Pregnancy: Obstetric Medicine

Metabolism and pregnancy

During pregnancy, important changes take place in the woman’s metabolism because of foetal and placental growth.  These changes include alterations in glucose metabolism that are brought about through the action of hormones from the placenta which antagonize the action of the pregnant woman’s insulin. This brings the metabolism to the anticipated state of “relative insulin resistance” during the course of pregnancy, a condition which is compensated, however, by the woman’s own organism, in the majority of cases without any clinical effects. There are also changes in skeletal calcium metabolism as well as in thyroid hormones concentrations and TSH (thyroid stimulating hormone) on account of the involvement of the placenta.  During pregnancy, the woman’s adaptive mechanisms operate within the new metabolic environment to facilitate the transfer of energy and nutrients to the foetus, the most specialized physician to deal with this challenging hormonal environment being the endocrinologist. During pregnancy the metabolism increases and it has been calculated that the woman’s energy needs of these nine months go up to ~77,000 calories.

The importance of the intrauterine environment for the course of pregnancy and the foetus

It is well established that the nutritional, hormonal and metabolic environment of the mother during pregnancy impacts the growth and metabolic function of the fetus. Αt some stage in later life a particular metabolic disease may emerge, this being dependent upon the acquired metabolic risk factors transferred-inscripted to the foetus during pregnancy.  The disease may either be a particular manifestation of metabolic syndrome itself, e.g. PCOS, diabetes mellitus, obesity, congenital adrenal hyperplasia, or it may comprise one part of the metabolic syndrome such as hypertension, dyslipidaemia and development of insulin resistance.

Weight control in pregnancy

The weight of the mother when pregnant will determine to a large extent the degree to which the neonate will be overweight at birth as well as the appearance or not of preeclampsia (high blood pressure) and gestational diabetes  (diabetes in pregnancy). This explains why obese women of reproductive age who wish to become pregnant must first go on a diet and weight loss programme.  Weight control during pregnancy plays a vital role in the metabolic environment of both the foetus and the mother.  Since the adipose tissue (fat) of the mother directly impacts the growth and body composition of the foetus, during her pregnancy the woman needs to be monitored by a specialized endocrinologist.  On the basis of the guidelines of the American Institute of Medicine (IOM), the endocrinologist will set targets from the very start as to the limits of weight gain, in collaboration with a gynaecologist he will carry out dietary interventions if necessary and he will closely follow up the effects of these on the development of the foetus.  Clinical conditions exist whereby the weight gain of the expectant mother could be somewhat smaller than those recommended by the IOM guidelines, and this will be carefully taken into account through the close collaboration between the endocrinologist and the gynaecologist.

Diabetes and pregnancy

The anticipated increase in insulin resistance during pregnancy among women with a concealed disturbance of their glucose metabolism (which could however build up at a later date) will result in the development of gestational diabetes.  This is a state that requires monitoring as well as, in a few cases, possibly a course of treatment via diet, tablets or insulin, the situation normally having resolved by the end of pregnancy.  Research has recently shown that in some instances, the use of antidiabetic medication is indicated that will not, of course, have any impact on the mother or foetus. Even though gestational diabetes normally resolves with the end of pregnancy, those women who exhibit it have an approximately 40% risk of developing diabetes mellitus type 2 in the future and also of manifesting it again with a new pregnancy. However, in those expectant mothers who have pre-existing diabetes mellitus type 1or 2, the anticipated further increase of insulin resistance will demand intensive monitoring. Diabetes during pregnancy can impact foetal growth, causing dysfunctions in its development, intrauterine growth restriction (IUGR, or poor growth of the baby while in the womb), future malfunctioning of its pancreatic β-cells and increased rate of fat mass deposition (macrosomia).

It is therefore clear that since the development of gestational diabetes must be diagnosed in good time, the expectant mother who has a history of diabetes mellitus, a history of a previous pregnancy with gestational diabetes, a medical history of insulin resistance prior to pregnancy, as well as those who are  overweight at the start of pregnancy or who have high birth-weight babies (>4-4.5 kilos), will need from early on to consult an endocrinologist for monitoring, which will be carried out via the two-hour oral glucose tolerance test (with 75 gr glucose).  In addition, any sudden weight gain by the mother during pregnancy forms a clinical criterion for glucose testing.

Calcium disorders in pregnancy

During pregnancy, the mother’s blood calcium levels change as maternal calcium is transferred to the foetal skeleton, contributing to its development. These changes require monitoring by the endocrinologist (e.g. maternal serum calcium levels and foetal development).

Thyroid hormones and pregnancy

Disruption of thyroid hormones during pregnancy has a direct impact on the course of pregnancy (e.g. premature birth, miscarriage, low birth weight), on the development of the foetus and also on the child’s later IQ score.  During pregnancy, levels of thyroid hormones, and particularly of TSH (thyroid stimulating hormone), in the blood of a woman who is without any medical history of thyroid diseases are likely to change during the first weeks. The result is that she will require monitoring by an endocrinologist who will judge what tests are needed; he will also establish whether the disruption stems from the thyroid and, if so, will decide upon treatment. Women with a medical history of thyroiditis, solitary thyroid nodules or goitre, or with a family history of thyroid diseases, must undergo examination during the first stages of pregnancy. Women with a previous history of hypothyroidism or hyperthyroidism need to be constantly monitored by an endocrinologist throughout their pregnancy, i.e. every 4-8 weeks according to the case, since pregnancy needs multiply rapidly and hormone levels are continuously changing.  The reference range for thyroid hormones in pregnancy is very strict and is different from those that are issued by laboratories and which concern non-pregnant women.

Monitoring of pregnant women with congenital adrenal hyperplasia, primary aldosteronism, disruption of cortisol secretion, disruption of pituitary hormones and polycystic ovarian syndrome (PCOS)

Pregnant women who have endocrinological diseases involving cortisol, androgens, prolactin, aldosterone require frequent monitoring by the endocrinologist. During pregnancy, there is an increase in the levels of the abovementioned hormones and the endocrinologist will determine in which instances the elevated values constitute a risk factor for the foetus and for the continuation of gestation.  In many cases, the endocrinologist will counsel the woman from the very start of her pregnancy