Week 1
This is the week of your period, and you are not pregnant yet. That sounds odd in a pregnancy book, but it is how pregnancy is counted almost everywhere: from the first day of your last menstrual period, about two weeks before conception. So when you hear "eight weeks pregnant", the embryo itself is only about six weeks old. Through weeks 1 to 4, keep that two-week gap in mind.
Your body is quietly resetting. The old uterine lining sheds, and hormones from your brain start ripening a new batch of eggs. If you are reading this after a positive test, think of this week as background. If you are planning, it is a good time to start folic acid, look at your medications, and get any health conditions checked.
Day 1 · 0 weeks 0 days
Your pregnancy is counted from your last period
Day 1 of this book is the first day of your last menstrual period, the first day of real bleeding rather than spotting. Your care provider will almost certainly ask you for this date. It is the starting point for your due date and for every "weeks pregnant" figure you will hear.
Why start before you are pregnant? Because the date of conception is rarely known for sure, while most people can recall when their period started. Counting from that day gives everyone a shared, simple clock. It assumes ovulation around day 14 of a 28-day cycle, with conception soon after.
This means the age of your pregnancy and the age of your baby are two different numbers. Gestational age, the one used in clinics and in this book, runs about two weeks ahead of the embryo's actual age. A pregnancy described as 4 weeks along holds an embryo that is about 2 weeks old. The full count runs to 40 weeks, or 280 days, from day 1. That is a little over nine calendar months. In this book, each day has its own entry, labelled with the day number and the gestational age, so you always know where you are.
Try this: Write down the first day of your last period somewhere you will find it again, such as your phone's notes or a calendar.
Day 2 · 0 weeks 1 day
A due date is a best guess, not a deadline
To estimate a due date, add 280 days to the first day of your last period. A quick shortcut is to add one year, take away three months, and add seven days. If your period started on March 10, your estimated due date is around December 17.
That date marks 40 weeks exactly. In this book, day 280 is the last day before it. Online calculators and pregnancy wheels all use the same basic method, so they should agree within a day.
Only about 1 in 20 babies arrives on the due date itself. Most are born somewhere between 37 and 42 weeks, and that whole span is normal. It helps to think of a "due month" rather than a single day, especially when friends and family start asking.
Your date may also shift. An early ultrasound measures the embryo and can give a more accurate estimate, particularly if your cycles are long or irregular or you are unsure of your period date. If the scan and your period date disagree by more than a few days, your care provider will usually go by the scan. That is normal, not a sign of a problem.
Try this: Work out your estimated due date with the shortcut, then pencil in the whole month around it rather than one circled day.
Day 3 · 0 weeks 2 days
Your cycle is a monthly rehearsal for pregnancy
Each menstrual cycle prepares your body for a possible pregnancy. When no pregnancy happens, the lining of the uterus sheds as your period, and the process starts over. Understanding the pattern makes the next few weeks easier to follow.
The cycle has two main halves. In the first, the follicular phase, hormones from the pituitary gland at the base of your brain prompt several follicles in your ovaries to grow. Each follicle is a small fluid-filled sac holding an immature egg. As they grow, they release estrogen, which rebuilds the uterine lining.
Around the middle of the cycle, one egg is released. This is ovulation. The second half, the luteal phase, follows. The empty follicle turns into a structure that makes progesterone, which keeps the lining thick and ready to receive a fertilized egg.
Cycles vary. Anything from about 21 to 35 days is common, and the length can change from month to month. The second half is usually the more stable one, at roughly 12 to 14 days. So in a longer cycle, ovulation tends to come later, and in a shorter one, earlier. This is why the "day 14" rule is only an average.
Try this: If you track your cycle, look back at your last few cycle lengths. Knowing your usual range will help you and your care provider later.
Day 4 · 0 weeks 3 days
Folic acid works best when you start early
Folic acid is the one supplement almost every expert agrees on before and during early pregnancy. It is the synthetic form of folate, a B vitamin. Taking it lowers the chance of neural tube defects, such as spina bifida, where the baby's spine or brain does not form properly.
Timing is the key. The neural tube, which becomes the brain and spinal cord, forms and closes very early, around six weeks of pregnancy as counted in this book. Many people do not know they are pregnant until it is nearly done. That is why the advice is to take folic acid from before conception if possible.
The usual recommendation is 400 micrograms a day, ideally starting at least a month before you try to conceive, and continuing until at least 12 weeks. If you are already pregnant and have not started, start today. It still helps.
Some people need a higher dose. This includes people with diabetes, those taking certain epilepsy medications, people with a higher body weight in some guidelines, and those with a previous pregnancy affected by a neural tube defect. A higher dose needs a prescription or clear advice from your care provider, so ask rather than guessing.
Leafy greens, legumes, and fortified grains also contain folate, but food alone is not enough here.
Try this: Buy a folic acid supplement or a prenatal vitamin that contains 400 micrograms, and keep it next to your toothbrush so you remember it.
Day 5 · 0 weeks 4 days
A prenatal vitamin covers the basics, not everything
A prenatal vitamin is a simple way to get folic acid plus a few other nutrients that matter in pregnancy. It is a safety net, not a replacement for food. You do not need an expensive brand. Look at the label rather than the price.
Useful things to look for include folic acid at 400 micrograms, iodine for the baby's brain and thyroid development, vitamin D for bones, and some iron. Your care provider may suggest extra vitamin D or iron depending on your blood tests, your diet, and where you live.
There are also things to avoid. Do not take high-dose vitamin A supplements, or fish liver oils that contain vitamin A, as too much retinol can harm a developing baby. Prenatal formulas are designed to stay below risky levels. Also avoid stacking several multivitamins, which can push some nutrients too high.
If your vitamin makes you queasy, try taking it with food or at bedtime. Some people find a chewable or smaller tablet easier. If you follow a vegan diet, check that your prenatal includes vitamin B12, or ask about a separate supplement.
Try this: Read the label on your vitamin and check for folic acid, iodine, and vitamin D, and that it is not a high-dose vitamin A product.
Day 6 · 0 weeks 5 days
Take a fresh look at what you take every day
Before or early in pregnancy, it is worth reviewing every medicine you use. That includes prescriptions, over-the-counter products, creams, herbal remedies, and supplements. Most are fine, some need a switch, and a few should be stopped.
Do not stop a prescribed medicine suddenly on your own. For conditions like epilepsy, depression, anxiety, asthma, high blood pressure, or thyroid disease, stopping can be riskier for you and your baby than continuing. Your prescriber can weigh the options and often move you to a medicine with a better safety record in pregnancy.
A few medicines are known to carry real risks, such as some acne treatments (isotretinoin and retinoid creams), valproate for epilepsy or mood, and certain blood thinners and blood pressure medicines. If you take any of these and are pregnant or trying, contact your prescriber soon. For everyday aches and fevers, acetaminophen (paracetamol) is generally considered the preferred choice in pregnancy, used as directed on the package. Anti-inflammatory painkillers such as ibuprofen are usually avoided, especially later in pregnancy, unless a care provider advises them. Herbal products are not automatically safe, and many have little safety data.
A pharmacist is a free, easy-to-reach expert for these questions. Try this: Make a list of everything you take, with doses, and ask a pharmacist or your prescriber to go through it with you.
Day 7 · 0 weeks 6 days
Long-term health conditions deserve an early conversation
If you live with an ongoing health condition, the best time to talk about pregnancy is before it starts, or as soon as you know. Good control in the early weeks can make a real difference.
Diabetes is a clear example. Blood sugar that is well managed around conception lowers the risk of miscarriage and of some birth differences. Thyroid conditions often need a dose change early in pregnancy, because demand for thyroid hormone rises. High blood pressure, epilepsy, kidney disease, autoimmune conditions, and mental health conditions all benefit from a plan made with your care team.
A pre-pregnancy check-up, if you can get one, is a chance to review your medicines, update your vaccines, and talk through any past pregnancy problems. Some vaccines, like those for measles, mumps, and rubella or chickenpox, should be given before pregnancy rather than during it, so this conversation matters for timing.
If you are already pregnant, do not worry that you missed the window. Contact the person who manages your condition now and let them know. They are used to adjusting plans quickly.
For your partner: Offer to come along to any pre-pregnancy or specialist appointment, and help keep a list of questions so nothing gets forgotten.