Week 1: The Cycle Begins

Week 1 of pregnancy is counted from the first day of your last menstrual period. That means you're not technically pregnant yet! This method is used by doctors and midwives worldwide to calculate your due date, and it is the standard across modern prenatal care.

Your body is getting ready for a new cycle — and perhaps a new baby. Even though nothing has happened yet, this week matters because it sets the starting point for your entire pregnancy journey. Everything that happens from now on counts toward the 40 weeks of pregnancy.

A pregnancy lasts an average of 40 weeks, counted from this day. You can use a due date calculator to estimate your expected delivery date based on the date of your last period.

Baby's Development

No embryo yet: Fertilization doesn't happen for about two more weeks, so there is no embryo at this point
Egg cell matures: In your ovaries, several follicles are maturing, and one will become the dominant follicle that releases an egg at ovulation
Uterine lining builds up: The uterus prepares a soft, nutrient-rich lining where a fertilized egg can implant
Nature gets ready: Your entire reproductive system is working to create the right conditions for a possible fertilization
Hormones drive the process: The hypothalamus in your brain sends signals that start the whole cycle via GnRH hormone

Why Pregnancy Is Counted From the Last Period

Healthcare providers use what is known as Naegele's rule to calculate your due date: the first day of your last period plus 280 days (40 weeks). The reason is simple — most people remember the date of their last period, while the exact moment of fertilization is difficult to pinpoint.

This counting method means that in weeks 1 and 2 you are not technically pregnant, but those weeks still count in the pregnancy calculation. When you have your first ultrasound around weeks 11–14, the due date may be adjusted based on the baby's size. Ultrasound measurements are more accurate than calculations based on the last period, especially for people with irregular cycles.

The due date is always just an estimate — most babies are born within a window of two weeks before or after.

Your Body

Menstruation: You have your period as normal. This is the start of a new cycle
Hormones at work: Estrogen and FSH (follicle-stimulating hormone) begin to rise to mature the eggs
Uterus renews itself: The lining from the previous cycle is shed, and a new, fresh lining will build up
You may notice nothing special: Since you are not pregnant yet, you will not have any pregnancy symptoms
Normal cycle length: A normal menstrual cycle lasts 21–35 days, with an average of 28 days
Duration of bleeding: Menstruation usually lasts 3–7 days, and the amount of bleeding varies from person to person

Menstrual Cycle and Hormones

The menstrual cycle is controlled by an interplay of hormones. FSH (follicle-stimulating hormone) starts the maturation of follicles in the ovaries, while estrogen from the growing follicles builds up the uterine lining. When estrogen levels are high enough, a surge of LH (luteinizing hormone) triggers ovulation.

After ovulation, the corpus luteum produces progesterone, which keeps the lining stable and ready for a fertilized egg. If fertilization doesn't occur, progesterone drops and the lining is shed as menstruation.

The cycle is divided into three phases:

Follicular phase (day 1 to ovulation): Follicles mature under the influence of FSH
Ovulation (typically around day 14 in a 28-day cycle): A mature egg is released
Luteal phase (from ovulation to menstruation): The corpus luteum produces progesterone for about 14 days

Good to Know

If you are planning to become pregnant, this is a perfect time to start taking folic acid. According to the WHO and ACOG, 400 micrograms of folic acid daily is recommended, ideally starting at least one month before conception and continuing through the first trimester. Folic acid protects against neural tube defects such as spina bifida.

It is also wise to cut out alcohol now. According to the CDC and WHO, there is no known safe amount of alcohol during pregnancy. The earlier you stop, the better it is for the baby. The same applies to smoking — health authorities universally recommend stopping all tobacco use before trying to conceive.

Eat a varied, nutritious diet, stay active, and get enough sleep. A healthy lifestyle before conception provides the best foundation for a good pregnancy. Major health organizations recommend at least 150 minutes of moderate physical activity per week — this also applies during pregnancy.

Also check that your vaccinations are up to date. Talk to your doctor about rubella and other vaccines that should be in place before you become pregnant. Some vaccines, such as the MMR vaccine, cannot be given during pregnancy, and it is recommended to wait at least four weeks after vaccination before trying to conceive.

If you use the pill or other hormonal contraception, speak with your doctor about when to stop. For most people, it is safe to try conceiving from the first cycle after stopping. IUDs must be removed by a healthcare provider.

Supplements and Vitamins

The following supplements are widely recommended for people planning to conceive:

Folic Acid

400 micrograms daily, starting at least one month before conception. Folic acid occurs naturally in dark leafy greens, beans, lentils, and whole grains, but supplements are recommended because it is difficult to get enough through diet alone. Folic acid is critical for the neural tube (which becomes the brain and spinal cord) to develop normally. People who have previously had a baby with a neural tube defect should take 4 mg daily — discuss this with your doctor.

Vitamin D

10–15 micrograms (400–600 IU) daily is commonly recommended for most adults. Vitamin D is important for calcium absorption and for the baby's bone and dental health. Good dietary sources include fatty fish, fortified dairy products, and egg yolks.

Iodine

Important for thyroid function and the baby's brain development. Good sources are dairy products, eggs, and fish. Many people do not get enough iodine through diet alone, so supplementation may be appropriate — discuss this with your healthcare provider.

Iron

Iron needs increase during pregnancy because blood volume increases. Good sources include lean red meat, beans, lentils, and whole grains. Iron levels are typically checked at the first prenatal appointment.

Talk to your doctor about any other supplements that may be right for you.

Diet and Nutrition

A good diet before pregnancy lays the foundation for a healthy pregnancy. Focus on:

Vegetables and fruit: At least 5 portions daily for vitamins, minerals, and fiber
Whole grains: Oats, whole wheat bread, brown rice — provide lasting energy and fiber
Fish: 2–3 portions per week, including fatty fish like salmon and mackerel for omega-3
Lean meat and eggs: Good protein sources that also provide iron and B vitamins
Beans and lentils: Excellent sources of protein, iron, folic acid, and fiber
Dairy products: Provide calcium and iodine

Limit processed foods, sugar, and saturated fat. Drink plenty of water — at least 1.5 liters daily.

Exercise and Physical Activity

Being in good physical shape before pregnancy has many benefits. Aim for at least 150 minutes of moderate activity per week:

Walking: Simple and effective — suitable for most people
Swimming: Gentle on the joints and provides a full-body workout
Strength training: Focus on core muscles, back, and pelvic floor
Pelvic floor exercises: Start now — a strong pelvic floor makes pregnancy more comfortable and speeds up recovery after birth
Yoga and pilates: Build strength, flexibility, and mental calm

People who are physically active before pregnancy generally have smoother pregnancies, shorter labors, and faster recovery.

Vaccinations and Health Checks

Before trying to conceive, consider checking the following:

Vaccines

Rubella (German measles): Most people are vaccinated in childhood, but you can check your immunity with a blood test. Rubella during pregnancy can cause serious fetal defects
Chickenpox: If you have never had chickenpox, consider vaccination — the vaccine cannot be given during pregnancy
Flu vaccine: Recommended for pregnant people during flu season
COVID-19: Stay up to date on COVID-19 vaccination per current guidelines
Whooping cough (pertussis): Vaccination during pregnancy is often recommended to protect the newborn

Health Check With Your Doctor

Review any chronic conditions (diabetes, thyroid disease, epilepsy)
Medication review — some medications need to be changed before pregnancy
Blood tests to check iron levels, thyroid, and immunity
Discussion about lifestyle, diet, and weight
Dental check — hormonal changes during pregnancy can affect the gums

Mental Health and Preparation

Planning a pregnancy involves more than physical preparation. Mental health matters equally:

Talk About Expectations

Discuss with your partner your expectations about parenthood
Talk about finances, living arrangements, and division of responsibilities
Be open about concerns and uncertainty — it is completely normal to have mixed feelings

Stress Management

Find good routines for relaxation — yoga, meditation, or walks in nature
Get enough sleep — most adults need 7–9 hours
Limit caffeine — major health bodies recommend a maximum of 200 mg of caffeine per day during pregnancy (about 2 cups of coffee)
Stay connected with friends and family — social support is important for wellbeing

Previous Mental Health Challenges

People with a history of depression, anxiety, or other mental health conditions should speak with their doctor before pregnancy. Some medications may need adjusting, and a plan can be put in place for support throughout the pregnancy.

Antenatal Care — An Overview

It can be helpful to know what to expect in prenatal care:

Weeks 8–12: First prenatal appointment with doctor or midwife
Weeks 11–14: First trimester screening (nuchal translucency ultrasound + blood tests)
Weeks 18–20: Anatomy scan — detailed examination of the baby's organs
About 8–12 appointments total: More frequent toward the end of pregnancy
Weeks 36–40: Weekly check-ups

Learn more about what to expect week by week in the pregnancy timeline.

Environmental Factors to Be Aware Of

Be mindful of certain environmental factors when planning pregnancy:

Chemicals and Substances

Smoking: Quit all tobacco. Avoid secondhand smoke
Alcohol: Zero alcohol is the safest approach according to CDC and WHO
Pesticides: Wash fruit and vegetables thoroughly. Choose organic where possible
Cleaning products: Wear gloves and ensure good ventilation when using strong cleaning agents
Hair dye and nail polish: Limit use of products with harsh chemicals

Work Conditions

Some occupations involve exposure to chemicals, radiation, or heavy lifting
Speak with your occupational health provider or doctor if you are unsure about workplace risk factors
You have the right to workplace adjustments during pregnancy under employment law

Pets

Cats can carry the toxoplasmosis parasite — have someone else empty the litter box
Avoid contact with sheep and goat births
Dogs are generally safe to be around as normal

For Your Partner

Get involved in the preparations — start reading about pregnancy together
Consider cutting back on alcohol and eating healthier as well — it makes it easier for both of you
Schedule your own health checks — dental, GP, and blood tests
Read up on the pregnancy timeline together so you know what to expect
Talk openly about expectations and concerns — good communication matters from the very beginning

Tips for Week 1

Start folic acid: 400 micrograms daily is recommended by WHO and ACOG, starting at least one month before conception
Cut alcohol and smoking: There is no known safe amount of alcohol during pregnancy
Track your cycle: Use a cycle-tracking app or calendar to keep track of your menstrual cycle
Review your medications: Some drugs are not safe during pregnancy — speak with your doctor if you take any regular medications
Check your dental health: Book a dental appointment — good oral health matters because hormones can affect the gums during pregnancy
Make a plan: Use a checklist to keep track of what to do before you conceive

When to Contact a Doctor

Contact your doctor or midwife if you experience:

Very heavy or unusual menstrual pain
Bleeding between periods
Irregular cycles that make it difficult to plan
You have been trying to conceive for over a year without success (six months if you are over 35)
You take regular medications and are unsure whether they are safe during pregnancy
You have chronic conditions such as diabetes, epilepsy, or thyroid disease — these should be optimized before conception

Did You Know?

Pregnancy is counted from the first day of the last period, which means you are technically "pregnant" for two weeks before fertilization actually happens!
A woman is born with all the eggs she will ever have — about 1–2 million. By puberty, around 300,000–400,000 remain, and only about 400 of these will mature and be released during her lifetime.
Folic acid was first isolated from spinach leaves in 1941. The name comes from the Latin word "folium," meaning leaf.
The fertile window in a cycle is only about 6 days long. The timing of intercourse in relation to ovulation is the most important factor in the chance of conceiving.
The neural tube — the structure that becomes the brain and spinal cord — develops very early in pregnancy, often before you know you are pregnant. This is why starting folic acid early matters so much.
The uterine lining renews itself completely in every menstrual cycle — an impressive biological process.

Frequently Asked Questions About Week 1

Am I really pregnant in week 1?

No, technically you are not pregnant yet. Week 1 is counted from the first day of your last period, and fertilization usually does not occur until around week 3. This counting method is used in prenatal care because most people know the date of their last period, while the moment of fertilization is harder to determine.

Do I need to take folic acid before I get pregnant?

According to WHO and ACOG, it is recommended to start 400 micrograms of folic acid daily at least one month before you plan to conceive. The neural tube, which develops into the brain and spinal cord, forms very early in pregnancy — often before you know you are pregnant. Having good folic acid levels in your body from the start is therefore important.

How long does it typically take to get pregnant?

For healthy couples under 35, the chance of getting pregnant in any given cycle is around 20–25 percent. Most couples conceive within one year with regular trying. Contact your doctor if you are under 35 and have been trying for one year, or over 35 and have been trying for six months, without success.

Can I drink alcohol while we are trying to conceive?

The safest approach is to cut out alcohol entirely when planning a pregnancy. Since you do not know exactly when fertilization will occur, you could be pregnant for a few weeks without knowing it. CDC and WHO recommend zero alcohol during pregnancy because there is no known safe amount.

Which medications should I avoid when trying to conceive?

Some medications can be harmful to a developing embryo. This includes certain acne medications (isotretinoin), some epilepsy medications, blood thinners, and certain psychiatric drugs. Never stop medications on your own — always speak with your doctor about whether it is safe to continue or whether you need to switch.

Should I take vitamin D in addition to folic acid?

Vitamin D is recommended for most adults — around 10–15 micrograms (400–600 IU) daily. Vitamin D is important for calcium absorption and for the baby's bone and dental health. It is especially important during winter months when sun exposure is limited.

How important is weight and BMI before pregnancy?

A healthy weight before pregnancy provides the best foundation for an uncomplicated pregnancy. Both underweight and overweight can affect fertility and increase the risk of complications. Speak with your doctor if you are unsure whether weight is something to address.

How much caffeine can I drink?

During pregnancy, major health organizations recommend limiting caffeine to a maximum of 200 mg per day, which is roughly two cups of filtered coffee. Too much caffeine may affect the developing baby. It can be helpful to start cutting back now. Remember that caffeine is also found in tea, cola, energy drinks, and chocolate.

Is it safe to dye my hair or use self-tanner?

Research suggests that hair dye is safe after the first trimester. Ammonia-free products are recommended, and good ventilation is important. There is limited research on self-tanning during pregnancy, but most experts consider self-tanning cream (not spray) to be safe, as it only affects the outermost layer of skin.

Should my partner take folic acid?

Folic acid is primarily recommended for people who are planning to conceive, to protect against neural tube defects. While there is no universal recommendation for male partners to take folic acid, a generally healthy diet rich in vegetables and whole grains supports sperm quality.

Next week: Ovulation approaches, and the fertile window opens!