Pregnancy begins during fertilization, ie the meeting of the oocyte and a sperm. Once entered into the oocyte, the nucleus of the sperm increases in size, as does the nucleus of the oocyte. The two come together and eventually merge: thus born the zygote, the first cell at the origin of all life. This egg carries all the genetic material necessary to build a human being.

About thirty hours after fertilization begins segmentation: the zygote divides several times, while migrating to the uterine cavity. Nine days after fertilization takes place implantation: the egg is implanted in the uterine lining.

At the 3rd week of pregnancy, the egg has become an embryo, her heart begins to beat. It then measures 1,5 mm and its cells continue to divide and begin to differentiate according to the organs.

At the end of this first month of pregnancy, the 1 month embryo measures approximately 5 mm. It has a distinct “head” and “tail”, the buds of its arms, inner ear, eye, tongue. Organogenesis has started and the fetal-maternal circulation is in place. Pregnancy is visible on ultrasound at 1 month and the heartbeat is noticeable (1) (2).

As a life begins in her body, the mother ignores it the whole time 1st month of pregnancy. It is only with the delay of menstruation at 4 weeks that pregnancy is suspected. The 1-month-old embryo, which will become a fetus, has already two weeks of life.

Very quickly, however, the mother’s body will undergo intense transformations under the effect of the hormones of pregnancy: the hCG secreted by the trophoblast (outer layer of the egg) which in turn keeps the corpus luteum active. (from the follicle) which secretes progesterone, essential for the proper implantation of the egg.

This hormonal climate can already lead to different symptoms of pregnancy during the 1st month :

• nausea
• sensitivity to odors
• a swollen and tight chest
• some irritability
• drowsiness during the day
• frequent urges to urinate

The uterus is growing: the size of a walnut outside of pregnancy, it is now the size of a clementine. This increase in volume can lead to tightness, even pain in the lower abdomen during the 1st month of pregnancy. 

The belly of a 1 month pregnant woman is not yet visible, but it will gain volume month by month throughout the pregnancy.

• Take a pregnancy test after a few days of late period
• if the test is positive, make an appointment with a gynecologist or a midwife. The first compulsory prenatal examination (3) must take place before the end of the 1st trimester but it is advisable to consult before.
• continue vitamin B9 supplementation if prescribed during a pre-conceptual visit

• 1 month pregnant, in case of bleeding, severe pain in the lower abdomen or on one side, it is important to consult in order to rule out any suspicion of miscarriage or ectopic pregnancy.
• if this has not been done during the pre-conceptual assessment, it is advisable to perform an oral assessment in order to avoid any complications during pregnancy.
• Even if the pregnancy is not known at the start, as a precaution, risky practices should be avoided: consumption of alcohol, drugs, tobacco, exposure to X-rays, taking medication. This is all the more important that at the stage of organogenesis, the embryo is very sensitive to teratogenic agents (substances which can cause malformations).

This is because alcohol consumption during pregnancy can lead to fetal alcohol syndrome which can disrupt the growth of the 1-month-old embryo. This syndrome leads to malformations, developmental disorders at the neurological level and growth retardation. The baby is more likely to be born prematurely. Tobacco is bad for everyone and even more so for the pregnant woman even 1 month and the fetus. Before you get pregnant, smoking decreases fertility. During the first month of pregnancy, smoking increases the risk of miscarriage and premature birth. In addition, cigarettes should be banned throughout these 9 months, but in particular for the 1 month old fetus. It compromises its good in-utero development. The future baby can be born with deformities. In addition, smoking during pregnancy increases the risk of breathing problems in the baby after birth. 

Regarding taking medication during this 1st month of pregnancy, it should only be done on medical advice. Pregnant women should not self-medicate. Natural and safe remedies exist to relieve pregnancy ailments. Many drugs have unwanted effects and consequences for the development of the 1-month-old embryo, because it does not have the capacity to evacuate them. It is very important to ensure that you take medication, especially if you are pregnant.