Phases of Pregnancy
As mentioned prior, human pregnancy lasts around 36 weeks and is divided into 3 developmental trimesters as defined by the Cleveland Clinic:
First trimester: The amniotic sac and placenta develop and a primitive face and heart tube will develop. The circulatory and urinary systems are developed and the baby begins to develop rudimentary teeth. By the end of the first trimester, the baby is about 4 inches long and weighs about one ounce. Instances of miscarriage are high during the first trimester but drop considerably by the end of it.
Second trimester: The baby begins to develop facial features as well as its nervous system and genitalia. The baby is able to respond to stimuli such as light and sound and by the end of the second trimester, a baby is likely to survive if born early. The baby is about 14 inches long and weighs 2 to 4 pounds.
Third trimester: The baby continues to mature and develop reserves of body fat, the lungs are fully closed and the baby has more coordinated reflexes. The baby’s position within the uterus changes so it is more optimal for birth (head-down position). The baby is 7 pounds and is about 18-20 inches long.
Take a look at the video below for a quick visual of how a baby and its mother’s body changes during pregnancy!
Stress in Pregnancy
While genetics and changes in a mother’s body can impact the outcome of pregnancy, another factor, stress on a mother, can impact a baby’s future health and development. “Stress” doesn’t just indicate physical strain on the body, but a myriad of other factors such as trauma, domestic violence, poverty, and pollution, to name a few. If a mother is put under high levels of stress during her pregnancy, this increases her stress hormones which in turn impacts her baby’s stress hormone levels. The baby is then born with elevated levels of stress hormones which later in life can cause anxiety, depression, heart disease, and weight problems. It is important for a mother to minimize her stress levels during pregnancy to ensure the best health for her baby, but this often isn’t possible due to her environment.
To hear a TedTalk on the subject, listen to Zaneta Thayer talk about stress and environment during pregnancy: