Estrogen and Progesterone

Women and our hormones:

The 2 BIG pregnancy hormones play a vital role during the first trimester and second trimester of pregnancy, including triggering fetal development and common pregnancy symptoms.

The Role Estrogen Plays in Pregnancy 
  
Making things grow: No pregnancy proceeds without guidance from the big kahuna of hormones: estrogen. Busy estrogen, produced by the ovaries and later by the placenta, helps the uterus grow, maintains the uterine lining (where your budding baby is safely nestled), steps up blood circulation, and activates and regulates the production of other key hormones. In early pregnancy, estrogen promotes the growth of your impressively bountiful — and tender — breasts; later on, it helps develop their milk-making machinery. Baby benefits too: Estrogen triggers the development of those little organs and regulates bone density in those developing arms and legs. Whew! 
  
Increasing blood flow: The nose knows all about estrogen, too; the hormone increases blood flow to mucous membranes and causes them to swell and soften, giving mom-to-be an endlessly stuffy nose, plus sinus congestion, headaches, and postnasal drip. Your flushed pregnant "glow" — although sometimes you're more likely to see red rashes and blotches (which you'll strive to wear with pride, right?) — stems from the same extra blood flow to your skin, as does the annoying itchiness in your now ruddy palms. 
  
Causing skin to be more sensitive: Prefer cool hues to warm reds? Estrogen is here to help, creating the spidery blue network of veins on your chest (the extra vessels nourish your burgeoning breasts) and the mottled blue skin you might get when you're cold. For yet more color change, estrogen, along with progesterone and melanocyte-stimulating hormone,can cause skin discolorations (hyperpigmentation), like the darkening of the nipples, areola, and white line that runs down your abdomen. The skin on your forehead, nose, and cheeks may start to look particularly tanned, creating the chloasma, or "mask of pregnancy." It's a sign that your skin may be more sensitive than usual to sunlight, so take extra care. 
 
The Role Progesterone Plays in Pregnancy
  
Keeping things working properly: The other big mama of maternal hormones is progesterone (a "pro-gestational" hormone, hence the name), manufactured first by the ovaries and then by the placenta starting around the second trimester. Progesterone keeps the placenta functioning properly and the uterine lining healthy and thick, and it stimulates the growth of breast tissue. It also cracks down on pre-pregnancy's natural contractions of the smooth muscle of the uterus, allowing your baby to grow in your expanding (and expanding, and expanding…) womb. 
  
Causing discomfort: Creating room in the uterus is for your baby's benefit, of course — but by taking the squeeze off smooth muscle elsewhere, progesterone, with the help of the hormone relaxin, prompts all manner of GI discomforts: indigestion, heartburn, and constipation, just to name a few. Lax muscles in the lower intestine, for example, allow gases to distend the bowel, bringing about an even more bloated belly, as if that were possible. 
  
Softening cartilage:  Again with relaxin, progesterone helps to soften cartilage, loosening joints and ligaments, contributing to late-pregnancy aches in the hips and pubic bone. Even your teeth and gums take a beating; gums swell and bleed under the influence of progesterone, which also bathes bad mouth bacteria in a nourishing brew, contributing to "pregnancy gingivitis." Breaking out with acne for the first time in years and slippery with sweat at the slightest exertion? Progesterone is at play again, increasing secretions from the sweat glands.