What is basal body temperature? Pregnancy and basal body temperature (BBT)

The basal body temperature is the body’s lowest temperature. It can be measured whilst at rest, usually in the morning upon waking. Throughout a woman’s menstrual cycle, her basal body temperature changes. During the (between periods and ovulation), the basal body temperature is generally between 36.1 °C and 36.5 °C. Following ovulation, the corpus luteum begins to produce oestrogen and the temperature rises slightly as a result to around 37 °C in In a typical cycle, the temperature rises slightly after ovulation and remains at a plateau during the luteal phase, until menstruation begins. However, in the event of pregnancy, progesterone levels remain high and keep the basal body temperature at a high plateau. This explains why accurate measurement of basal body temperature is a reliable indicator of pregnancy. Would you like to find out more? Check out our articles on the subject:

Which early pregnancy symptoms can appear before your period?

By Marine Leleux

Published on: Thursday, March 28, 2024, Updated on: Thursday, October 08, 2026

The start of pregnancy is accompanied by various signs even before a missed period occurs. Early pregnancy symptoms can vary from woman to woman. However, this period full of anticipation is usually associated with a variety of subtle clues! Do you think you might be pregnant? Follow our guide to discover the most common signs of pregnancy.

Contents

In brief

The early signs of pregnancy before a missed period vary: tender breasts, morning sickness, frequent urges to urinate, mild lower abdominal pain, or even strong food cravings or aversions.
These symptoms can resemble those of premenstrual syndrome, which makes them difficult to interpret; the only reliable way to confirm a pregnancy is still a urine or blood test, the latter being more reliable.
The article points out that every woman experiences these signs differently and that certain symptoms may appear earlier or later, hence the importance of listening to your body and its signals.

What happens in early pregnancy?

The start of pregnancy triggers a cascade of hormonal changes in the expectant mother. At the moment of fertilisation, the egg meets the sperm in the fallopian tube to form the first cell of the baby’s body: the zygote.

A few days after fertilisation, the zygote begins to divide and implants itself into the uterine lining. This cluster of cells is commonly known as the blastocyst. Its implantation marks the start of the production of human chorionic gonadotrophin (hCG), a hormone essential for maintaining healthy levels of progesterone during early pregnancy. The process of implantation in the uterus is called nidation.

The early stages of pregnancy are accompanied by hormonal fluctuations in women, particularly relating to the balance between oestrogen and progesterone. These changes lead to a variety of physiological signs: the first symptoms of pregnancy.

When do pregnancy signs appear?

The first symptoms of pregnancy begin to appear when the blastocyst implants itself in the uterine lining, under the influence of the hormone hCG. For some women, pregnancy symptoms appear 1 to 2 weeks after conception! For other mums, the signs appear a little later.

How can you tell if you’re pregnant before your period is due?

A missed period is a key indicator of early pregnancy! However, there are various early signs of pregnancy that can help you tell if you’re pregnant well before your period is due.

A pulling sensation in the lower abdomen: At the time of implantation, it is common to feel pressure in the lower abdomen. This pulling sensation can be mistaken for the well-known PMS (Premenstrual Syndrome), which can cause similar effects. In most cases, the implantation of the blastocyst in the uterus is not painful. However, a pregnant woman may experience some uncomfortable pressure in her lower abdomen.

Breast tenderness: A common early sign of pregnancy is breast tenderness. If you are pregnant, your breasts may become swollen or tender as early as the first few weeks after conception. In some expectant mothers, an increase in breast size can already be noticed as early as the second week of pregnancy.

Food cravings: Fancy some strawberries? You might be pregnant! Many expectant mothers experience strong food cravings or food aversions right from the start of pregnancy. These feelings are usually sudden and intense. Conversely, certain foods may become very appealing and lead to strong cravings.

Headaches: The hormonal fluctuations associated with changes in blood circulation in pregnant women can lead to headaches. These headaches are generally mild and occur only occasionally. If you experience regular headaches, please do not hesitate to discuss this with your GP.

Skin changes: The texture of our skin is closely linked to our hormonal balance. When progesterone levels rise in an expectant mother’s body, skin changes may occur. Many women find that their skin becomes drier or notice the appearance of pregnancy spots or pigmentation spots on their face.

Mood swings: It is common for pregnant women to experience emotions more intensely than usual. If you’re feeling particularly emotional, this is perfectly normal! Once again, hormonal fluctuations are the cause of this early sign of pregnancy.

Changes in bowel movements: One of the first signs of pregnancy is a change in bowel movements. In most cases, digestion is slowed down by increased levels of progesterone in the blood. Many expectant mothers experience episodes of constipation in early pregnancy. Generally, bowel movements return to normal after a few weeks.

Frequent urination: Following the baby’s implantation, the blood volume increases in the expectant mother’s body. This change, typical of the first few weeks of pregnancy, is essential for the health of the uterine lining. This physiological change puts increased pressure on the bladder, which can lead to frequent trips to the toilet!

Morning sickness: pregnancy sickness is well known! It is certainly a clear sign, particularly when it occurs in the morning upon waking. However, nausea usually appears later than other early signs of pregnancy. For most women, nausea sets in between the 4th and 6th week of pregnancy.

Period symptoms or pregnancy symptoms: what’s the difference?

The first signs of pregnancy can easily be confused with certain symptoms of PMS (Premenstrual Syndrome). It can be tricky to tell whether your period is on its way or whether you’re expecting a baby! The main difference? Signs of pregnancy persist, whereas PMS symptoms are temporary. The best way to find out where you stand is to take a pregnancy test.

Can I take a pregnancy test before my period is due?

The best way to find out if you’re pregnant is to get a pregnancy test! Pregnancy tests sold in pharmacies can be used at home. They reliably detect pregnancy by identifying the presence of the hCG hormone. It is recommended that you take the test first thing in the morning upon waking as this is the time of day when your urine has the highest concentration of hCG. You can also contact your GP to ask for a blood test. A blood test is the most reliable way to find out if you are pregnant!

Find out everything you need to know about the Menstrual cycle: understanding the ovulatory phase and supporting it naturally

Expert advice

If you’re hoping to get pregnant, you’re no doubt on the lookout for potential signs! It’s good for women to listen to their bodies and navigate their cycles with a clear understanding of what’s happening. Tracking your hormonal changes throughout your menstrual cycle is an excellent way to know where you stand and to respect your body’s natural needs. There are various methods for tracking the female menstrual cycle, such as the symptothermal method

Spotlight on Our Naturopathic Writer: Marine Leleux

Marine is a naturopath specialising in children's well-being and a parenting coach. With 10 years' experience in supporting families, she draws on her experience to help her community by sharing natural, caring advice.