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Stages of Pregnancy: First, Second, Third Trimester

stages of pregnancy

Pregnancy occurs when a sperm cell from a male fertilizes an egg cell from a female. It officially starts when an egg implants in the lining of the uterus.

During pregnancy, the body of a woman undergoes significant changes to provide the environment for a fertilized egg (zygote) to develop into a fully formed fetus and eventually give birth to a child.


When a woman misses one or more periods, she usually knows she is pregnant. Women often experience premenstrual symptoms before they miss their periods, so women who miss their periods are not always pregnant. This process of pregnancy includes several steps you need to know:

  1. Ovulation: Ovaries release mature eggs The release of a mature egg by a woman’s ovaries, generally in the middle of her menstrual cycle. It travels into the fallopian tube.
  2. Fertilization: To achieve pregnancy, sexual contact is required during ovulation. Sperm is ejaculated from the male’s penis into the female’s vagina during intercourse. They then swim through the cervix and into the uterus, eventually arriving at the fallopian tube, where the egg is located.
  3. Fusion of Egg and Sperm: If a sperm successfully reaches and penetrates the egg in the fallopian tube, fertilization occurs. This event results in the formation of a zygote, which contains genetic material from both the male (sperm) and female (egg) contributors.
  4. Zygote development: The zygote divides after fertilization and develops into an embryo. The embryo then travels down the fallopian tube and into the uterus.
  5. Implantation: Embryo attaches itself to the lining of the uterus.This marks true pregnancy.
  6. Embryonic and Fetal Development: Over the course of pregnancy, the embryo develops into a fetus. During this time, the fetus undergoes rapid growth and development, with the formation of major organs and body systems.

Every couple couldn’t conceive easily due to many factors such as infertility.They need proper medical intervention alongside fertility treatments.

Stages of pregnancy:

Stages of pregnancy ist trimester of pregancy

Pregnancy normally lasts for 40 weeks. It typically starts from the first day of your last period.

There are three stages of pregnancy also known as trimesters.

  • First trimester           (1 to 12 weeks)
  • Second trimester      (13 to 27 weeks)
  • Third trimester          ( 27 to 40 weeks) 

First Trimester:

The first trimester of pregnancy spans from Week 1 to Week 12. It is the most critical phase of pregnancy in which several changes are happening to the mother and developing fetus. Here’s a detailed overview of the first trimester of pregnancy:

Week 1-2: Conception and Early Development

  • Conception: Pregnancy begins with the fertilization of an egg by a sperm cell during sexual intercourse. This forms a zygote containing the genetic material of both parents.
  • Implantation: The zygote travels down the fallopian tube and attaches itself to the uterine lining, officially marking the start of pregnancy.

Week 3-4: Embryonic Development Begins

  • Embryo Formation: At this stage, the zygote starts dividing and transforms into an embryo. Notably, the neural tube begins to take shape, eventually becoming the foundation for the brain and spinal cord.
  • Hormonal Changes: The body initiates the production of human chorionic gonadotropin (hCG), a hormone detectable in pregnancy tests. Increasing levels of hCG trigger a range of common pregnancy symptoms, including fatigue, frequent urination, breast tenderness, and morning sickness (which may include nausea and vomiting).
  • Common Symptoms: Women often experience fatigue, frequent urination, breast tenderness, and morning sickness (nausea and sometimes vomiting).

Week 5-8: Rapid Development

  • Organ Formation: During these weeks, the embryo experiences significant growth, leading to the formation of major organs and essential structures. Notably, the baby’s heart begins to beat, and limb buds become apparent.
  • Morning Sickness: This period may see the peak of morning sickness, including nausea and potential vomiting. Coping strategies such as eating small, frequent meals and staying well-hydrated can be effective in managing these symptoms.
  • Prenatal Care: Scheduling your initial prenatal care appointment with a healthcare provider is essential during this phase. It allows for the monitoring of the pregnancy’s progress and offers valuable guidance for a healthy pregnancy journey.

Week 9-12: Transition to the Second Trimester

  • Fetal Development: The embryo is now considered a fetus. It has distinct facial features, fingers, and toes. Most of the critical organ development is completed.
  • Gender Formation: In some cases, the gender of the baby may be determined through ultrasound at the end of this trimester.
  • Weight Gain: Gradual weight gain begins during the first trimester. Healthcare providers will advise on appropriate weight gain based on individual circumstances.
  • Exercise: Do some workout at home it will keep you physically fit and active.Discuss with your healthcare provider for proper guidance.
  • Rest and Self-Care: Adequate rest and self-care are essential during this period. Pregnancy can be emotionally and physically demanding, so listen to your body and seek support when needed.
  • Screening Tests: Depending on your healthcare provider’s recommendations, you may undergo certain screening tests or genetic counseling during the first trimester to assess the risk of genetic disorders.

Second Trimester:

Second trimester starts from 13 to 27 weeks. Morning sickness is way less than the first trimester . This is the best part of pregnancy but several mood fluctuations occur during this phase because she is suffering from many physical changes during this tenure.

Fetal development :

  • Fetal movement: Fetus starts to move during the second trimester and you can feel their movement which is an exciting phase for all the mothers.
  • Organ development: Mostly all the organs developed  in this trimester.
  • Gender determination: Many doctors can determine gender around 20 weeks by performing some tests in the second trimester.
  • Your baby can hear your voice at the end of the second trimester and starts to recognize you. If a baby born at the end of this trimester is known as premature birth, he will be fine because its development is complete.
  • Vernix formation: Tiny hairs and protective substance known as vernix starts to appear on the fetus body in this trimester.

Physical changes in mother:

  • Feeling good: This is the best part of the whole pregnancy. You feel comfort in this period.
  • Stretch marks:Skin over belly and breast may stretch causing  stretch marks. These marks may fade away over time.
  • Weight gain: You start to gain weight during the second trimester.
  • Baby bump: It starts to get prominent due to fetus growth, and you need maternity clothes.
  • Emotional changes 

Third Trimester:

The third trimester is the last period of pregnancy, including major development and growth. It starts at 28 to 40 weeks, or until delivery.

Fetal development:

  • The fetus starts to gain weight, and its organs are completely developed. Size also increases, which causes decreased movement in the womb. If you notice decreased movements, consult with your doctor as soon as possible.
  • Lung development is completed in this trimester, and they support the fetus to breathe outside the womb now.
  • Breech position: your baby might be

 Physical changes in mother:

  • Baby bumps become more prominent, and it causes low back pain.
  • Posture changes.
  • Fetuses impose pressure on your diaphragm, which is why some women experience difficulty breathing in this trimester.
  • Continued pressure on the pelvic region causes pelvic girdle pain and pubic dysfunction.
  • Frequent urination 
  • Heartburn 
  • Swelling on the ankle, foot, and hands also occurs, known as edema.

Psychological changes:

  • Mixed feelings of  joy and stress at the same time for meeting new born. Its time to pack for hospital bag.
  • You may be worried about labor and birth either its normal or  c-section.

Tips for healthy pregnancy:

  • Stay hydrated
  • Manage stress
  • Exercise 
  • Ask help
  • Seek support
  • Connected to other mom to be 
  • Educate yourself
  • Listen to your body
  • Safe medication

Read Also: What is a Baby Planner?

Rose Smith
Rose Smith Writer, Pregnancy guide specialist Expertise Rose Smith is a dedicated and experienced writer, specializing in the field of Nursing and pregnancy guidelines. With a strong educational foundation, extensive experience, and a passion for supporting expectant parents, Rose has become a go-to source for reliable pregnancy advice and information. Experience Rose Smith's professional journey is marked by a wealth of experience: Authorship: Rose has authored numerous articles, essays, and books on pregnancy guidelines, all backed by her academic knowledge and practical insights. Pregnancy Workshops: She has conducted workshops and seminars, both online and in-person, providing expectant parents with practical tools and advice. Consulting: Rose has worked as a pregnancy consultant, offering personalized guidance to expectant mothers and couples. Media Contributions: Her expertise has been featured in various publications, including parenting magazines and health websites. Education Rose Smith holds a Master's degree in Nursing from Oxford University, where she laid the foundation for her expertise in maternal health, prenatal care, and pregnancy-related topics. Additional Certifications Certified Nurse-Midwife (CNM) Doula Certification: Doulas, who provide emotional and physical support during pregnancy and childbirth, often seek certification through organizations like DONA International. Childbirth Educator Certification. University Specialties As a proud alumna of Oxford University, Rose's areas of specialization include: Maternal Health: Her academic background has equipped her with a deep understanding of the physical and emotional aspects of pregnancy and maternal well-being. Prenatal Care: Rose's education focused on the importance of proper prenatal care and its impact on a healthy pregnancy. Nutrition and Pregnancy: She has in-depth knowledge of nutrition during pregnancy and its role in fetal development.

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