The weight of the mother before conception, her diet during pregnancy have an impact on the proper development and health of the fetus.
The ideal weight to start a pregnancy is provided by the body mass index (BMI) which is calculated as follows:
BMI = Weight (in kg) / Height^2 (in m). The optimal BMI for conceiving is between 23 and 24 kg/m^2. Thus, for a woman measuring 1.65 m, the ideal weight based on BMI would be between 62.60 kg and 65.30 kg. With a BMI of 19 (which is 51.70 kg for 1.65 m), fertility drops to 25%!
The parallel study of mothers' BMI before conception and the monitoring of their pregnancy shows that the frequency of complications during pregnancy and childbirth is greater when the difference in the mother's BMI compared to the recommended norm is significant. The rate of hypotrophy is 6% in women with a BMI between 19 and 25 kg/m^2 and increases to 18% when this index is below 19. However, this relationship between the mother's pre-conception weight and the newborn's weight is subject to adjustment depending on the quality of maternal nutrition during pregnancy. Thus, a woman with a starting BMI below 19 kg/m^2 may, through high calorie and nutritional intake, have a perfectly healthy child. Moreover, a woman with a normal BMI at the time of conception, but who observes a low-calorie diet during pregnancy, significantly increases the risk of having a low-weight child. Conversely, when a woman desiring pregnancy is overweight, it is preferable for her to lose weight before becoming pregnant rather than following a low-calorie diet during her pregnancy. Indeed, her diet may be deficient in vitamins and minerals essential for her baby's development.
The nutritional needs of the fetus:
Fats
In order for the fetus's micronutrient needs to be met, the barrier between the uterus and the placenta must be as efficient as possible. To achieve this, it is necessary to increase consumption of omega-3 fatty acids and reduce intake of saturated fats and trans fatty acids. It should be recalled that omega-3 fatty acids are essential for the proper development of the child's brain and retina.
Sugars
The brain, which represents 2 to 3% of the child's total weight, consumes 20 to 30% of the total energy. It obtains this from glucose circulating in the blood and is very sensitive to any variation. As it also has only a very small reserve of glycogen (the body's sugar reserve form), it is essential for any future mother to ensure regular intake of complex carbohydrates (i.e., at every meal, slightly more in the evening to facilitate sleep).
Proteins
When a pregnant woman is deficient in proteins, insulin production is disrupted, as is sugar digestion which depends on it. This deficiency is thought to be the cause of certain cases of gestational diabetes, a condition often serious for the fetus: increased risk of malformations and death at birth, then of overweight and glucose intolerance during childhood and adolescence.
Neither too small nor too large
The period preceding conception is essential in the life of the future child. Indeed, by adopting good lifestyle habits and balancing her weight before conception and throughout pregnancy, the future mother creates a favorable environment for the proper development of the fetus. This balance significantly reduces the risk of giving birth to a hypotrophic (low weight) or overweight baby.
Low birth weight (or hypotrophy) has multiple immediate consequences: increased morbidity and mortality during the perinatal period and early childhood. This risk is multiplied by a factor of 3 to 10 when birth weight is between 2.5 and 1.5 kg, and by 10 to 50 below 1.5 kg. This problem of hypotrophy is particularly relevant for women who have been treated for infertility. These cases of infertility are mostly treated by prescribing an ovulation inducer or by in vitro fertilization, without prior correction of the often necessary weight adjustment: in general, these women are rather thin. The risk of hypotrophy is further increased by these techniques exposing to multiple pregnancies. Therefore, nutritional treatment should precede infertility treatment. Hypotrophy also has medium and long-term consequences, less well known, but equally formidable. Affected children are more often prone to certain conditions such as asthma and schizophrenia. In adulthood, they more often suffer from overweight and the induced complications (fatty diabetes, hypercholesterolemia, hypertension, myocardial infarction, stroke). Finally, hypotrophic girls at birth face an additional risk, that of giving birth to low birth weight babies themselves.
Newborn overweight. Generally related to the mother's overweight before conception, it is responsible either for delays in the onset or difficulties during childbirth, or for distress and trauma for the baby. These events themselves are the cause of increased risks of cesarean section, hospitalization, and neonatal mortality. Finally, newborn overweight is a precursor to childhood obesity and its multiple complications.