How does your body change at the start of pregnancy? A guide to the first few weeks.

The first few weeks of pregnancy are a time full of new experiences, but also of doubts. Often, the changes begin even before you realise you’re pregnant, and it’s normal to wonder whether what you’re feeling is normal, how many weeks along you are, or what’s happening inside your body. In this guide, we explain how pregnancy weeks are counted, what happens in your body at the start, how the first trimester progresses week by week, and which changes during pregnancy are normal and which ones you should seek advice about.

How do you know how many weeks pregnant you are?

Pregnancy weeks are not counted from the day of conception, but from the first day of your last period. This is the method universally used in healthcare systems because it is a date that almost all women know, whereas the exact day of conception is difficult to determine.

This means that, during the first two weeks of pregnancy, your body is actually preparing for ovulation. Conception usually takes place about two weeks after the start of your period. Therefore, when you notice that your period is late, you’ll already be approximately four weeks pregnant. If your cycles are irregular or you cannot remember the date of your last period, a first-trimester ultrasound scan is the most accurate way to confirm how many weeks pregnant you are.

As an initial guide at home, you can use pregnancy tests, such as the Clearblue Digital Test with Weeks Indicator, which, as well as detecting pregnancy, tells you how many weeks have passed since conception: 1–2, 2–3 or more than 3. It detects pregnancy with over 99 per cent accuracy from the day your period is due, and the weeks indicator is 93 per cent accurate. If you take the test before your period is due, use your first urine of the morning for a more reliable result, as hormone levels are highest at this time. Bear in mind that the test counts the weeks from conception, not from your last period. To work out how many weeks pregnant you are, you’ll need to add two weeks to the result. So, if the test shows 2–3, you’ll be approximately four to five weeks pregnant.

The first weeks of pregnancy: what’s happening in your body

During pregnancy, the first few weeks are when the most hormonal changes occur, although you may not notice anything on the outside. As soon as the fertilised egg implants in the womb, your body starts producing the hormone human chorionic gonadotrophin (hCG), which is the same hormone detected by pregnancy tests. At the same time, levels of progesterone and oestrogen rise, which prepare the womb and are responsible for many of the symptoms experienced during these first few weeks.

As a result, the most common early signs are:

• A missed period, which is usually the first clue.
• Breasts that are more sensitive, swollen or tender, and darker areolas.
• Fatigue and drowsiness, sometimes very severe.
• Nausea and, occasionally, vomiting. These usually appear around the sixth week and can occur at any time of day.
• The need to urinate more frequently.
• Increased sensitivity to smells and changes in taste, or aversion to certain foods.
• Abdominal bloating, wind and constipation.
• Mood swings
• Light spotting, which may occur when the embryo implants in the womb.

Not all women experience all these symptoms, nor do they experience them with the same intensity. Experiencing few symptoms is also normal and does not indicate that anything is wrong.

Remember that if you’re trying to conceive or have just found out you’re pregnant, you should take folic acid, ideally from before conception, to help prevent neural tube defects. It’s also important to consult your doctor or midwife before taking any supplements.

First trimester of pregnancy: a week-by-week guide

The first trimester of pregnancy lasts until the end of week 12 and is the stage during which the baby’s organs form. These are the key stages:

• Weeks 1–4:

Fertilisation and implantation of the embryo in the womb take place, and hCG production begins. This is the week when a missed period usually occurs and a pregnancy test may show a positive result.

• Weeks 5–10 (Embryonic period):

The brain, spinal cord, heart (which begins to beat) and the main organs and limbs form. The embryo is now referred to as a foetus.

• Week 12:

The first first-trimester ultrasound scan is carried out, which confirms the gestational age and forms part of the screening for chromosomal abnormalities.

Changes during pregnancy: what’s normal and what isn’t

Most changes during the first few weeks of pregnancy are normal and form part of your body’s adaptation. It is common to experience nausea, tiredness, tender breasts, mild discomfort or twinges in the lower abdomen, changes in vaginal discharge, constipation, heartburn or occasional light spotting. However, there are symptoms you should not ignore. Always remember to see your doctor or go to A&E if you notice:

• Heavy vaginal bleeding, like a period, or bleeding with clots.
• Severe abdominal pain, or pain on one side only.
• Vomiting so frequent that you are unable to keep down any fluids or food.
• Fever.
• A burning sensation or pain when urinating.
• Severe dizziness or fainting.

The first few weeks of pregnancy are a time of many changes, but also of great excitement. Listen to your body, look after yourself and don’t hesitate to ask for help when you need it. At Farmaciasdirect, we’re here to support you right from the start: if you have any questions about pregnancy tests or any products for this stage, please consult our team of pharmacists.