Category Archives: Human Reproduction

BACKGROUND

A limitation to our ability to distinguish between developmentally competent and incompetent eggs is our still only partial knowledge of the critical features that are needed to make a good egg and when during oogenesis these specific characteristics are acquired. The main objective of this review is to summarize the results of areas of investigation that are contributing to our still inadequate understanding of the molecular aspects of making developmentally competent eggs.

METHODS

For each area discussed, a systematic search was made using PubMed. The search was without temporal limits but mainly yielded publications between 1982–1999 (23%) and 2000–2011 (77%).

RESULTS

Taking an oocyte-centred view, we describe throughout folliculogenesis: (i) the factors that regulate oocyte growth; (ii) the role of oocyte–cumulus cell dialogue; (iii) the epigenetic organization of the oocyte genome and (iv) the storage and regulation of maternal RNAs.

CONCLUSIONS

The multifaceted complex of factors involved in oocyte growth constitutes the backbone on which oocyte developmental competence is built up. Operating behind the expression of these factors is a specific epigenetic signature established during oogenesis, but our knowledge is only approximate and major efforts will be required for more accurate analyses at specific gene loci. The growing research on small silencing RNAs during oogenesis and early oocyte development is revealing these molecules’ critical role in mRNA degradation. Our next challenge will be to dissect the complex interactions among the different molecular players identified and to establish the presence of functional links among these factors.

BACKGROUND

GnRH agonist (GnRHa) triggering has been shown to significantly reduce the occurrence of ovarian hyperstimulation syndrome (OHSS) compared with hCG triggering; however, initially a poor reproductive outcome was reported after GnRHa triggering, due to an apparently uncorrectable luteal phase deficiency. Therefore, the challenge has been to rescue the luteal phase. Studies now report a luteal phase rescue, with a reproductive outcome comparable to that seen after hCG triggering.

METHODS

This narrative review is based on expert presentations and subsequent group discussions supplemented with publications from literature searches and the authors’ knowledge. Moreover, randomized controlled trials (RCTs) were identified and analysed either in fresh IVF cycles with embryo transfer (ET), oocyte donation cycles or cycles without ET; risk differences were calculated regarding pregnancy rate and OHSS rate.

RESULTS

In fresh IVF cycles with ET (9 RCTs) no OHSS was reported after GnRHa triggering [0% incidence in the GnRHa group: risk difference 5% (with 95% CI: –0.07 to 0.02)]. Importantly, the delivery rate improved significantly after modified luteal support [6% risk difference in favour of the HCG group (95% CI: –0.14 to 0.2)] when compared with initial studies with conventional luteal support [18% risk difference (95% CI: –0.36 to 0.01)]. In oocyte donation cycles (4 RCTs) the OHSS incidence is 0% [10% risk difference (95% CI: 0.02–0.40)].

CONCLUSIONS

GnRHa triggering is a valid alternative to hCG triggering, resulting in an elimination of OHSS. After modified luteal support there is now a non-significant difference of 6% in delivery rate in favour of hCG triggering.

BACKGROUND

Aspirin is believed to improve the outcome of IVF, but previous conventional meta-analyses on the subject are conflicting. Therefore, we performed a meta-analysis with individual patient data (IPD MA) of randomized clinical trials (RCTs) on the subject.

METHODS

A systematic literature search was conducted to identify RCTs assessing the effectiveness of aspirin in IVF. Authors were asked to share their original data. In a one step meta-analytic approach, the treatment effect of aspirin was estimated with odds ratios (ORs) and 95% confidence intervals (CIs) using logistic regression, based on the intention to treat principle.

RESULTS

Ten studies fulfilled the inclusion criteria. Authors of six studies provided IPD, including 1119 patients (562 placebo and 557 aspirin). There were 160 clinical pregnancies in the aspirin (28.8%) and 179 (31.9%) in the placebo group [OR 0.86, 95% CI (0.69–1.1)]. There were 129 ongoing pregnancies in the aspirin (23.6%) and 147 in the placebo group (26.7%) [OR 0.85, 95% CI (0.65–1.1)]. Whereas the conventional meta-analysis limited to studies that could provide IPD showed an OR of 0.89 (95% CI 0.69–1.2), the conventional meta-analysis limited to the eight studies of which method of randomization could be confirmed showed an OR of 0.94 (95% CI 0.76–1.17) and the conventional meta-analysis including all 10 eligible RCTs identified with our search changed the OR to 1.07 (95% CI 0.81–1.41). This difference in direction of effect, derived from the studies not able to share IPD of which quality of randomization could not be confirmed.

CONCLUSIONS

Aspirin does not improve pregnancy rates after IVF.

BACKGROUND

Patients with polycystic ovary syndrome (PCOS) are at risk of arterial disease. We examined the risk of (non)fatal coronary heart disease (CHD) or stroke in patients with PCOS and ovulatory women without PCOS, and assessed whether obesity might explain a higher risk of CHD or stroke.

METHODS

We performed a systematic review and meta-analysis of controlled observational studies. Four definitions of PCOS were considered: World Health Organization type II anovulation, National Institutes of Health criteria, Rotterdam consensus and Androgen-excess criteria. Obesity was defined as BMI > 30 kg/m² and/or waist circumference >88 cm. Study quality was assessed using the Newcastle–Ottawa Scale. Primary outcome was fatal/non-fatal CHD or stroke. Definitions of CHD and stroke were based on criteria used by the various authors. The effect measure was the pooled relative risk in a random effects model. Risk ratios and rate ratios were combined here.

RESULTS

After identifying 1340 articles, 5 follow-up studies published between 2000 and 2008 were included. The studies showed heterogeneity in design, definitions and quality. In a random effects model the relative risk for CHD or stroke were 2.02 comparing women with PCOS to women without PCOS (95% confidence interval 1.47, 2.76). Pooling the two studies with risk estimates adjusted for BMI showed a relative risk of 1.55 (1.27, 1.89).

CONCLUSIONS

This meta-analysis showed a 2-fold risk of arterial disease for patients with PCOS relative to women without PCOS. BMI adjustment did not affect this finding, suggesting the increased risk for cardiovascular events in PCOS is not completely related to a higher BMI in patients with PCOS.

BACKGROUND

Complex chromosomal rearrangements (CCRs) describe structural rearrangements, essentially translocations, involving at least three breakpoints on two or more chromosomes. Although they are rare in humans, their clinical identification is important since CCR carriers can display various phenotypes which include phenotypically normal subjects, infertile males and patients with mental retardation and/or congenital abnormalities. The rearrangement can be de novo or familial. The use of fluorescent in situ hybridization assays and molecular techniques for the characterization of CCRs have indicated that the rearrangements could be more complex than initially assumed. Accumulating data have revealed that the mechanisms underlying the genesis of CCRs remain elusive.

METHODS

We performed a large PubMed search in order to summarize the current knowledge in this field and address important aspects of CCR formation and meiotic behavior, highlighting the complexity of these rearrangements at the chromosomal and genomic level.

RESULTS

The review of published data indicates that the complexity of CCRs is becoming increasingly known, thanks to the application of more and more efficient molecular techniques. These approaches have allowed the precise sequence analysis of breakpoints and the identification of insertions, deletions, inversions and recombination events. New models have been proposed for the formation of CCRs, based on replication-based mechanisms and specific sequence elements. Their meiotic behavior has been discussed in the light of these new molecular data.

CONCLUSIONS

Despite the increasing understanding of the mechanisms involved in their genesis, CCRs arise as unique, complex events for which the genetic and reproductive counseling of carriers remains a challenge.

BACKGROUND

Preimplantation  genetic diagnosis (PGD) has been stated to improve live birth rates compared with natural conception in couples with recurrent miscarriage (RM) carrying a structural chromosome abnormality. It is unclear to what extent this claim can be substantiated by evidence. A systematic review of the literature was performed on the reproductive outcome of these couples after natural conception or after PGD.

METHODS

MEDLINE, EMBASE and the Cochrane database were searched until April 2009. Trials, patient series and case reports describing reproductive outcome in couples with RM carrying a structural chromosome abnormality after natural conception and/or after PGD were included. Since no randomized controlled trials or non-randomized comparative studies were found, separate searches for both groups were conducted. Primary outcome measure was live birth rate per couple. Secondary outcome measure was miscarriage rate per couple.

RESULTS

Four observational studies reporting on the reproductive outcome of 469 couples after natural conception and 21 studies reporting on the reproductive outcome of 126 couples after PGD were found. After natural conception, live birth rate per couple varied between 33 and 60% (median 55.5%) after parental chromosome analysis; miscarriage rate ranged from 21 to 40% (median 34%). After PGD, live birth rate per couple varied between 0 and 100% (median 31%) after parental chromosome analysis; miscarriage rate ranged from 0 to 50% (median 0%).

CONCLUSIONS

Currently, there are insufficient data indicating that PGD improves the live birth rate in couples with RM carrying a structural chromosome abnormality.