Week 3: Baby at Week 3:

This week marks a crucial turning point – fertilization! When a sperm successfully penetrates the egg, the egg's outer layer changes, preventing other sperm from entering. The egg then splits, and the nuclei of the sperm and egg join together. This fusion of genetic material is fertilization, the moment a new life begins. Women often experience increased sexual arousal near ovulation due to hormonal shifts. Estrogen levels peak near ovulation, leading to a wet, slippery sensation due to the fertile cervical fluid produced. This fluid is similar to sexual lubrication. The fertilized egg (now called a zygote) begins its journey down the fallopian tube toward the uterus. This journey takes several days. As it travels, the zygote undergoes rapid cell division. The zygote is a rapidly dividing ball of cells surrounded by a protective layer called the zona pellucida. This zona pellucida holds the cells together. The inner group of these cells forms a solid ball called the blastocyst, which will eventually become the embryo. The outer layer of cells, the trophoblast, will eventually form the placenta. The zygote receives nourishment from uterine "milk" (secretions from uterine glands) during this time before implantation. The sex of your baby is determined at the moment of fertilization by the sperm cell that fertilizes the egg. The embryo moves into the uterus about 80 hours after ovulation and begins to implant in the uterine wall about 72 hours after that. Implantation is a critical step; if it doesn't occur, the pregnancy won't progress. Around this time, the embryo folds over itself, beginning to form the neural tube, which will become the foundation of the baby's brain and nervous system. Until day 15, the developing life is considered a zygote. Sperm usually meet the egg in the outer third of the fallopian tube.