Medically Reviewed By Experts Panel
Welcome to the first trimester of pregnancy!
Pregnancy is divided into three trimesters of approximately three months each. The first trimester begins on the first day of your last period and lasts until the end of week 12 or 13. The first trimester is a critical time for the development of the foetus (an unborn young still developing in its mother’s body), as all of the major organs and systems begin to form during this time. It is important to take care of your overall health by eating more conscientiously a wholesome diet and getting regular exercise.
It includes conception (or fertilization), when the sperm travels through the vagina and into the uterus to join an egg. In the initial days, or actually until a couple of weeks have passed since conception, you may not know for certain that you are pregnant.
So the first trimester actually starts before you become pregnant. Since you don’t always know when fertilization occurred, doctors calculate pregnancy based on the first day of your last menstrual period. A full-term pregnancy lasts around 9 months or roughly 40 weeks long.
- In week 1 your baby may not have been conceived as yet. Your expected birth date is counted from the first day of your last period. Actually, a pregnancy starts with fertilization when a woman’s egg joins the man’s sperm. This happens near the end of the second week.
- Your baby in the early development stage after fertilization to week eight is referred to as embryo, after which it is known as a foetus (an unborn young still developing in its mother’s body).
- During this trimester, your baby grows faster than any other time. The embryo (a baby in the early stages of development before birth) is only a few millimetres long at the beginning of the first trimester, but by the end of the trimester, it has grown to about three inches long and weighs around one ounce.
- In the first few weeks after conception, your hormone levels change significantly as the uterus begins to support the growth of the placenta and the foetus. Interestingly, the word placenta comes from the Latin word which means a type of cake. So the round-oval cake like organ forms during the embryonic stage. It provides oxygen and nutrients to the growing baby.
Besides the embryo growing inside you, you will also begin to feel changes in yourself. Increased level of hormones may cause mood swings, morning sickness, and enlargement of breasts or mammary glands. Feeling tired, tender breasts and nausea are all common symptoms.
