The mother: Adaptation to pregnancy and normal metabolism

Adaptation to pregnancy and normal metabolism

Francesca Parisi, Alice Zavatta, Roberta Milazzo, and Irene Cetin

Introduction

During pregnancy, several maternal anatomical and physiological changes occur in order to ensure proper development of the growing fetus and to prepare the mother for labor and delivery. In this context, maternal adaptation to pregnancy includes numerous cardiovascular, renal, hematologic, respiratory, and metabolic changes that finally lead to increased oxygen and nutrient supply to the fetoplacental unit and to enhanced protection against postpartum hemorrhage for the mother. Table 1.1 summarizes the main mechanisms of maternal adaptation to pregnancy with a systems approach.

Table 1.1 Maternal adaptation to pregnancy
System	Increase	Decrease
Cardiovascular	Heart rate	Systemic vascular resistance
	Blood volume	Systemic blood pressure
	Cardiac output	Blood viscosity (Hct and Hb)
	Venous stasis
Hematologic	Plasma volume	Protein S activity
	Red blood cell mass	Prothrombin time (slightly)
	Fibrinogen, factors II, VII, VIII, X, XII, XIII	Hemoglobin concentration
	Thrombin activatable fibrinolytic inhibitor, PAI-1, PAI-2	Platelet count (slightly)
	D-dimer
	Resistance to activated protein C
Renal	Organ volume	Creatinine
	Renal blood flow	Natremia
	GFR
	Urinary frequency and nocturia
	Dilatation of the ureters and renal pelvis
	Proteinuria and glucosuria
	Excretion of HCO3−
Respiratory	Minute ventilation	Functional residual capacity
	PO2	PCO2
	Slight alkalosis
	Oxygen consumption
Gastrointestinal	Gastroesophageal reflux	Intestinal peristalsis
	Lithogenicity of bile	Gallbladder motility
	Serum alkaline phosphatase	Serum level of AST, ALT, γ-GT
		Albumin concentration
Metabolism	Insulin resistance	Starving glycemia
	Postprandial glycemia
	FFA concentration
	Cholesterol and triglyceride concentrations
Immunity	Leukocytes count	Leukocytes function
	Th2 response	Th1 response
	CRP and ESR	Immunoglobulin titles
Abbreviations: CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; FFA, free fatty acid; Hb, hemoglobin; Hct, hematocrit; GFR, glomerular filtration rate; PAI, plasminogen activator inhibitor; PCO2, partial pressure of carbon dioxide; PO2, partial pressure of oxygen; Th, T-helper lymphocytes.

Moreover, an evolutionary revolution occurred over the last decades: the intrauterine period of development has been shown to permanently shape the adult life, mainly through epigenetic modifications that affect the postnatal phenotype of the offspring in later life (1). This concept has given a new pivotal role to obstetric care also for improving the health status and the risk of chronic disease of future generations. In this context, maternal maladaptation to pregnancy may lead to short-term derangements in intrauterine development, with abnormal fetal growth, birth weight, and morphological development, and may finally shape the risk of chronic diseases of the child and the adult as a long-term effect.

Periconceptional period

Despite the great attention given to the second half of pregnancy, the research focus has recently moved to the first trimester and the time around conception (the “periconceptional period”) in order to grant early screening and diagnosis of subsequent adverse pregnancy outcomes with long-term health effects (Figure 1.1). The periconceptional period represents a chaotic time window from a biological point of view, starting with gamete maturation, going through the events of fertilization and implantation, and ending with the development of the embryonic structures and the first stages of placentation. This period is crucial for a normal adaptation to pregnancy, and any pathological deviation in this time window may finally lead to overt diseases in the second half of pregnancy and to larger shifts in the adult phenotype than the second half of pregnancy. In fact, if it is true that perinatal morbidity and mortality and the risk of noncommunicable diseases are mainly related to complications diagnosed during the second part of pregnancy (e.g., hypertensive disorders, intrauterine growth restriction, preterm birth), it is also evident that these conditions originate during the very first stages of pregnancy and even before, thus involving the most important stages of gamete, placenta, and embryo development (2).