The first trimester is the earliest phase of pregnancy. It spans from week 1 to the end of week 12. During this time, your baby grows faster than at any other time. By 6 weeks, a heartbeat can usually be detected and by the end of week 12, your baby's bones, muscles, and all of the organs will have formed.
This week marks the approximate day of your last menstrual cycle (LMP). It's important to understand that technically, you're not yet pregnant this week! Week 1 is calculated from the first day of your LMP, and this date is used to estimate your due date later on. Think of it as the starting point for tracking your pregnancy journey. While there's no baby yet, your body is preparing for the potential for pregnancy. Hormones are at work, and the lining of your uterus is getting ready to support a fertilized egg, should conception occur. This week is all about preparing the groundwork for the incredible journey ahead. The journey from conception to birth is a complex and miraculous one. The fertilized egg, if conception occurs, will travel down the fallopian tube and implant in the uterus.
Based on a 28-day cycle, this week is the approximate date of conception. Ovulation occurs, typically around day 14 of a 28-day cycle, but it can vary. Some women experience a twinge of abdominal pain or a feeling of pressure – known as mittelschmerz (literally "middle pain") – around the time of ovulation. This sensation is associated with the release of the egg from the ovary. The ovum (egg) is only viable for about 24 hours, so fertilization must occur within this window. This is why timing intercourse around ovulation is key for couples trying to conceive. Sperm can survive in the female reproductive tract for several days (up to 5), so having intercourse in the days leading up to ovulation can also increase the chances of fertilization. If fertilization occurs, the sperm will meet and penetrate the egg in the fallopian tube. The fertilized egg (zygote) then begins its journey down the fallopian tube toward the uterus. Once it reaches the uterus, the embryo will implant itself in the uterine wall. This implantation process is crucial. The embryo sends out tiny "roots" that will eventually connect with your blood supply, providing the nutrients and oxygen necessary for its growth and development. This connection will form the basis of the placenta, the organ that sustains the baby throughout pregnancy.
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.
The fertilized egg develops into a blastocyst and implants in the uterine wall. The placenta and embryo begin to develop.
The embryo's heart, brain, spinal cord, and other organs begin to form. Arm and leg buds appear, and the embryo grows to about 1/2 inch long.
The embryo's heart, brain, spinal cord, and other organs begin to form. Arm and leg buds appear, and the embryo grows to about 1/2 inch long.
The embryo's heart, brain, spinal cord, and other organs begin to form. Arm and leg buds appear, and the embryo grows to about 1/2 inch long.
The embryo's heart, brain, spinal cord, and other organs begin to form. Arm and leg buds appear, and the embryo grows to about 1/2 inch long.
The embryo is now called a fetus. All essential organs have formed and the fetus can move its limbs. External genitalia begin to develop.
The embryo is now called a fetus. All essential organs have formed and the fetus can move its limbs. External genitalia begin to develop.
The embryo is now called a fetus. All essential organs have formed and the fetus can move its limbs. External genitalia begin to develop.
The embryo is now called a fetus. All essential organs have formed and the fetus can move its limbs. External genitalia begin to develop.