The early signs of pregnancy are caused by certain hormones in the mother's body that initiate the changes needed for the growth and development of the baby. These hormones are estrogen, progesterone and human chorionic gonadotropin (hCG), which is used as a marker for pregnancy tests. The signs of pregnancy vary from subtle to more obvious and occur at different stages of the pregnancy.
Missed Periods
A missed menstrual period is most commonly the first sign of pregnancy in women, as noted by the University of Maryland Medical Center. This occurs because elevated levels of the hormones hCG and progesterone prevent the shedding of the lining of the uterus (womb). This allows the embryo to implant in the womb for a successful pregnancy. Blood spotting during implantation can be mistaken for a menstrual cycle.
Breast Tenderness
As described by the Cleveland Clinic, another sign of pregnancy is breast enlargement, tenderness and pain. The nipples also start to darken and become erect and sensitive during the early days of pregnancy. The breasts feel heavy and swollen.
Morning Sickness
Some women experience nausea and vomiting as early as the first two weeks of conception. Morning sickness can occur at any time of the day, but is common in the morning in most pregnant women. Certain smells, such as cooked foods and cigarette smoke, may trigger symptoms. Rising levels of hCG in the blood and the hormone estrogen, which slows down stomach emptying, cause nausea and vomiting, according to MedicineNet.com.
Frequent Urination
As mentioned by the Cleveland Clinic, another early sign of pregnancy is frequent urination. This occurs initially as a side effect of the high levels of the hCG. Later in the pregnancy, the growing uterus exerts pressure on the urinary bladder, causing more frequent urination.
Fatigue and Tiredness
Fatigue and tiredness are among the earliest signs of pregnancy and are caused by rising levels of progesterone, as noted by Mayo Clinic. The same hormone is also responsible for raising basal body temperature, which leads to feeling sluggish and sleepy. Progesterone also decreases blood sugar levels and lowers blood pressure, leading to fatigue, weakness and tiredness.
Mood Swings
The rapid changes in hormones levels during the early period of pregnancy cause mood swings, as described in MedicineNet.com. Pregnant women may feel irritation, stress, sadness, joy or delight. These changes are frequent and rapid and tend to settle down as the pregnancy progresses.
Headaches
Headaches and dizziness occur early in pregnancy due to increased blood flow to the head and hormonal changes in blood volume and blood pressure, as mentioned by the Cleveland Clinic.
