1st trimester of pregnancy: how many weeks is it?
The first trimester of pregnancy lasts 1 – 3 weeks total over a total duration of an average of 40 weeks or about 284 days. However, there are two ways to count the progression of a pregnancy: at the week of amenorrhea and at the week of gestation.
Week of Amenorrhea and Week of Pregnancy: What’s the Difference?
In health care, the running time calculation is based on the calculation of the date of the beginning of pregnancy, to which 9 months are added.
You should know that in a menstrual cycle, the luteal phase – the 2nd part of the cycle after ovulation – is the fixed period lasting 14 days, while the follicular phase is variable. As the midwife explains: “For a woman who has a regular 28-day cycle and her last menstrual period is March 1st, the onset of pregnancy is March 14th and the due date is December 14th. Whereas with a cycle of 34 days, the beginning of pregnancy is March 20th and the due date is December 20th.
If we start from the date of the first day of the woman’s last menstrual period, we speak of the period of amenorrhea. The weeks are then counted in weeks of amenorrhea, called SA.
If we want to count weeks of pregnancynamely the actual date of conception of the baby, it is advisable to subtract 2 weeks from these weeks of amenorrhea.
In the case of an irregular cycle, it is possible that the date of ovulation and therefore of fertilization is delayed: a dating ultrasound then makes it possible to precisely determine the date of conception.
When does the 1st trimester start?
“The first trimester of pregnancy therefore begins on the first day of the last menstrual period, if we speak of a week of amenorrhea (SA), or two weeks later if we speak of a week of pregnancy (SG),” summarizes the midwife.
When is the end of this term?
This first trimester ends at 13 completed weeks if we are counting weeks of pregnancy, or at 15 completed weeks if we are counting weeks of amenorrhea.
This 1st trimester is undoubtedly the one that marks the exponential development of the embryo and then the fetus. It starts very small Egg, which is the result of the fusion between the mother’s egg and the father’s sperm. Fertilization has taken place and the menstrual cycle stops. This leads to a change in the hormonal balance. In the ovary, the yellow body continues to produce estrogen and most importantly progesterone, which will play an important role in the continuation of the pregnancy, in particular by preventing the uterine contractions that could be the reason for ovulation. Progesterone also helps thicken the endometrium.
Barbara Forster, midwife: “Six to seven days after fertilization, the egg cell – also known as the blastocyst – has completed its migration from the fallopian tube to the uterus and can implant itself in the uterine lining, the endometrium.”
The nidation takes place at about 4 SA, the egg then resembles a raspberry and measures 4 to 5 millimeters. “During this implantation, the trophoblast villi surrounding the embryo, also called the blastocyte, disrupt the lining of the uterus to allow for the exchange of oxygen and nutrients. These villi will later become the placenta,” explains the midwife, and excrete the other important pregnancy hormone: Human Chorionic Gonadotropin (HCG).” This hormone enables pregnancy to be detected by a urine or blood test and also ensures the maintenance of the pregnancy,” says the midwife.
Implantation marks the transition from the egg to the embryo stage. HAS 6 SATthe embryo resembles a bean and his heart starts beating.
Out of 14 SATthe embryo gives way to it Fetus. His head, arms, legs are now clearly visible: he measures 45mm and weighs 10g. The stage known as organogenesis is complete. The formation of the organs and the establishment of the systems have been completed.
By the end of the first trimester, the fetus’s facial features are taking shape, it can have facial expressions, and it can suck its thumb. It then measures 85 mm from the head to the buttocks – we are talking about cranio-caudal length – and weighs 45 g.
Fatigue, nausea, constipation: the most common symptoms
The first trimester is shaped by many symptoms and inconveniences under the influence of hormones that can cloud this beginning of pregnancy for the expectant mother.
“The most common symptoms are nausea, Vomitassociated with disgust at smells, great tiredness and bouts of sleepiness, breast tenderness and constipation hormones‘ said the midwife. This trimester can also be characterized by frequent urinationfollowing the change in the axis of the uterus, which compresses the bladder.
In rare cases, the mother-to-be may suffer from hypersalivation, called hypersialorrhea, which results in twice the production of saliva than in normal times, which can amount to up to 2 liters per day!
“It’s been a physically and emotionally overwhelming trimester for the mother-to-be, who has often not officially disclosed her pregnancy to those around her – especially to the workforce – and who sometimes has to live with all of these inconveniences in secret. who can be very disabling for some women,” explains Barbara Forster, for whom it is important that women allow themselves to talk about their symptoms and their feelings.
In addition, the strong hormone fluctuations at the beginning of pregnancy often have an influence on the mood of the expectant mother, which can be subject to the emotional uplift.
Bleeding, Cramps, and Blood Loss: Should You Be Concerned?
The first months of pregnancy can be characterized by a stomach pain, causing tightness or cramps in the lower abdomen. If this pain can be physiological – related to the egg implantation, Pain we talk little or not at all aboutand the movements of the bones, abdominal muscles, and ligaments that move and move apart to make room for the fetus – It is always advisable to check that everything is in order.
Barbara Forster “The 1st trimester is the most sensitive and critical, it is important to check that everything is ok. There may be a risk of miscarriage or ectopic pregnancy”
Persistent pain or small bleeding should always be motivate a consultationin which a control ultrasound is proposed to the expectant mother to check the proper development of the fetus.
Which behavior in early pregnancy and what to look out for?
Although pregnancy may seem relatively abstract for the mother-to-be, whose body hasn’t really changed and who isn’t feeling her baby yet, it’s still on the right track and requires some precautions for its smooth operation.
“The 1st trimester is very delicate for the fetus and we now know that certain factors will play a role in the child’s future health,” emphasizes the midwife. Advice on nutrition, lifestyle, but also on the use of certain cosmetics or body products, certain colors or household products is helpful for the mother-to-be.
- Limit processed foods and junk foods,
- prefer fresh, seasonal and pesticide-free food,
- preferably choose organic cosmetics;
- and Escape from endocrine disruptors (Source 1) such as phthalates, bisphenol A, parabens etc.
- “As during the entire pregnancy, the consumption of alcohol and tobacco should ideally be stopped from the beginning of the pregnancy until the birth,” the midwife recalls.
Sports: which ones are allowed?
While it is important for pregnant women to maintain regular physical activity, care should be taken Protect the fetus from possible shock during the first months. Sports that are at risk of falling, such as horseback riding, skiing, skating, cycling or climbing, should be avoided. Also be careful with contact-prone sports such as handball, volleyball, basketball and of course all martial arts.
“Due to the risk of a gas embolism for the expectant mother, diving is absolutely contraindicated,” emphasizes Barbara Forster. And in general, an excessive increase in body temperature during physical activity should be avoided.
Recommended sports are Walking, swimming, pregnancy yoga, Pilates, stretching and gentle gymnasticsBe careful not to put too much strain on the waist belt.
Pregnancy exams in the first trimester
One of the first medical examinations proposed to the expectant mother in consultation is the realization of hers blood group chart – if not already available. Whether their rhesus is positive or negative, a search for irregular agglutinin – RAI – is performed to identify possible rhesus incompatibility between the mother and her baby.
“Then the mother-to-be has to make one serologyfor the toxoplasmosisthat rubellaSyphilis and hepatitis B, HIV, which can also be accompanied by hepatitis C,” says the midwife.
In case of’history of diabetes Family history, gestational diabetes in a previous pregnancy, BMI over 25, or age over 35: a fasting blood sugar is prescribed to pregnant women to screen for gestational diabetes.
“Depending on the medical history, a TSH test is offered to detect a thyroid dysfunction. And for women prone to urinary tract infections, a urine culture have to be carried out”, adds the midwife.
Around 12 weeks of amenorrhea, the long-awaited first ultrasound “This ensures that the baby is developing well in the uterus, that the baby is measured from head to bottom, that anomalies are detected and that the number of embryos is checked,” explains Barbara Forster.
Finally, that screening for Trisomy 21 can be performed between the 11th and 13th week of amenorrhea. It is reimbursed by social security but is not compulsory.
Weight Gain In The First Trimester: Should You Diet?
That weight gain during pregnancy has been the subject of much debate, and perhaps a source of stress for the mother-to-be. “Every woman is differentit is necessary to adapt to the specificities of each individual and to personalize the advice,” assures Barbara Forster. In particular, the midwife recalls that the woman’s pre-pregnancy BMI must be taken into account to determine her appropriate weight gain. .
Nutritional support is not the same for a low BMI mother and another whose BMI is over 25.
Whatever happens, it is important for the mother-to-be to be attentive contents of his platenot necessarily to limit weight gain, however to provide the fetus with everything it needs and spare him everything that is not good for him. “As the saying goes: You don’t eat for two, but twice as well,” remembers Barbara Forster. It is important to eat “healthy”.
So the pregnant woman can prefer fresh fruit and vegetables Seasonal, whole grain products, legumes, seeds and oilseeds, vegetable oils such as rapeseed oil, which is rich in omega-3 fatty acids, lean meat and oily fish (e.g. mackerel, sardines). However, be careful big fish such as tuna, swordfish, salmon or similar
Pike, potentially rich in heavy metalswhich should be limited during pregnancy.
Ultra-processed foods full of additives and preservatives are sensibly restricted throughout pregnancy, but even more so during this 1st trimester.
Finally, staying hydrated during pregnancy is even more important than normal: expectant mothers are advised to drink at least 1.5 liters of water a day.