There are many contradictions regarding the way in which the dentist should approach the emergency treatment and the other treatments that occurred in the oral cavity in women in the first trimester of pregnancy. Some authors consider that such treatments can be conducted without any risk to the embryo. On the other hand, geneticists point out that this period is of maximum sensitivity for the embryo if exposed to teratogenic factors that can cause irreversible changes. Hence the importance of proper dental treatment in female patients in the first trimester of pregnancy.
Key words: pregnancy, embryogenesis, teratogenic factors, treatment approach
The birth of a healthy child is the wish of any parents. This is only possible through good pregnancy management both in the first trimester and throughout the entire pregnancy.
The prenatal diagnosis allows the early detection of congenital anomalies representing a complex medical activity, in which the geneticist and the obstetrician have an essential role in evaluation, diagnosis and genetic counseling. The methods of genetic screening conducted during pregnancy, distributed differently in the three trimesters, accurately highlight the time when different teratogenic factors occurred.
Given that during pregnancy there may be conditions that require emergency dental treatment, the dentist has the task, but also the responsibility to establish and carry out the treatment to take all the necessary measures in order not to change the normal course of pregnancy.
Embryonic stage (1st trimester)
The first three months of pregnancy represent the embryonic stage in which the differentiation of tissues and organs takes place. In this phase the embryonic leaves from which the organs will develop appear. In the first week, the egg cell segmentation takes place, representing the starting point for all the structures to be differentiated and developed. The zygote comprises all the genetic material from the two parents transmitted through the two gametic cells. After the segmentation of the zygote, a process of cell proliferation takes place, in which the first two blastomeres appear at about 25-30 hours, the other 4 blastomers at 48 hours and then another 8 blastomers at 72 hours. 
Next is the morula stage characterized by 12-14 blastomeres. While the morula is formed within the first three days, the conception product advances to the uterus, stays free for approximately 72 hours in the uterine cavity, after which the uterine fluid crosses the pellucid area and enters the blastomeres of the morula dislocating them. The cells located at the periphery of the egg are the trophoblast which differentiates into a deep layer, called cytotrophoblast, and a peripheral layer, called syncytiotrophoblast, with role in implantation in the early stages of placenta and in the onset of uteroplacental circulation. Thus, the first two embryonic attachments appear: the yolk sac and the primary amniotic cavity. In the second week of development (12-14) the process of gastrulation begins, through which the cells of the blastocyst migrate and finally form the trilaminar embryo with the three definitive germinal layers: the ectoderm, the endoderm and the mesoderm.
Inside the embryo button, there is a space that separates the amnios from the embryonic cells that remain and form the embryonic disc.
From the deep cells of the embryonic disc, the endoderm is separated in the form of flat cells, while inside the embryonic button there is a space that separates the amnios from the embryonic cells from which the embryonic disk is formed.
Through the thickening of the endoblast, between the ectoblast and the endoblast, a third mesodermal leaf is formed – the mesodermic one that will eventually spread throughout the embryonic disc interspersed between the ectoblast and the endoblast, which will remain joined in only two areas.
The three-dimensional embryonic disc, by bending, will form the body of the future fetus. Through complete differentiation, the embryo layers will form, in the process of embryogenesis, between the fourth and fifth week, to the different organs and tissues that will make up the body.
From the ectoderm derives: the nervous system, the sensory apparatus, the eyes, the ears, the endocrine glands, the epidermis and the appendages, the tooth enamel, the connective membrane of the eye with the tear glands and the lens.
From the mesoderm derives: the osteo-articular system, the muscular, circulatory system, the genital-urinary tract, the cortical-adrenal glands, the gonads without sex cells, the genital tracts, the connective tissue of the dermis and the hypodermis, the blood vessels, the blood and the hematogenous tissue, the connective stroma of various organs.
From the endoderm derives: the digestive and respiratory tract, the epithelium of the middle ear, the epithelium of the bladder, the epithelium of the female urethra, the epithelium of the prostatic urethra, the epithelium of the inferior part of the vagina, the sex cells. 
The first two weeks after conception are generally slightly harmful to the embryo, which has a high resistance to teratogenic agents, the repair possibilities being very high. The embryo is very sensitive to the teratogenic effect between the third and tenth week after conception. Most times, the diagnosis of pregnancy is beyond this period, so it is mandatory for the dentist to discuss with the patient about the teratogenic potential of the prescribed medication during this fertile period. 
Teratogenic factors are grouped into three broad classes: genetic factors, ecological factors and the interaction between genetic predisposition and the action of external factors.
I – Genetic factors:
a) accidents in the genesis of the parents’ gamets;
b) the genetic constitution of the embryo;
c) changes in the genetic apparatus of the conception product that occurred during the early stages of embryogenesis. 
II – Ecological factors:
1. Physical factors:
- ionizing radiation
- electromagnetic radiation
- photonic radiation (X and Y)
Irradiation can be external and internal. External through partial or total exposure of the body to external radiation, internal through the penetration into the body of radiation by inhalation, ingestion or parenteral administration (for diagnostic or therapeutic purpose). Doses higher than 200 rays (radon) are harmful during the embryonic period.
b) thermal energy:
- febrile conditions (hyperthermia and hypoxia)
- prolonged exposure to high ambient temperatures.
c) mechanical factors:
- congenital dislocation of the hip;
- the equinovarus
- arthrogryposis 
2. Chemical and medicamentary factors:
- increase of the chemical pollution of the environment (dioxin, poisoning with high doses of lead, etc.)
- therapeutic drugs: cytotoxic (aminopterin, methotrexate, folic acid antagonists)
- hormones: estrogens in high doses, androgens given at the beginning of pregnancy, progesterone, estroprogestative contraceptives
- anticoagulants and antivitamins K
- antibiotics. Pregnant women should avoid them (tetracycline, streptomycin, kanamycin and gentamicin).
- anti-inflammatory drugs (indomethacin)
- anticonvulsants (oxazolidine, hydantoin, phenytoin, phenobarbital)
- synthetic compounds of vitamin A (isotretinoil, etretinate)
- cyclooxygenase inhibitors (aspirin and ibuprofen)
- hallucinogenic substances (cocaine, opium, marijuana, LSD, cannabis)
- alcohol, tobacco and, coffee .
3. Biological factors
- viruses (rubella, herpes, shingles)
- bacteria (lues, microplasma)
- parasites (toxoplasmosis)
4. Maternal factors
- the age of the mother
- the physiological condition of the mother.
Dental approach in the first trimester of pregnancy
The dentist must prepare the medical record (an act of forensic importance) even if the patient only requests emergency treatment (abscess, acute apical periodontitis, pulpitis, etc.).
The medical record must include:
- personal data
- the age of the mother
- workplace (toxic environment, if any)
- stage and type of pregnancy (natural or implanted)
- the registration by the obstetrician
- making the Bi Test (ultrasound measurement of the nuchal translucency and determination of plasma protein A)
- the presence of a virus or other infectious process during this period, as well as the curative treatment, if any
- the presence of other teratogenic factors: smoking, consumption of alcohol or coffee
- current or past drug use
- the presence of a chronic condition that requires medication.
The record will also include:
- all treatments conducted by the dentist and the prescribed medication
- anesthesia given in case of need (without adrenaline and in small doses)
- prescribing antibiotics (only if the situation requires it).
Recommendation for X-rays should be avoided.
In the first trimester of pregnancy, it is recommended to delay non-emergency treatments.
The medical record, accurately filled in, with the patient’s informed consent, is the evidence of the dentist that they are not involved in any way in the loss of pregnancy or the birth of a child with malformations.
Considering, on the one hand, that the placenta is a semi-permeable membrane of a lipoprotein nature, easily crossed by all chemical compounds in the environment or by drugs that have a molecular mass below 600 daltons (the dalton is the unit of atomic mass almost equal to the mass of a hydrogen atom), and on the other hand that the multitude of teratogenic factors can adversely influence the embryo in the first three months of pregnancy, the dentist must carefully approach and decide upon the problems of patients in this situation who require specialized treatment.
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