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S L Tan

Publications and source records attributed to S L Tan.

At least 145 records · Page 8Linked to original sources
PubMed1992

The routine use of gonadotropin-releasing hormone agonists for all patients undergoing in vitro fertilization. Is there any medical advantage? A prospective randomized study.

OBJECTIVE: To determine if the routine use of gonadotropin-releasing hormone agonists (GnRH-a) for all patients undergoing in vitro fertilization (IVF) produces any significant medical advantage. DESIGN: Prospective randomized study. PATIENTS: Three hundred eight patients having their first ever IVF attempt. INTERVENTIONS: Patients were randomly divided into four groups and received either human menopausal gonadotropin (hMG) alone for ovarian simulation (group A, n = 81); clomiphene citrate and hMG (group B, n = 77); a 3-day ultrashort course of GnRH-a and hMG (group C, n = 74); or pituitary desensitization with GnRH-a followed by hMG (group D, n = 76). RESULTS: The indications for IVF and mean age of all four groups of patients were comparable. There was a significant difference in the number of embryos cleaved and transferred among the groups, but there were no significant differences in the cancellation rate, mean number of oocytes collected or fertilized, and number of cases of failed fertilization. There were also no significant differences in the pregnancy and live birth rates per cycle commenced or per embryo transfer. CONCLUSION: The routine use of GnRH-a for all patients undergoing IVF has practical but no significant medical advantages.

Abortion, Spontaneous↗
PubMed1992

The long protocol of administration of gonadotropin-releasing hormone agonist is superior to the short protocol for ovarian stimulation for in vitro fertilization.

OBJECTIVE: To investigate whether pituitary desensitization with the gonadotropin-releasing hormone agonist (GnRH-a), buserelin acetate, before the administration of human menopausal gonadotropin (hMG) for ovarian stimulation in in vitro fertilization (IVF) is superior to the simultaneous administration of both hormones at the beginning of the treatment cycle. DESIGN: Prospective randomized study. PATIENTS: Ninety-one patients having their first attempt at IVF. INTERVENTIONS: Patients in group 1 (long protocol) were administered subcutaneous (SC) buserelin acetate 200 micrograms/d from day 1 of the menstrual cycle, and hMG was started only after pituitary desensitization had been achieved at least 14 days later. Patients in group 2 (short protocol) were administered SC buserelin acetate 200 micrograms/d from day 2 and the same dose of hMG used in the long protocol from day 3 of the menstrual cycle. RESULTS: The median total amount of hMG required in both groups was comparable. There were significantly more follicles (P = 0.0001), oocytes (P = 0.0008), fertilized oocytes (P = 0.0001), and cleaved embryos (P = 0.0001), and a higher fertilization rate (P = 0.0047) in patients in group 1. The pregnancy rates per initiated cycle and per embryo transfer were 19.57% and 25.71% in group 1 compared with 8.89% and 16.67% in group 2. CONCLUSIONS: The long protocol is superior in terms of significantly greater follicular recruitment, oocyte recovery and fertilization rates, and significantly greater number of embryos available for transfer. In general, it is the preferred method when GnRH-a are used for ovarian stimulation in IVF.

Adult↗
PubMed1992

Transvaginal peritoneal oocyte and sperm transfer for the treatment of nontubal infertility.

OBJECTIVE: To investigate if peritoneal oocyte and sperm transfer (POST) performed transvaginally is an effective treatment for nontubal infertility. DESIGN, SETTING, AND PATIENTS: Prospective study of 18 patients (4 with unexplained infertility, 13 with failed donor insemination, and 1 with male factor infertility) having 20 cycles of transvaginal POST in a specialist infertility unit. INTERVENTIONS: Ovarian stimulation was achieved with human menopausal gonadotropin (hMG) alone, hMG and clomiphene citrate, or gonadotropin-releasing hormone agonist with hMG. Oocyte recovery was performed transvaginally under ultrasound guidance, the pouch of Douglas rinsed repeatedly and an embryo transfer catheter used to transfer 4 x 10(6) progressively motile sperm in 1 mL and up to four oocytes into the pouch of Douglas. Luteal support was provided with human chorionic gonadotropin injections given 2 and 5 days later. RESULTS: The mean age of the patients was 32.65 +/- 5.0, and the mean length of infertility 5.07 +/- 2.32 years. The mean number of oocytes transferred was 3.53 +/- 0.87. Three pregnancies were achieved in the failed donor insemination group and 1 each in those with unexplained and male factor infertility, giving overall clinical pregnancy and live birth rates of 25% and 20% per initiated cycle. All pregnancies were achieved in those who had three or four oocytes transferred. CONCLUSION: Transvaginal POST is a useful assisted conception technique for the treatment of nontubal infertility.

Adult↗
PubMed1992

A prospective randomized study of the optimum timing of human chorionic gonadotropin administration after pituitary desensitization in in vitro fertilization.

OBJECTIVE: To determine if there is an optimum time for the administration of human chorionic gonadotropin (hCG) after pituitary desensitization with gonadotropin-releasing hormone agonists (GnRH-a) has been achieved before ovarian stimulation for in vitro fertilization (IVF). DESIGN: Prospective randomized study. PATIENTS: Two hundred forty-seven patients undergoing an IVF treatment cycle who were randomly divided into three groups. INTERVENTIONS: All patients were administered subcutaneously buserelin acetate 500 micrograms/d from day 1 of the menstrual cycle. After pituitary desensitization had been achieved at least 14 days later, ovarian stimulation with human menopausal gonadotropin was commenced. Ovarian stimulation, cycle monitoring, oocyte recovery, and IVF and embryo transfer (ET) techniques were identical in all three groups. Patients in group 1 (n = 79) had hCG administered when the mean diameter of the largest follicle had reached 18 mm, at least two other follicles were greater than 14 mm, and serum estradiol (E2) levels were consistent with the number of follicles observed on ultrasound. Patients in groups 2 (n = 84) and 3 (n = 84) had hCG administered 1 day and 2 days, respectively, after the above criteria had been reached. RESULTS: The mean day of hCG administration (P less than 0.01), maximum serum E2 concentration (P = 0.06), number of days of serum E2 rise (P = 0.03), and mean diameter of the largest follicle (P less than 0.0001) were significantly different. There were, however, no significant differences in the mean number of preovulatory and medium size follicles, number of oocytes recovered or embryos transferred. There were also no significant differences in the oocyte recovery, fertilization and cleavage rates, in the number of embryos frozen, or in the pregnancy rates per initiated cycle and per ET. CONCLUSIONS: There is no significant advantage in the precise timing of hCG administration after pituitary desensitization with GnRH-a.

Adult↗
PubMed1992

The administration of glucocorticoids for the prevention of ovarian hyperstimulation syndrome in in vitro fertilization: a prospective randomized study.

OBJECTIVE: To determine if the administration of glucocorticoids reduced the rate of ovarian hyperstimulation syndrome (OHSS) in high-risk patients after ovarian stimulation for in vitro fertilization (IVF). DESIGN: Prospective randomized study. PATIENTS: Thirty-one patients who were stimulated with human menopausal gonadotropin (hMG) after pituitary desensitization by gonadotropin-releasing hormone agonist and who developed greater than 20 follicles greater than 12 mm and/or had a serum estradiol (E2) level of greater than 10,000 pmol/L on the day of administration of human chorionic gonadotropin (hCG). INTERVENTIONS: Patients were randomly divided into two groups. Those who were randomized to receive glucocorticoids (group A) (n = 17) were administered intravenous hydrocortisone, 100 mg, immediately after ultrasound (US)-directed oocyte recovery. Prednisolone, 10 mg three times per day, was given for 5 days starting on the day of oocyte recovery followed by prednisolone 10 mg two times a day for 3 days and 10 mg/d for 2 days. Those in group B (n = 14) did not receive any glucocorticoid treatment. In both groups, luteal support was provided by intramuscular injections of gestone 100 mg/d. RESULTS: The two groups of patients were comparable in terms of age, duration of infertility, and total dose of hMG used. All had polycystic ovaries on US examination. On the day of hCG administration, the mean number of follicles in the two groups were 26.76 +/- 2.49 and 25.93 +/- 1.44 and the serum E2 concentration 13,404 +/- 710 and 13,915 +/- 901 pmol/L, respectively. There were no significant differences in the number of oocytes collected or in the fertilization, cleavage, and implantation rates in the two groups. The pregnancy rates per initiated cycle were 41.18% and 35.71%, respectively. Seven of the 17 patients (41.2%) who received glucocorticoids developed ovarian hyperstimulation syndrome compared with 6 of the 14 patients (42.9%) who did not receive glucocorticoids. CONCLUSIONS: Administrations of glucocorticoids to high risk patients did not reduce the rate of OHSS after ovarian stimulation for IVF.

Adult↗
PubMed1992

A prospective randomized study comparing aspiration only with aspiration and flushing for transvaginal ultrasound-directed oocyte recovery.

OBJECTIVE: To compare aspiration only with aspiration and flushing of ovarian follicles during transvaginal ultrasound (US)-directed oocyte recovery. DESIGN: Prospective randomized study. PATIENTS: One hundred patients who were undergoing an in vitro fertilization (IVF) treatment cycle. INTERVENTIONS: All patients underwent pituitary desensitization before the administration of gonadotropins. Monitoring of ovarian stimulation and the criteria for the administration of human chorionic gonadotropin were similar in both groups. In patients in whom aspiration alone was used, each follicle was aspirated until it was empty. The US probe was then rotated until every drop of follicular fluid had been aspirated before the next follicle was aspirated and the procedure repeated. For patients who had aspiration and flushing, each follicle was aspirated and then flushed up to a maximum of six times before moving to the next follicle. In both groups, all follicles greater than 10 mm were aspirated. RESULTS: The indication for IVF and mean age of the patients were comparable in the two groups. There were no significant differences between the aspiration and the aspiration and flushing groups in terms of the number of oocytes retrieved (11 versus 9), the oocyte recovery rates (77.5% versus 77.0%), the fertilization rates (55.6% versus 60.0%), the number of embryos transferred (2 versus 2), or the number of clinical pregnancies (12 versus 13). The time taken for oocyte recovery was significantly shorter (15 versus 30 minutes, P less than 0.00001), and the dose of pethidine required significantly less (50 mg versus 100 mg, P less than 0.00001) in the aspiration only group. CONCLUSIONS: Aspiration alone produces comparable oocyte recovery rates as aspiration and flushing while significantly reducing the length of the procedure and the dose of analgesia required. Aspiration alone suffices for virtually all cases during transvaginal US-directed oocyte recovery.

Adult↗
PubMed1992

The cumulative embryo score: a predictive embryo scoring technique to select the optimal number of embryos to transfer in an in-vitro fertilization and embryo transfer programme.

In order to achieve a clinical pregnancy rate higher than that achieved following initial adoption of in-vitro fertilization embryo transfers, more than one embryo is transferred. This has led to a substantial increase in unwanted multiple pregnancy rates with IVF as compared with natural conception. What is therefore required is a simple, clinically useful embryo scoring system, to reflect embryo developmental potential, which will enable the selection of the optimal number of embryos to transfer in order to achieve the maximum pregnancy rate with a low incidence of high order multiple pregnancies. We believe that the Cumulative Embryo Score (CES) achieves these aims. On the day of embryo transfer the grade of each embryo transferred was multiplied by the number of blastomeres to produce a score for each embryo, and summation of the scores obtained for all the embryos transferred gave the CES. The grouped pregnancy rates obtained rose as the CES increased to maximum of 42. A continued increase in the CES above 42 did not result in any further rise in the pregnancy rate. However, an analysis of all our IVF pregnancies showed that the multiple pregnancy rate continued to rise above a CES of 42. By restricting the CES per embryo transfer to 42, 78% of triplet pregnancies and 100% of the quadruplet IVF pregnancies could have been predicted and potentially avoided.

Adult↗
PubMed1992

In-vitro fertilization and the ovarian hyperstimulation syndrome.

Eight patients who developed severe ovarian hyperstimulation syndrome (OHSS) were identified among 1302 patients undergoing in-vitro fertilization (IVF) over a 1 year period (prevalence of 0.6%); 63% had ultrasonically diagnosed polycystic ovaries (PCO) and 75% were undergoing their first attempt at IVF. Pretreatment with a superactive luteinizing hormone-releasing hormone (LHRH) analogue significantly increased the prevalence of severe OHSS (1.1% versus 0.2%, P less than 0.05) compared with ovarian stimulation with clomiphene citrate and human menopausal gonadotrophin (HMG). The mean serum oestradiol concentration on the day of human chorionic gonadotrophin (HCG) administration was 8200 +/- 2300 pmol/l. A mean of 19.6 +/- 6.8 follicles had been aspirated and 13.1 +/- 7.7 oocytes recovered at transvaginal ultrasound-directed oocyte recovery. All patients had an embryo transfer and luteal support in the form of HCG. The clinical pregnancy rate was 88%, multiple pregnancy rate 71% and implantation rate 63.5 +/- 41.3%. In a group of seven patients who were hospitalized for moderate OHSS during the same period, peak oestradiol levels were significantly lower than in those with severe OHSS (P less than 0.05). Of the group with moderate OHSS, 57% had PCO, the clinical pregnancy rate was 100% and multiple pregnancy rate 43%. Patients with ultrasound-diagnosed PCO have an increased risk of developing OHSS and the dose of HMG administered to them should be minimized. In patients at risk of developing OHSS, progesterone instead of HCG should be used for luteal support. Transfer of a maximum of two embryos or freezing all embryos for transfer in a subsequent cycle may reduce the likelihood of multiple pregnancy.

Adult↗
PubMed1992

A prospective study comparing the outcome of oocytes retrieved in the aspirate with those retrieved in the flush during transvaginal ultrasound directed oocyte recovery for in-vitro fertilization.

OBJECTIVE: To study prospectively the fate of oocytes collected from the follicular aspirate and subsequent flushes during transvaginal ultrasound directed oocyte recovery for in-vitro fertilization (IVF). SETTING: A tertiary referral assisted conception centre. SUBJECTS: 100 consecutive patients undergoing 100 cycles of IVF. Four patients were withdrawn because their embryos were electively cryopreserved. Therefore 96 cycles were studied. MAIN OUTCOME MEASURES: The oocyte recovery rate, viability, fertilization and cleavage rates and outcome of embryos generated from oocytes that were obtained from either the initial aspirate (A1), dead space in the collecting system (A2) or the first two 2 ml flushes (F1 and F2) were compared. RESULTS: The overall oocyte recovery rate was 87.8%. Of the 1046 oocytes collected, 40.3% were from A1, 41.3% from A2, 13.7% from F1 and 4.7% from F2. There were comparable numbers of viable and fertilized oocytes and cleaved, transferred and frozen embryos in tubes A1 and A2 but all these parameters were significantly lower in tubes F1 and F2 (P < 0.0001). All these parameters were also significantly higher in F1 compared with F2 (P < 0.001), except for the number of embryos frozen, in which there was no difference. The overall pregnancy rate per cycle was 28.1% and the pregnancy rate per embryo transfer was 31.0%. There were no pregnancies in any of the cycles in which embryos originating from F2 were transferred, nor were there pregnancies in cycles in which only embryos from F1 were transferred. CONCLUSION: Follicular aspiration together with one 2 ml flush maximises the recovery of oocytes that will result in pregnancies.

Adult↗
PubMed1992

The use of luteinising hormone releasing hormone agonists for ovarian stimulation in assisted reproductive technology.

Although the use of luteinising hormone releasing hormone (LHRH) agonists and human menopausal gonadotrophin (hMG) for ovarian stimulation in assisted reproductive technology has gained wide-spread popularity, a number of major issues regarding their use remain unresolved. In this paper, we examine some of these issues in the light of the results of our own studies. We have found that although the use of LHRH agonists may be advantageous for some patients, its routine use for all patients produces no significant medical advantage compared with conventional stimulation regimens. In a number of prospective randomised studies, we have found that the long protocol of LHRH agonist administration is superior to the short and ultrashort protocols and the administration of glucocorticoids to patients at high risk of developing ovarian hyperstimulation syndrome does not reduce the incidence of this complication. Finally, we have found that when the long protocol of LHRH agonist administration is used, precise timing of human chorionic gonadotrophin administration (hCG) is not important. There are no significant differences in oocyte recovery, fertilisation and cleavage rates, or in pregnancy rates when the results of standard timing of hCG administration are compared with delayed administration. It would, therefore, appear that the major advantage of the routine use of LHRH agonists is for practical, rather than medical reasons.

Buserelin↗
PubMed1991

Heterotopic pregnancies after in vitro fertilization and embryo transfer.

Seventeen cases of heterotopic pregnancies are reported among 1648 clinical pregnancies after in vitro fertilization. The high prevalence of tubal damage among IVF patients and the use of superovulation and multiple embryo transfer might predispose patients to the condition. Nine patients reported abdominal pain and vaginal bleeding, five patients did not have symptoms, and three had acute abdominal emergencies. Transvaginal ultrasonography was superior to transabdominal ultrasonography in the diagnosis of extrauterine pregnancies. The presence of an intrauterine gestation sac in a patient without symptoms should not exclude the diagnosis of a concomitant extrauterine pregnancy until the pelvis is carefully visualized. Early diagnoses of viable ectopic pregnancies before rupture abolishes mortality and morbidity and offers the chance of patient selection for conservative treatment. In two patients the extrauterine gestation sac was treated by transvaginal aspiration and injection of potassium chloride under ultrasonographic guidance. The outcome of the intrauterine pregnancy was favorable regardless of the method of treatment of the ectopic pregnancy.

Abdomen↗
PubMed1991

The optimum dose and mode of administration of luteinizing hormone releasing hormone analogue in in-vitro fertilization: a comparison of three regimens.

Three regimens for administration of the luteinizing hormone releasing hormone analogue (LHRHa), buserelin, were compared in terms of pituitary down-regulation prior to ovarian stimulation for in-vitro fertilization (IVF). Thirty-three patients who had failed to conceive in previous IVF cycles were randomly divided into three groups. Patients in Group I (n = 11) received intranasal (i.n.) buserelin 200 micrograms four hourly for 21 days; patients in Group II (n = 11) received subcutaneous (s.c.) buserelin 500 micrograms twice a day for 7 days, followed by 500 micrograms daily for 14 days; patients in group III (n = 11) received (s.c.) buserelin 500 micrograms three times a day for 7 days. In all three groups administration of buserelin was continued until serum oestradiol levels were less than 100 pmol/l, at which time human menopausal gonadotrophin (HMG) was commenced. All the patients achieved pituitary down-regulation after seven days of treatment with buserelin, except for four patients who developed ovarian cysts and two with polycystic ovarian disease. The total dose of HMG used and the ongoing pregnancy rate were not significantly different between the three groups. A much higher proportion of patients in Group I developed side-effects and found their treatment disruptive to their life-style. Our results suggest that patient variables (e.g. polycystic ovaries, ovarian cysts) rather than the dose and mode of administration of buserelin, are the major determinant of the length of time needed for pituitary down-regulation. The s.c. route is preferable and the smallest dose of buserelin that will produce pituitary down-regulation should be used.

Adult↗
PubMed1991

Perinatal outcome and congenital malformations in in-vitro fertilization babies from the Bourn-Hallam group.

The perinatal outcome and congenital malformations in children born between 1978 and 1987 in Great Britain after in-vitro fertilization (IVF) at Bourn Hall Clinic and the Hallam Medical Centre are presented. The average maternal age was 34.2 years. Multiple births were frequent, constituting 23% of all deliveries; 19% were twins and 4% triplets. There were no quadruplet or higher order multiple births during that period. Twenty-five per cent of all deliveries were preterm. The mean birth weight was 2793 g and was strongly related to multiplicity of pregnancy and gestational age. Overall, 32% of babies had a low birthweight (less than 2500 g) with 6% having a very low birthweight (less than 1500 g). The overall stillbirth and infant mortality rates were two to three times higher than those of infants born after natural conception in England and Wales; this is attributed to the high incidence of multiple births. The stillbirth rates were 5.07, 20.8 and 24.7 per thousand total births in singletons, twins and triplets respectively. The corresponding figures for perinatal mortality were 13.5, 38.2 and 37 per thousand. Overall, 2.5% of the babies had one or more major congenital malformations diagnosed within one week of life. This was within the range of expected values in the United Kingdom and there was no significant increase in any specific malformation.

Adult↗
PubMed1990

Surgical techniques of oocyte collection and embryo transfer.

In the decade since the birth of the first child conceived as a result of in vitro fertilization and embryo transfer much has been achieved in the field of assisted conception. Although in vitro fertilization (IVF) was successful first for the treatment of tubal disease, the indications for its use have now widened to include unexplained infertility, oligozoospermia, endometriosis and infertility due to immunological disorders. Gamete intrafallopian transfer (GIFT) and zygote intrafallopian transfer (ZIFT) are now used commonly for the treatment of couples where the woman has patent fallopian tubes. The huge increase in the demand for therapy using these techniques of assisted conception places considerable strain on the finances available for health care, and has led some to question the wisdom of such use of limited resources. To reduce the cost of treatment, and because repeated IVF-ET attempts may be necessary before achieving pregnancy, the initial laparoscopic approach for oocyte recovery has been largely replaced by ultrasound-guided techniques. Non-surgical embryo transfer techniques have changed little since originally described. However, where the tubes are patent, one-cell zygotes or cleavage stage embryos may be transferred into the fallopian tube (ZIFT and tubal embryo stage transfer respectively). On the other hand if the tubes are blocked, surgical embryo transfer (SET) may be performed. Most recently, some success has been achieved following the transfer of embryos into the fallopian tube by the technique of retrograde fallopian tube catheterisation.

Biopsy, Needle↗
PubMed1990

Outcome of pregnancies resulting from assisted conception.

With the increasing practice of assisted conception, the health of the resulting children is becoming an increasingly important issue. Experience with four thousand children conceived by IVF or GIFT indicates that multiple pregnancy, which frequently results from assisted conception, is the main determinant of complications during pregnancy and of the health of the children at the time of birth. Overall malformation rates are similar to those in the country as a whole. There are, however, still insufficient numbers of children studied to draw firm conclusions about the risk of specific types of malformations. This will require the continued monitoring of children resulting from assisted conception, and the continued co-operation of many individuals and centres practising assisted conception.

Adult↗