Estrogen and Progesterone
Although doctors have conflicting ideas on which hormones cause what, it seems certain that the two hormones that play a major role in pregnancy are estrogen and progesterone. These hormones are responsible for the bulk of pregnancy symptoms experienced by expectant women.
- Breast soreness and sensitivity, for example, are caused by increasing levels of these hormones and should diminish significantly after the first trimester.
- Another area of sensitivity is your sense of smell, also thought to be a side effect of rapidly increasing hormones. It's not uncommon to be overwhelmed by certain smells that you liked before, or to find that certain foods are now repulsive to you.
- Fatigue is a side effect of progesterone, which has the same effect on the brain as some sleeping tablets! This is why drowsiness, and even complete exhaustion at times, occurs. But energy levels generally return once you enter the second trimester.
- One function of progesterone is to inhibit the smooth muscle in the uterus from contracting, thus allowing the fetus to grow with the expanding uterus. However, the hormone is not selective. As progesterone levels increase, other smooth muscles in the body may be affected, such as the lower esophageal sphincter whose shifted gear functioning may result in increased heartburn and acid reflux, especially in the later stages of pregnancy.
- The bowel muscles also relax, and since the bowel contains gas, the muscle tone decrease causes bowel distention. A bloated feeling is thus very common in pregnancy.
- Progesterone also softens cartilage, so it may be responsible for the hip and pubic bone pain that often accompany pregnancy.
Hormones and Emotional Fluctuations
While these physical symptoms are obvious, there are other effects of pregnancy hormones, which are just as important to recognize. St. Louis psychologist Dr. Diane Sanford, PhD, says that significant changes in your hormones can affect your levels of neurotransmitters, the brain chemicals that regulate mood.
You're most likely to experience these changes at around six to 10 weeks, and then again in the third trimester as your body prepares for labor and delivery. All women respond differently, so you can expect to feel anything from mood swings to depression or states of anxiety.