Expert: Sally Wendkos Olds - 3/29/2005

Question
Does breast size increase when a woman becomes pregnant since there is a possibility she will be breast feeding?

Answer
Dear Lisa,

Yes, breast size does increase during pregnancy and remains larger during lactation. Here's an excerpt from my book (see below) on the topic:

Regards, Sally

Sally Wendkos Olds
Author, THE COMPLETE BOOK OF BREASTFEEDING: Eiger & Olds, 3rd edition 1999, published by Workman Publishing & Bantam Books, and available in most public libraries, bookstores & La Leche League chapters.
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CHANGES IN YOUR BREASTS DURING PREGNANCY
When you first go to have your pregnancy confirmed, your doctor will perform a pelvic examination and will closely examine your breasts to look for signs that you have indeed conceived. Some of these signs that appear by the fifth or sixth week of pregnancy include: a persistent fullness and tenderness of your breasts similar to premenstrual sensations, the sudden prominence of the glands of Montgomery (little bumps located on the areola), and the enlargement and darkening of both your nipples and your areolae.
  The complete duct system in your breasts develops only now, when you are pregnant, stimulated in large part by the hormones from your placenta. The duct system is completed sometime during the middle trimester of your pregnancy. Thus milk is available for your baby even if you should deliver prematurely.
  By the time your baby is born, glandular tissue has replaced much of the fatty tissue in your breasts. The development of this glandular tissue is responsible for the enlargement of the breasts during pregnancy and lactation. By the time of your baby's birth, your breasts will be larger by about a pound and a half each. They will remain at about this size during the early months of lactation and then will probably revert to their previous size -- once you revert to your prepregnancy weight.
  The placenta, that organ that transmits nourishment and oxygen from your system to your unborn baby's, also has another function. It serves as a chemical factory: in early pregnancy it takes over from your ovaries the job of producing large amounts of hormones.
  Somewhere around the fifth month of your pregnancy, the placenta begins to produce a new hormone, human placental lactogen. This hormone stimulates the development of the alveoli, the little sacs where the milk is made. Once these are formed, your breasts begin to produce "early milk," or colostrum, a sticky colorless or slightly yellowish liquid that may occasionally drip from your nipples during the latter part of your pregnancy. (More about this "liquid gold" later.)
  During pregnancy your body experiences rising levels of a hormone that's very important for lactation, prolactin. Your pituitary gland has been producing prolactin all your life, but when you are not pregnant or nursing, its release is usually blocked by a hormone known as prolactin-release inhibiting factor (PIF). During pregnancy prolactin levels are high, but its action is inhibited by the high levels of estrogen in your system.