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Conception
• Growth of the Egg
• Development of Sperm
• Fertilization
• Implantation
Everyone knows that the sperm and egg need to meet for conception to occur, but the process is more complicated than many realize. The sperm and egg need to first grow to maturity and then unite at the right time. To maximize your chances for conception, learn more about the process below.
Growth of the Egg
During the course of the month, the woman’s eggs grow to maturity in follicles, or fluid-filled sacs, in each of her two ovaries. When one egg has fully matured, it bursts through the follicle and travels down the fallopian tube. This process is called ovulation, and occurs about two weeks after the woman’s last menstrual period. Ovulation is a woman’s most fertile time of the month.
Following ovulation, the follicle formerly containing the egg transforms into the corpus luteum. The corpus luteum generates progesterone in the event of a pregnancy. The progesterone thickens the lining of the uterus for the fertilized egg.
The egg remains in the fallopian tube for up to 24 hours. The process whereby the sperm and egg come together is called fertilization. If not fertilized, the egg travels down the fallopian tube to the uterus. During menstruation, the egg and lining of the uterus are shed.
Development of Sperm
Sperm are produced in the ducts of a man’s testes and the endocrine system controls this process. Sperm maturation occurs in five cycles of approximately two weeks each, so it takes 70+ days, or more than two months, for complete sperm development.
While infections like the flu impact sperm, the effect is usually temporary, because the sperm production process lasts for 70 days. However, sexually transmitted diseases can affect sperm health permanently by decreasing sperm motility. Similarly, contracting the mumps after puberty can cause inflammation of the testes, lessening sperm production.
In these cases, treatment from a doctor is crucial, and men are usually treated with antibiotics or surgery.
In addition, environmental factors such as toxic pollutants, prescription drugs, zinc deficiencies, alcohol and drug abuse, anabolic steroid use, and heat can impact sperm development.
Fertilization
If the timing is right, an egg and sperm will both be in the fallopian tube at the same time. The sperm can live up to five days in the fallopian tubes, waiting for the egg to arrive.
Fertilization occurs when a sperm penetrates the egg in the fallopian tube. Many sperm struggle to fertilize the egg, but only a single sperm penetrates. Once it does, the fertilized egg creates a barrier that precludes other sperm from entering.
The fertilized egg gets half of its genetic material from its mother, and half from its father. The sperm determines the gender of the baby. The mother can only supply X chromosomes, but the sperm can supply either X or Y. If an X sperm fertilizes the egg, the baby will be a girl; if a Y sperm does, the baby will be a boy.
Implantation
The fertilized egg, or zygote, begins travelling down the fallopian tube, where it starts dividing into many cells. Some of these cells form the embryo, or growing baby. Other cells become the placenta, an organ that filters food and oxygen from the mother’s blood to the baby. The placenta also begins to produce progesterone, instead of the corpus luteum.
An exchange of hormones between the embryo and the uterine wall helps it attach to the wall. The uterine wall grows and thickens to support the developing baby. The placenta produces hCG (Human Chorionic Gonadotropin) to keep the pregnancy viable and help the fetus develop. Over-the-counter pregnancy tests measure the level of hcG in urine to determine pregnancy. The hCG also maintains the uterine lining.
After the eighth week of pregnancy, the developing baby is called a fetus. At this point, all of the baby’s vital organs have already formed.
