Pregnancy Support Group

First trimester

Before pregnancy begins, a female oocyte (egg) must be fertilized, by male sperm in a process referred to in medicine as "fertilization", or commonly as "conception". In most cases, this occurs through the act of sexual intercourse, in which a man ejaculates inside of a woman, thus releasing his sperm inside of her. Though pregnancy technically begins at implantation, it is often convenient to date from the first day of a woman's last menstrual period. This is used to calculate the Estimated Date of Delivery (EDD).

Traditionally (according to Naegele's Rule, which is used to calculate the estimated date of delivery (EDD)), a human pregnancy is considered to last approximately 40 weeks (280 days) from the last menstrual period (LMP), or 37 weeks (259 days) from the date of conception. However, a pregnancy is considered to have reached term between 37 and 43 weeks. Babies born before the 37 week mark are considered premature, while babies born after the 43 week mark are considered postmature. However, the average length of pregnancy depends on various factors. For example, the first pregnancy tends to last longer than subsequent pregnancies.

An accurate date of conception is important, because it is used in calculating the results of various prenatal tests (for example, in the triple screen test). A decision may be made to induce labour if a baby is perceived to be overdue. Due dates are only a rough estimate, and the process of accurately dating a pregnancy is complicated by the fact that not all women have 28 day menstrual cycles, or ovulate on the 14th day following their last menstrual period. Approximately 3.6% of all women deliver on the due date predicted by LMP, and 4.7% give birth on the day predicted by ultrasound.

In medicine, pregnancy is defined as beginning when the developing embryo becomes implanted into the endometrial lining of a woman's uterus. In some cases where complications may have arisen, the fertilized egg might implant itself in the fallopian tubes or the cervix, causing an ectopic pregnancy. Most pregnant women do not have any specific signs or symptoms of implantation, although it is not uncommon to experience light bleeding at implantation. The outer layers of the embryo grow and form a placenta, for the purpose of receiving essential nutrients through the uterus wall. The umbilical cord in a newborn child consists of the remnants of the connection to the placenta. The developing embyro undergoes tremendous growth and changes during the process of embryonic and fetal development. Morning sickness aflicts about seventy percent of all pregnant women, typically only in the first trimester.

Second trimester

Months 4 through 6 of the pregnancy are called the second trimester. Most women feel more energised in this period, and begin to seriously put on weight. The first movement of the fetus, often referred to as "quickening", can be felt, as it begins to form into a recognisable shape. This typically happens by the fourth month. The reproductive organs can be recognized, and can distingush the fetus as male or female.

Third trimester

Final weight gain takes place, and the fetus begins to move regularly. The mother's belly button may "pop" out due to her growing belly. This can be uncomfortable, causing symptoms like weak bladder control and back-ache.