What are the causes of the common pregnancy symptoms?
Morning sickness or just plain nausea is the most common and most widely experienced early pregnancy symptom. It is believed to be hormonal (many hormones are produced by the fetus and the placenta). The onset is within three to four weeks of conception and will usually subside and disappear around ten to twelve weeks of gestation. Sometimes it persists for up to fourteen or sixteen weeks and, in exceptional cases, it may continue throughout the pregnancy. Another unusual scenario is where the symptoms disappear as expected at about twelve weeks, only to come back towards the end of pregnancy. Smoking exacerbates morning sickness. The severe form of pregnancy-related nausea and vomiting is regarded as pathological and is discussed in a separate chapter. What about dizziness and bloatedness? Dizziness, normally, starts later on in pregnancy. The cause is partially hormonal; progesterone, which is abundant during pregnancy, causes blood pressure to fall, especially on rising from a lyin
