps to build a better string, but it will not stop the hereditary influences from causing the hairs to miniaturize.
Rogaine is the the only FDA approved therapy for women. Dr. McAndrews advises his female patients to use the 5% foam. One tip to know, when you start using Rogaine, it will cause more shedding that usual, but this is temporary and will resolve in a week or so. It can also be irritating, so we recommend that patients acclimate to the product. Start by applying it every 2 or 3 nights and gradually work up to every night. When nightly applications are going fine, gradually start applying every 2 -3 mornings and work up to every morning. It may take several weeks, but you will usually experience less shedding and irritation.
You can also consider hair transplants, but try the Rogaine first and see how it goes. We usually advise patients to give is 6-12 months for full effectiveness. It may not regrow hair, but it will help you keep what you have.
Hope that helps!