**5.1. Preterm delivery**

**4. Physiological homeostasis changes that may affect elderly** 

ficiency, increasing morbidity and mortality for both the mother and the baby.

Modifications in the respiratory system also take place during pregnancy. Pulmonary function is affected by location and orientation changes of the airway and configuration of the thorax due to the presence of the gravid uterus as well as hormonal effects. The elevation of the diaphragm decreases the lung's vertical diameter and subsequently enlarges the transversal and anteroposterior diameters. The displacement of the diaphragm produces a progressive decline in expiratory reserve volume and residual volume. Progesterone, cortisol, and relaxin produce dilatation of the airway in pregnant women reducing pulmonary resistance [37]. Ageing is associated with structural changes not only in the chest bones and diaphragm but also in the lung tissue. The dilatation of the alveoli decreases the exchange surface increasing the residual volume and functional residual capacity. These physiological changes added to those typical from pregnancy can cause alterations in the ventilation-perfusion ratio in elderly

Dilatation of the renal pelvis and ureters is characteristic during pregnancy on account of the growth of the uterus and the effect of hormones, such as progesterone, that cause relaxation of the smooth muscle. This predisposes women to suffer from urinary tract infections during pregnancy. Renal function is also modified during this period with an increased blood flow and glomerular filtration up to 60% [38]. Precisely for that reason, we should be aware of any medical pre-existing renal dysfunction that can worsen during pregnancy. For example,

which appear more frequently in women of advanced age.

During pregnancy, a series of physiological homeostatic changes take place in a woman's body that activate numerous adaptive mechanisms, mainly cardiovascular, respiratory, and hemodynamic. These changes are essential for the evolution and progress of a normal pregnancy. Adaptive mechanisms can be compromised as a consequence of underlying diseases,

The increase in cardiac output, extracellular volume, and arterial compliance and the decrease in arterial blood pressure (BP) and peripheral resistance are some of the cardiovascular changes that occur in pregnant mothers [33]. Mean BP decreases during pregnancy presenting its lower values in the middle of the second trimester and then it starts to increase reaching values comparable to non-pregnant women at the end of pregnancy. In addition, redistribution of blood flow to different organs is essential in order to cover for the higher metabolic requirements, and so venous return and cardiac output raise dramatically [34]. There are also hormonal factors that favour these changes to appear. Oestrogens and relaxin are both involved in the production of nitrous oxide (NO), which produces vasodilatation during pregnancy and facilitates the distribution of blood to key organs [35, 36]. Ageing is associated with structural changes in the vascular wall, which leads to loss of arterial elasticity and reduced arterial compliance. Cardiovascular adaptive mechanisms could be impaired in elderly mothers due to pre-existing hypertensive disorders or venous insufficiency; therefore, they are at high risk of suffering from complications such as preeclampsia and placental insuf-

**mothers' health**

104 Multiple Pregnancy - New Challenges

mothers.

We defined preterm delivery as birth prior to 37 weeks of gestation. Preterm birth complicates 5–18% of pregnancies and is the leading cause of neonatal death and the second cause of childhood death below the age of 5 years [43]. We should distinguish between preterm deliveries medically indicated secondary to foetal or maternal complications during pregnancy, such as preeclampsia, intrauterine growth restriction, or gestational diabetes, from those that occur after spontaneous onset of labour. Many studies have described multiple risk factors for preterm birth [44–47], although others propose this entity is a syndrome caused by multiple pathologic processes [43].

Twin pregnancy has been classically described as one of the risk factors associated with preterm birth. Although multiple gestation accounts for only 2–3% of all births, this type of gestation constitute 17% of births before 37 weeks of gestation and 23% of birth before 32 weeks [48]. The mechanism for preterm birth in multiple gestations may be related to the increased uterine distension; however, some studies suggest that the increased amount of oestrogen, progesterone, and sex steroids compared with singleton pregnancies could play an important role in the physiopathology of the syndrome [49, 50].

or older, pregnancy interval of more than 10 years, BMI of 35 kg/m2

**5.3. Gestational diabetes**

immaturity that may cause foetal neonatal distress.

when GDM or glucose intolerance is present [73].

(body mass index over 30 kg/m2

sequences for the future health of both the mother and the baby.

family history of preeclampsia), should receive a daily aspirin dose [63].

tance of achieving a singleton gestation to avoid adverse perinatal outcomes.

As we have seen before, single-embryo transfer is the main technique to reduce the rate of twin pregnancies. We should focus our effort on identifying those women with pre-existing medical conditions who are predisposed to suffer PE and, if applying ART, enforce the impor-

Gestational diabetes mellitus (GDM) is a diabetic state diagnosed for the first time in pregnancy. It is one of the most common metabolic disorders in pregnancy. GDM complicates 3–5% of pregnancies and it is considered a risk factor for adverse perinatal outcomes, such as macrosomia, shoulder dystocia, cerebral palsy, and foetal death [64–66]. It is defined as basal glucose ≥126 mg/dl (7.0 mmol/l), HbA1c ≥ 6.5% (47.5 mmol/mol), or glucose levels ≥200 mg/dl (11.1 mmol/l) at any time of the day or screen positive for any of the GDM tests available [67].

Diabetes predisposes pregnant women to suffer urine infections, hypertensive disorders, and prematurity. It is well known that pregestational diabetes can cause foetal malformations, intrauterine growth restriction, stillbirth, and congenital heart disease probably due to vascular alterations in mothers. Both gestational and pregestational diabetes have effects on the foetus secondary to hyperinsulinemia, such as macrosomia, polyhydramnios, and foetal lung

Women of advanced maternal age are at a higher risk of developing GDM [68]. Twin pregnancies have also been related to GDM [69]. The development of GDM usually indicates a reduced pancreatic reserve in the pregnant mother and is a marker of pre-diabetes, putting them at a higher risk of developing diabetes mellitus type 2 in the future. It is essential to highlight the importance of adopting healthy habits during pregnancy in order to avoid con-

Gestational diabetes in twins is also associated with an increased risk of hypertensive disorders, macrosomia, and preterm birth, but it reduces the risk for low birth weight [70]. Furthermore, it has been suggested that gestational diabetes could potentially benefit twin pregnancies, as low 5-min Apgar score and neonatal death are reduced in twins compared to singletons when this maternal complication is present, maybe due to the increased birth weight of the twin pairs [71, 72]. However, growth in the twin pair tends to be asymmetric

Early diagnosis and treatment are essential in order to avoid complications during pregnancy. Nowadays, guidelines from different countries recommend the screening for gestational diabetes in women with risk factors such as previous history of gestational diabetes, obesity

of them support the use of a universal screening test in the second trimester and also in the first trimester in every woman over the age of 35 [77]. However, the increase in maternal age over the last years implies offering this diagnostic test to a very high percentage of the

), and previous delivery of a macrosomic baby [74–76]. Some

or more at first visit, or

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Multiple Pregnancy in Women of Advanced Reproductive Age

http://dx.doi.org/10.5772/intechopen.81096

The effect of maternal age also influences the risk of preterm birth. Some studies suggest that even after adjusting for cofounders such as hypertension, diabetes, race, and mode of conception, maternal age over 40 years is an independent risk factor for preterm delivery [47, 51].

The widespread availability of reproductive technology has increased the percentage of multiple gestations and preterm delivery as an aftermath. Therefore, it is our duty to inform women of the risk of this type of pregnancies and enforce the use of the different strategies in order to achieve singleton pregnancy.
