Even before pregnancy is confirmed, significant changes occur in the body. After fertilisation, the embryo journeys to the uterus and implants, causing hormonal changes that promote early development. Some women begin to feel more tired than usual, experience nausea, or notice breast tenderness, while others see no difference. As hormone levels continue to rise by week five, these changes may become more noticeable. Understanding this early phase can help you recognise symptoms and make informed decisions. This guide will take you through weeks one through five, covering key events, common signs, and top tips.
Weeks 1 & 2
Pregnancy is usually counted from the first day of the last menstrual period (LMP), even if conception has not yet occurred. During the 1st and 2nd weeks, the body prepares for ovulation by releasing hormones that promote pregnancy.
Key Developments This Week
Menstruation and Hormonal Shifts (Week 1)
The cycle begins with menstruation, during which the uterine lining left over from the previous cycle is shed. Hormonal levels, especially estrogen and progesterone, are low at this stage but begin to increase gradually. The brain signals the ovaries to start developing follicles containing an immature egg in preparation for ovulation.
Ovulation and Egg Maturation (Week 2)
One follicle becomes dominant and matures, eventually releasing an egg about day 14 of a 28-day cycle. The egg then travels unhappy the fallopian tube, which remains viable for about 12 to 24 hours, awaiting fertilisation. Cervical mucus becomes more transparent and more elastic, making it easier for sperm to move, while the lining of the uterus congeals in preparation for a possible pregnancy.
Symptoms and Signs
At this stage, there are usually no noticeable pregnancy symptoms because implantation has not yet occurred. However, ovulation signs may be evident, including:
- Increased cervical mucus – Ovulation causes a clear, stretchy discharge, which helps sperm travel.
- Mild pelvic discomfort – Some experience ovulation pain on one side of the lower abdomen.
- Higher basal body temperature – A slight rise in temperature after ovulation can indicate the fertile window.
Week 3
The third week marks the beginning of pregnancy as fertilisation occurs. If the egg and sperm unite, new life begins at the cellular level. This is the crucial stage in which the genetic material is determined, and early development begins before implantation.
Key Developments This Week
Fertilisation: The Union of Egg and Sperm
After ovulation, the egg has a short window of time, about 12 to 24 hours, to be fertilised. If a sperm is in the fallopian tube at the right time, it will successfully penetrate the egg, combining genetic material from both parents. This single-cell structure, a zygote, contains all the DNA needed to determine the baby’s sex, eye colour, and other hereditary traits.
Cell Division and Blastocyst Formation
Shortly afterwards, fertilisation, the zygote begins to divide rapidly as it moves down the fallopian tube. Within a few days, it transforms into a group of cells known as a blastocyst. This tiny structure has an outer layer that will eventually become the placenta, though the inner cells will form the embryo. The journey to the uterus continues over the next few days as the blastocyst prepares for implantation.
Preparation for Implantation
At the end of the week, the blastocyst reaches the uterus, but does not attach immediately. Instead, it floats for a while, allowing the uterine lining to achieve an optimal state for implantation, which occurs the following week. This is critical, as pregnancy is not officially established until the blastocyst has successfully implanted into the uterine wall.
Signs and Symptoms
At this stage, most women do not experience noticeable pregnancy symptoms because implantation has not yet occurred. However, some early signs may include:
- Mild cramping – A slight pulling sensation as the fertilised egg moves through the fallopian tube.
- Increased basal body temperature – If tracking body temperature, a continued rise may indicate pregnancy.
Since pregnancy hormones (hCG) are not yet at detectable levels, a pregnancy test will not show a positive result at this stage.
Week 4
In week 4, the fertilised egg completes its journey and implants into the uterine lining, officially marking the start of pregnancy. This critical step triggers the release of pregnancy hormones, which help maintain the uterine environment and promote early development.
Key Developments This Week
Implantation and Hormonal Changes
In week 4, the fertilised egg completes its journey and implants in the endometrium. This process triggers the release of human chorionic gonadotropin (hCG), a hormone that promotes early pregnancy and is detected in pregnancy tests. HCG helps maintain the endometrium and signals the body to continue producing progesterone, which is necessary to keep the pregnancy.
Embryo and Placenta Formation
When implantation occurs, the inner cells of the blastocyst begin to develop and become an embryo, while the outer layer begins to form the placenta. The placenta will then take over hormone production and provide the baby with oxygen and nutrients. Small blood vessels also develop at this stage, establishing a connection between the embryo and the mother’s blood supply.
Signs and Symptoms
Some women may begin to notice early pregnancy symptoms due to rising hormone levels. These can include:
- Implantation bleeding – Light spotting as the embryo attaches to the uterine wall.
- Mild cramping – A pulling or stretching sensation in the lower abdomen.
- Fatigue – Increased progesterone levels may cause tiredness.
- Breast tenderness – Hormonal changes can make breasts feel sore or sensitive.
- Heightened sense of smell – Some women notice increased sensitivity to certain odours.
Week 5
At 5 weeks pregnant, it becomes more real as changes in the body become more noticeable.
Key Developments This Week
Rapid Embryonic Growth
The embryo grows rapidly, and basic structures begin to form. The neural tube, which will develop the brain and the spinal cord, begins to close. The heart, which is still in its early stages of development, begins to beat. Other organs, such as the liver and kidneys, also form. At this stage, the embryo is 1-2 mm long.
Hormonal Shifts and Early Pregnancy Changes
HCG levels continue to rise, promoting the production of progesterone and estrogen, which help maintain the gravidity. These hormonal changes help the placenta and amniotic sac develop. They also cause noticeable symptoms early in pregnancy as the body adapts to the new condition.
Signs and Symptoms
- Missed period – One of the most common pointers of pregnancy.
- Morning sickness – Nausea, with or without vomiting, often triggered by certain smells.
- Fatigue – Rising progesterone levels may cause excessive tiredness.
- Frequent urination – Augmented blood flow to the kidneys principals to more frequent trips to the bathroom.
- Breast tenderness – Breasts may feel sore, swollen, or more sensitive than usual.
- Mood swings – Hormonal fluctuations can affect emotions, leading to sudden mood changes.
Do’s and Don’ts for the First 5 Weeks
Do’s
- Take prenatal vitamins – Folic acid is essential for the baby’s early development and helps prevent neural tube defects.
- Eat a balanced diet – Weakness in the first trimester is due to the rising Beta HCG hormone. Women are advised to consume more liquids, such as water, to help overcome this weakness. Excessive eating can lead to weight gain, which can be undesirable. The embryo needs hormonal support to grow.
- Stay hydrated – Drinking enough water can help digestion and prevent dehydration, which is common in early pregnancy.
- Get plenty of rest – Fatigue is common in the first few weeks, so allowing the body to recover is essential.
- Engage in gentle exercise – Light activities like walking or prenatal yoga may improve circulation and ease discomfort.
- Book a prenatal appointment – Early medical guidance can reassure and ensure the pregnancy progresses well.
- Manage stress – Practising relaxation techniques like deep breathing or meditation can help maintain emotional well-being.
Don’ts
- Avoid smoking, alcohol, and drugs – These substances can affect the baby’s development and increase the risk of complications.
- Limit caffeine intake – Too much caffeine may be linked to pregnancy complications, so it’s best to keep it in moderation.
- Do not take medication without medical advice – Certain over-the-counter and prescription drugs may not be safe during pregnancy.
- Avoid high-risk foods – Raw or undercooked meats, high-mercury fish, and unpasteurised dairy can increase the risk of infections. Avoid raw papaya and raw pineapple throughout the pregnancy as they can increase the risk of bleeding during pregnancy, cause premature uterine contractions and threaten an abortion.
- Avoid strenuous activities – Heavy lifting and penetrating workouts may strain the body unnecessarily.
- Do not ignore unusual symptoms – Severe cramping, heavy bleeding, or dizziness should be checked by a doctor as soon as possible.
Consult Today
The internal changes may be subtle during the first five weeks, but their significance is enormous. The proper organisation can make the difference for those going through this stage. At Max Hospital, our obstetricians and maternal-fetal medicine specialists are here to provide clarity and care at every stage, whether it’s confirming your pregnancy, addressing concerns, or planning for the weeks ahead. Consider booking a consultation if you’ve noticed the early signs or want more information.
Frequently Asked Questions
Is light spotting normal in early pregnancy?
Some spotting may be normal during the first few weeks of pregnancy and is usually caused by implantation bleeding, which occurs when the fertilised egg attaches to the endometrium. This usually happens around week 3 or 4 and is lighter than usual. However, it is recommended to seek medical attention if the staining is heavy, persistent, or accompanied by severe cramping.
How soon can an ultrasound detect pregnancy?
A transvaginal ultrasound can usually detect pregnancy as early as 5 to 6 weeks after your last period. Around this time, the gestational sac may be visible, and a heartbeat may sometimes be heard by the end of the sixth week. However, the mastery may vary depending on factors such as ovulation and implantation.
Can early pregnancy cause mood swings?
Yes, hormonal changes early in pregnancy can cause mood swings. Augmented levels of progesterone and estrogen can affect emotions, causing some people to feel more sensitive, irritable, or anxious. Fatigue and physical discomfort during the first few weeks can also contribute to mood swings.
What foods can help with fatigue?
Eating nutrient-rich foods can help combat fatigue in early pregnancy. Iron-rich foods like spinach, lentils, and lean meats help maintain energy levels, while complex carbohydrates like whole grains and oats provide sustained energy. Protein sources like eggs, nuts, and dairy can also help reduce fatigue. Staying hydrated and eating small, balanced meals throughout the day can help prevent energy slumps.
How much weight gain is expected up to 5 weeks of pregnancy?
You shouldn’t expect to gain much weight during the first five weeks of pregnancy. Some women may gain 1-4 pounds, while others may not notice any change. In some cases, nausea or food aversions may even cause a small amount of weight loss. Eating a balanced diet and having regular prenatal checkups can help you maintain healthy weight gain during pregnancy.