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Biomedical subjects

K Wick

Publications and source records attributed to K Wick.

5 recordsLinked to original sources
PubMed1994

Birth characteristics and perinatal outcome of babies conceived from cryopreserved embryos.

The objective of this retrospective study was to compare the birth characteristics and perinatal mortality of babies conceived from the use of cryopreserved embryos with those resulting from in-vitro fertilization (IVF) and fresh embryo transfer. A total of 232 consecutive births, one pregnancy termination and a total of 283 babies in the cryopreserved group were studied. The IVF data included 763 births, three terminations and 961 babies, based on a previous analysis. There was no difference in the incidence of twin (18 versus 19%) and triplet births (2 versus 3%) in the cryopreserved and IVF groups respectively. The mean gestational age and birthweight of singleton, twin and triplet births were not significantly different between the groups. No difference was found in the perinatal mortality rates. The incidence of major congenital malformations in the cryopreserved group (1%) was significantly lower than that in the IVF group (3%; P < 0.05). It is concluded that the birth characteristics of babies conceived from cryopreserved/thawed embryos are similar to those from fresh embryos. There are fewer congenital malformations in the cryopreserved group.

Birth Weight↗
PubMed1991

Replacement of frozen-thawed embryos in artificial and natural cycles: a prospective semi-randomized study.

This prospective partly-randomized study assessed the relative efficacy of two strategies of patient management for the replacement of frozen-thawed embryos. A luteinizing hormone-releasing hormone (LHRH) agonist was used to induce a temporary hypogonadism in a group of patients who were then prepared for implantation by endometrial priming with hormone replacement therapy (HRT): oral oestradiol valerate and then oestradiol valerate and injections of progesterone. A second group of patients had their frozen-thawed embryos replaced during their natural cycles. Of the 84 patients treated with the LHRH regimen, 80 had embryos replaced and 16 (20%) clinical pregnancies were established. Of the 78 patients treated with natural cycles, 70 had embryos replaced and 14 (20%) achieved clinical pregnancies. There were no statistical differences between the two groups in terms of age, obstetric history, duration of infertility, number of oocytes retrieved and fertilized or the number of embryos frozen following ovarian stimulation in the embryo 'generating' cycle. In terms of pregnancy rates, both protocols were equally effective. However, the LHRH-HRT protocol was of great value in the management of oligomenorrhoeic patients and in establishing standard conditions for implantation in cyclic patients.

Cryopreservation↗
PubMed1990

Effect of cell number at freezing upon survival and viability of cleaving embryos generated from stimulated IVF cycles.

The survival of cleaving embryos after freezing and thawing has been assessed. First, comparisons were made of the proportions of embryos in which all blastomeres were viable cells after thawing, following various forms of ovarian stimulation. A flare-up protocol using a GnRH-agonist (buserelin) produced significantly higher numbers of these embryos than a pituitary down-regulation protocol (P less than 0.05), though neither was significantly different from clomiphene citrate/HMG stimulation. Secondly, other parameters of embryo survival e.g. proportions with one or more surviving cells and pregnancy rates were assessed and were similar among stimulation protocols and treatments in the embryo replacement cycle. Survival of blastomeres in 2- to 8-cell embryos was inversely related to the theoretical total surface area of all blastomeres in the embryo. Thawed embryos with one or more blastomeres damaged during freezing had the same capacity to produce pregnancies as did those with all blastomeres intact. The survival of individual cells was clearly related to the stage at which the cleaving embryo is frozen, but moderate loss of cells does not significantly influence implantation.

Blastomeres↗