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Better Understanding Conception
Most doctors and midwives calculate the start of pregnancy from the first day of your last menstrual period. This is known as the "menstrual age" and is usually about two weeks ahead of when conception actually occurs. Click here or visit HBs Ovulation Calculator to find out when the right time is for you.
Here is an overview on conception:
Ovulation: Once a month, in one of a woman's two ovaries, a number of immature eggs begin to develop in small fluid-filled cysts called follicles. Typically, one of the follicles is selected to complete development (maturation). This "dominant follicle" inhibits the growth of all of the other follicles, which stop growing and perish. The mature follicle ruptures and releases the egg from the ovary (ovulation). Ovulation normally occurs about two weeks before a woman's next menstrual period begins. Click here or visit the belly tube to see exactly how this process takes place.
Development of Corpus Luteum: After ovulation, the ruptured follicle develops into a structure called the corpus luteum, which secretes two hormones, progesterone and estrogen. In this process, the progesterone helps to prepare the endometrium (lining of the uterus) for the embryo to implant by thickening it.
Release of Egg: The egg is released and travels into the fallopian tube where it waits for a single sperm to penetrate it during fertilization (the union of egg and sperm). The egg can be fertilized up to about 24 hours after ovulation. On average, ovulation and fertilization will occur about two weeks after your last menstrual period.
Menses: If there are no sperm to fertilize the egg, it and the corpus luteum will degenerate, halting the high level of hormones that have been released. This causes the endometrium to shed away, resulting in menstrual bleeding. Once this process has finished, the cycle will then repeat itself.
Fertilization: Once a sperm meets and penetrates a mature egg after ovulation, it will fertilize it. Once penetrated, changes occur in the protein coating around the egg to prevent other sperm from entering. At the moment of fertilization, your baby's genetic make-up is complete, including its sex. The woman has two X chromosomes therefore; she can only produce the X. Sperm however, can be either X or Y. If the sperm that fertilizes the egg is the X chromosome, your baby will be a girl (XX). If the Sperm is a Y chromosome, then you will be having a boy (XY). Click here to read more on how to increase your chances of having a boy or a girl.
Implantation: Within about 24-hours after fertilization, the egg will begin to divide rapidly into numerous cells. Typically, it will remain in the fallopian tube for about three days. As the fertilized egg (zygote) passes slowly through the fallopian tube, it continues to divide while on its path to the uterus. Next, the zygote will attach itself to the endometrium (a process called implantation). At first, the zygote will become a solid ball of cells and then turn into a hollow ball of cells called a blastocyst. Before implantation takes place, the blastocyst will break out of its protective covering. Once the blastocyst begins contact with the endometrium, an exchange of hormones will help with the attachment of the two. In some instances, women will notice slight bleeding (or spotting) for one or two days around the time of implantation. The cervix will be sealed by a plug of mucus and the endometrium becomes thicker.
Within about two to three weeks, the blastocyst cells will begin to grow into clumps of cells within the blastocysts wall, and the baby's first nerve cells have been formed. Your developing baby is called an embryo from the moment of conception to the eighth week of pregnancy. From week eight, until the moment of birth, your developing baby is known as the fetus.
Pregnancy Hormones: The hormone that is present in a mothers blood from the time of conception is known as Human Chorionic Gonadotrophin (HCG), and is produced by the cells that form the placenta. This is the hormone that is detected in a pregnancy test; however, it usually takes about 30 days from the first day of your last period for the HCG levels to be high enough to be detected by the majority of pregnancy tests.
Because of the distinct changes that take place during a pregnancy, there are three developmental stages that are known as trimesters, or three month periods.
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