Objectives To assess physical fitness in pregnancy and to evaluate its effect on perceived health, back pain, blood pressure and duration of gestation. Also, to evaluate the effect of serum relaxin levels on blood pressure and duration of gestation. Material and methods A prospective cohort of 520 pregnant women were examined in early pregnancy and five months postpartum with regard to socio-demographic characteristics and estimated peak oxygen uptake (V̇O2 peak, est.). Serum concentrations of relaxin were carried out in early pregnancy. Physical exercise, possible back pain and blood pressure were measured repeatedly throughout pregnancy. Results Absolute V̇O2 peak, est. in early pregnancy was positively correlated to perceived health, which was lower during than after pregnancy. The average absolute V̇O2 peak, est. in early pregnancy of 2.4 l/minute was 0.02 l/minute less than the V̇O2 peak, est. postpartum, while regular physical exercise decreased throughout pregnancy. Absolute V̇O2 peak, est. in early pregnancy was not associated to the incidence of any low back pain location in pregnancy or postpartum, but inversely to intensity of back pain and diastolic blood pressure and positively with duration of gestation. Elevated serum relaxin levels were associated with decreased diastolic blood pressure and higher duration of gestation among women with miscarriage. Conclusions Perceived health, diastolic blood pressure and duration of gestation were positively affected by physical fitness while no effect was shown on the incidence of back pain. The effect of physical fitness on duration of gestation and diastolic blood pressure might have clinical implications as well as the increased serum relaxin levels on miscarriages.

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Preterm birth (PTB), defined as birth before 37 weeks of gestation, is the leading cause of neonatal morbidity, and survivors can face lifelong medical difficulties. PTB remains a clinical challenge worldwide, with rates of PTB rising in all countries with reliable data. A lack in understanding of the mechanisms that lead to PTB has made developing diagnostics and therapeutics challenging, and existing ones are often ineffective. For a successful pregnancy, the major reproductive organs and surrounding tissues must sustain the growing loads of pregnancy. The cervix is one of these major reproductive organs. The cervix sits at the base of the uterus and has a versatile mechanical function in pregnancy. First, it must stay closed during gestation while the fetus develops; second, the cervix must remodel sufficiently and timely to dilate and allow delivery. The proper timing and extent of remodeling are critical for a healthy pregnancy. Improper cervical remodeling is a final common pathway to PTB and is the tissue of focus in this thesis. To improve our ability to identify when a PTB birth will occur and ultimately be able to treat those at risk, this thesis will identify the mechanical role of three extracellular matrix (ECM) components at various gestational ages and evaluate the ability of two major hormones to alter cervix function. Using experimental techniques (large-deformation tensile testing, digital-image correlation, imaging, biochemical) and theoretical and computational techniques (constitutive modeling, finite element analysis), the mechanical behavior of whole mouse cervices will be characterized in wild type, genetic knockout, and hormone-treated animals. First, the loss of both Class-I small leucine rich proteoglycans (SLRPs), decorin and biglycan, is detrimental to cervix function in late gestation. When the cervix should be most compliant and extensible, cervices without decorin and biglycan cannot stretch and are as stiff as the nonpregnant cervix. The loss of these proteoglycans also slows the cervix’s stress dissipation mechanism in late gestation, which could put the cervix at increased risk for damage. The mechanism of stiffening and lost viscoelasticity indicates the fibril crosslinking associated with SLRPs is a structural mechanism of the ECM contributing to cervical remodeling. Second, the loss of hyaluronic acid diminishes the cervix’s mechanical function at every gestational age tested. For nonpregnant to mid-gestational age, the cervix is softer than normal. Though by late gestation, the loss of hyaluronic acid stiffens the cervix; this is at a point when the cervix should be at its softest. The loss of hyaluronic acid also decreases the cervix’s protective stress dissipation mechanism in late gestation. There is limited knowledge of the interaction of collagen, elastic fibers, and hyaluronic acid in the cervix. The significant mechanical role of hyaluronic acid in the cervix warrants exploration of the structural mechanisms of these functional changes. Third, the loss of endogenous hormones stiffens the tissue and increases extensibility compared to the nonpregnant cervix. The administration of estrogen recovers large amounts of extensibility (beyond the stretch level of a late gestation cervix), stiffens the tissue (such that it is stiffer than a nonpregnant cervix), and recovers a significant amount of cervix strength. Fourth, relaxin increases cervix extensibility in mid-gestation and endows the cervix with viscoelastic ability in late gestation. Altogether, understanding the correlation between these extracellular matrix components, hormones, and functional changes of the cervix is fundamental to teasing out mechanisms of cervical remodeling and developing improved PTB diagnostics and therapeutics.

No description available.