Age does not affect uterine resistance to vascular flow in patients undergoing oocyte donation

A mathematical model of vascular and hemodynamics changes in early and late forms of preeclampsia

Preeclampsia-eclampsia syndrome is a leading cause of maternal mortality. The precise etiology of preeclampsia is still not well-defined and different forms exist, including early and late forms or preeclampsia, which may arise via distinctly different mechanisms. Low-dose aspirin administered at the end of the first trimester in women identified as high risk has been shown to reduce the incidence of early, but not late, preeclampsia; however, current risk factors show only fair predictive capability. There is a pressing need to develop accurate descriptions for the different forms of preeclampsia. This paper presents 1D fluid, solid, growth, and remodeling models for pregnancies complicated with early and late forms of preeclampsia. Simulations affirm a broad set of literature results that early forms of preeclampsia are characterized by elevated uterine artery pulsatility index (UA-PI) and total peripheral resistance (TPR) and lower cardiac output (CO), with modestly increased mean arterial blood pressure (MAP) in the first half of pregnancy, with elevation of TPR and MAP beginning at 20 weeks. Conversely, late forms of preeclampsia are characterized by only slightly elevated UA-PI and normal pre-term TPR, and slightly elevated MAP and CO throughout pregnancy, with increased TPR and MAP beginning after 34 weeks. Results suggest that preexisting arterial stiffness may be elevated in women that develop both early forms and late forms of preeclampsia; however, data that verify these results are lacking in the literature. Pulse wave velocity increases in early- and late-preeclampsia, coincident with increases in blood pressure; however, these increases are mainly due to the strain-stiffening response of larger arteries, rather than arterial remodeling-derived changes in material properties. These simulations affirm that early forms of preeclampsia may be associated with abnormal placentation, whereas late forms may be more closely associated with preexisting maternal cardiovascular factors; simulations also highlight several critical gaps in available data.

A mathematical model of maternal vascular growth and remodeling and changes in maternal hemodynamics in uncomplicated pregnancy

The maternal vasculature undergoes tremendous growth and remodeling (G&R) that enables a > 15-fold increase in blood flow through the uterine vasculature from conception to term. Hemodynamic metrics (e.g., uterine artery pulsatility index, UA-PI) are useful for the prognosis of pregnancy complications; however, improved characterization of the maternal hemodynamics is necessary to improve prognosis. The goal of this paper is to develop a mathematical framework to characterize maternal vascular G&R and hemodynamics in uncomplicated human pregnancies. A validated 1D model of the human vascular tree from the literature was adapted and inlet blood flow waveforms at the ascending aorta at 4 week increments from 0 to 40 weeks of gestation were prescribed. Peripheral resistances of each terminal vessel were adjusted to achieve target flow rates and mean arterial pressure at each gestational age. Vessel growth was governed by wall shear stress (and axial lengthening in uterine vessels), and changes in vessel distensibility were related to vessel growth. Uterine artery velocity waveforms generated from this model closely resembled ultrasound results from the literature. The literature UA-PI values changed significantly across gestation, increasing in the first month of gestation, then dramatically decreasing from 4 to 20 weeks. Our results captured well the time-course of vessel geometry, material properties, and UA-PI. This 1D fluid-G&R model captured the salient hemodynamic features across a broad range of clinical reports and across gestation for uncomplicated human pregnancy. While results capture available data well, this study highlights significant gaps in available data required to better understand vascular remodeling in pregnancy.

Male age negatively impacts embryo development and reproductive outcome in donor oocyte assisted reproductive technology cycles

OBJECTIVE

To determine whether male age influences embryo development and reproductive potential in assisted reproductive technology cycles.

DESIGN

Retrospective cohort analysis.

SETTING

Private IVF center.

PATIENT(S)

One thousand twenty-three male partners participating in anonymous oocyte donation cycles.

INTERVENTION(S)

Infertile couples undergoing 1,023 anonymous oocyte donation cycles.

MAIN OUTCOME MEASURE(S)

Live birth rate.

RESULT(S)

A significant increase in pregnancy loss, decrease in live birth rate, and decrease in blastocyst formation rate were noted in men >50 years of age. There was no significant difference in implantation rate, pregnancy rate, or early embryo development through the cleavage stage (demonstrated by fertilization rate, embryo cleavage rate, percentage of nonfertilized or polyspermic embryos, rate of embryo arrest, or seven or more cell embryo development on day 3). Men < or =45 years of age had significantly more semen volume and more motile sperm than men >45 years of age. There was no significant change in sperm morphology or concentration.

CONCLUSION(S)

After controlling for female age with use of the donor oocyte model, male age >50 years significantly affected pregnancy outcomes and blastocyst formation rates. Semen volume and total motility decreased with increasing male age. Initial embryo morphology through the cleavage stage was not affected.

The "vanishing embryo" phenomenon in an oocyte donation programme

BACKGROUND

We studied the incidence of vanishing embryos (VE) in pregnancies achieved by oocyte donation and evaluated the obstetric and perinatal complications.

METHOD

A retrospective study was carried out based on a chart review of 399 patients with multiple pregnancies from our oocyte donation programme. We defined vanishing phenomenon as the early resorption, in the first trimester, of one or more embryos in a multiple gestation, after confirming embryonic heart activity by transvaginal ultrasound.

RESULTS

Vanishing embryo was observed in 75 patients (18.8%). In 60 patients (80%) this phenomenon occurred before the ninth gestational week. A higher incidence of VE was observed in patients who initially showed a higher number of gestational sacs (P < 0.03). Vaginal bleeding in the first trimester was significantly higher in patients with VE (P < 0.005). Miscarriage rate was similar in pregnancies with and without VE (P = NS). The incidence of pregnancy induced hypertension was decreased in the group with VE (P < 0.03). Preterm spontaneous rupture of membranes occurred more frequently in pregnancies with VE (P < 0.05). However, gestational age at delivery was similar in the group with VE and the controls.

CONCLUSIONS

The high incidence of VE in pregnancies achieved by oocyte donation should be considered when counselling patients with high order multiple gestations.

Prediction of pregnancy rate of in vitro fertilization and embryo transfer in women aged 40 and over with basal uterine artery pulsatility index

PURPOSE

The purpose was to determine the effect of basal uterine perfusion on the pregnancy rates of in vitro fertilization and embryo transfer (IVF-ET) in women aged 40 and above.

METHODS

A total of 47 patient aged 40 and over underwent IVF-ET. The conception cycles and the nonconception cycles were compared.

RESULTS

Of the 47 patients, 4 patients were pregnant (8.5%). The mean age, basal follicle stimulating hormone (FSH), basal estradiol (E2) level, antral follicle count (AFC), number of ampoules of gonadotropin used, E2 levels and endometrial thickness on the day of human chorionic gonadotropin (hCG) administration, number of retrieved and fertilized oocytes, and number of transferred embryos were not statistically significant between the conception and nonconception cycles. However, the basal uterine artery pulsatility index (UA PI) was significantly lower in the conception cycles (P < 0.001). The receiver operating characteristics (ROC) curve analysis for basal FSH, AFC, and basal UA PI in predicting the pregnancy rate of IVF in patients aged > or = 40 were demonstrated. The best prediction rate was achieved by a pulsatility index cutoff of < 2.0 for a receptive uterus.

CONCLUSIONS

Increased uterine perfusion in the early follicular phase enhanced the pregnancy rate of IVF in women aged 40 and above. It is therefore essential that patients aged > or = 40 with poor basal uterine perfusion should be identified early in the early follicular phase of the menstrual cycle to apply appropriate intervention to improve the uterine circulation for the subsequent chance of pregnancy.

Ovarian follicular dynamics: from basic science to clinical practice

The management of low responders (LR) to ovarian stimulation in cycles of assisted reproduction (AR) is a difficult challenge. Aging of the ovary and LR are coincidental in many situations, but LR is also present in young patients undergoing AR. In fact, today it is a recognized cause of infertility. When the aged ovary is considered, there is evidence that the functioning of the granulosa cells as well as the quality of the oocytes and resulting embryos are affected. Similarly, in young LR, the production of inhibin is affected. However, there is no evidence that the quality of the oocyte and/or the resulting embryo is affected. In this study, we have retrospectively analyzed our files and observed that the quality of the oocytes and embryos was similar between younger and older LR and normal responders (NR). Studies using color Doppler vaginal ultrasound have shown that the pulsatility index (PI) and the resistance index (RI) were increased in LR as compared with NR, suggesting that there was some degree of vascular resistance to flow. Treatment of LR is also a difficult challenge. Ovum donation is a successful treatment for LR, since cumulative birth rates are > 85% with four attempts of embryo transfer. The future may be promising for LR once new technologies are introduced into clinical practice. The use of recombinant gonadotropins and genetically engineered human gonadotropin derivatives may be of considerable help for LR. Similarly, non-gonadotropin hormones, such as cytokines or growth factors, may be shown to play a role in the stimulation of the ovary in the near future, and may therefore open new frontiers for treatment of LR.

Evidence of interplay between plasma endothelin-1 and 17 beta-estradiol in regulation of uterine blood flow and endometrial growth in infertile women

OBJECTIVE

To determine the effects of gonadotropin-induced ovarian stimulation on the plasma levels of endothelin-1 as well as on uterine blood flow and endometrial thickness.

DESIGN

Controlled cross-over clinical study.

SETTING

Academic research environment.

PATIENT(S)

Eighteen volunteer infertile women (31.4 +/- 2.5 years, mean +/- SE) participating in an IVF-ET program.

INTERVENTION(S)

Transvaginal Doppler ultrasound was performed and blood samples were collected 4 days after the LH surge in a spontaneous cycle and 4 days after hCG administration in a subsequent gonadotropin-stimulated cycle.

MAIN OUTCOME MEASURE(S)

Plasma levels of E2, P, and endothelin-1; uterine artery pulsatility index; and endometrial thickness.

RESULT(S)

Stimulated cycles were associated with significantly higher E2 levels (101.0 +/- 10.2 versus 723.5 +/- 57.3 pg/mL [conversion Factor to SI unit, 3.671]; spontaneous versus stimulated), thicker endometrium (9.2 +/- 2.5 versus 11.4 +/- 2.9 mm), and lower endothelin-1 levels (2.5 +/- 0.1 versus 2.1 +/- 0.1 pg/mL [conversion factor to SI unit, 0.4]) and pulsatility index (3.22 +/- 0.12 versus 2.63 +/- 0.08) than spontaneous cycles. Endothelin-1 correlated negatively with E2 (r = -0.38), but not with P or pulsatility index. Differences in endothelin-1 and endometrial thickness between spontaneous and stimulated cycles correlated negatively (r = -0.56) with each other.

CONCLUSION

Our results suggest an inhibitory role for E2 in the release of endothelin-1, which could be a factor in the regulation of uterine and endometrial blood flow.