The relationship of initial embryo crown-rump length to pregnancy outcome and abortus karyotype based on new growth curves for the 2-31 mm embryo

The objective of this study was to determine if measurementof initial crown-rump length (CRL) is helpful in predictinglow birth weight, newborn length, spontaneous abortions, orabortus karyotype. We measured CRL prospectively in 837 consecutivesingleton pregnancies at the time a heart rate was first detectablewith transvaginal ultrasonography and compared these measurementsto normal values for the 10th through 90th centiles determinedfrom 227 transvaginal ultrasound measurements in in-vitro fertilizationand gamete intra-Fallopian transfer pregnancies with known ovulationdates. The relationship of initial CRL to birth weight and lengthand to abortion and abortus karyotype was analysed after allpregnancies had delivered. Initial CRL measured after the 28thpost-ovulation day was predictive of subsequent abortion, butnot of low birth weight or length. The abortion rate was 3.3%[95% confidence interval (CI) 1.5%, 5.1%] when initial CRL50thcentile, compared to 19.4% (95% CI 15.4%, 23.4%) when <50thcentile. Initial CRL was <50th centile in 13 out of 14 trisomicand in eight out of 10 other karyotypically abnormal aborti.These results indicate that initial CRL measured after the 28thpost-ovulation day may help to identify pregnancies at increasedrisk of abortion due to abnormal karyotypes.     

Morphological and molecular characteristics of living human fetuses between Carnegie stages 7 and 23: ultrasound scanning and direct measurements

The developmental age of an embryo in the first trimester ofpregnancy is generally determined by ultrasound scanning and/orby calculation from menstrual age. In the original studies,validation of the estimate of gestational age by ultrasoundwas not possible as the exact date of conception was unknown.Variation in growth rates of identically aged fetuses has previouslybeen reported after assisted conception and with the use ofultrasound scanning. As these pregnancies were ongoing the accuracyof the scanning results could not be determined. Comparisonof scanning and direct measurements after termination of pregnancyand menstrual age were carried out to determine the accuracyin fetal dating. The results suggest that the use of ultrasoundscanning to determine gestational age is of less use than previouslythought, and that the use of menstrual age is severely limited.     

The probability of multiple births when multiple gestational sacs or viable embryos are diagnosed at first trimester ultrasound

The live birth outcome when multiple gestational sacs were diagnosed at first trimester ultrasound was reviewed in 227 twin, 43 triplet and five quadruplet pregnancies. When two gestational sacs were present, the probability of delivering twins was 63% for maternal age less than 30 and 52% for maternal age greater than or equal to 30. With three gestational sacs, the probability of a triplet birth was 45% for maternal age less than 30 and 18% for maternal age greater than or equal to 30. When two viable embryos were present, the probability of a twin birth was 90% for maternal age less than 30 and 84% for maternal age greater than or equal to 30. With three viable embryos, the probability of a triplet birth was 90% for maternal age less than 30 and 44% for maternal age greater than or equal to 30. Two gestations resulting from ovulation induction with clomiphene citrate were more likely to result in twin delivery at term, compared to spontaneous twin gestations (P = 0.012). These findings may be useful in the treatment and management of patients when multiple gestations are diagnosed early in pregnancy.     

Relationship of uterine blood flow to chorionic sac and embryo growth rates

The embryonic period of development is characterized by markedvariability in the rate of embryonic growth and development.Differences in uterine blood flow may explain this variability.We investigated the relationship between uterine artery bloodflow volume (VOL), uterine artery pulsatility index (UA-PI),uterine artery resistance index (UA-RI), spiral artery pulsatilityindex (SA-PI), spiral artery resistance index (SA-RI), chorionicsac diameter (CSD), and crown—rump length (CRL) during321 first trimester vaginal colour Doppler ultrasound examinationsof 94 delivered or continuing pregnancies. After correctingfor the confounding effect of gestational age, subject, andserum hormone levels by Analysis of Covariance, CRL was relatedto UA-PI (P equals; 0.025) and UA-RI (P <0.001), but notto VOL, SA-PI, or SA-RI. No relationship was found between CSDand any uterine blood flow variables. Serum oestradiol levelswere related to CSD and CRL (P < 0.001). No relationshipwas found to progesterone, maternal age, parity, or previousabortion. We conclude that differences in uterine blood flowand serum oestradiol explain some of the variability in therate of embryo growth during the first 12 gestational weeks.     

Prevention of twin pregnancy after in-vitro fertilization or intracytoplasmic sperm injection based on strict embryo criteria: a prospective randomized clinical trial.

A prospective randomized study comparing single embryo transfer with double embryo transfer after in-vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI) was carried out. First, top quality embryo characteristics were delineated by retrospectively analysing embryos resulting in ongoing twins after double embryo transfer. A top quality embryo was characterized by the presence of 4 or 5 blastomeres at day 2 and at least 7 blastomeres on day 3 after insemination, the absence of multinucleated blastomeres and <20% cellular fragments on day 2 and day 3 after fertilization. Using these criteria, a prospective study was conducted in women <34 years of age, who started their first IVF/ICSI cycle. Of 194 eligible patients, 110 agreed to participate of whom 53 produced at least two top quality embryos and were prospectively randomized. In all, 26 single embryo transfers resulted in 17 conceptions, 14 clinical and 10 ongoing pregnancies [implantation rate (IR) = 42.3%; ongoing pregnancy rate (OPR) = 38.5%] with one monozygotic twin; 27 double embryo transfers resulted in 20 ongoing conceptions with six (30%) twins (IR = 48.1%; OPR = 74%). We conclude that by using single embryo transfer and strict embryo criteria, an OPR similar to that in normal fertile couples can be achieved after IVF/ICSI, while limiting the dizygotic twin pregnancy rate to its natural incidence of <1% of all ongoing pregnancies.     

Relationship of initial chorionic sac diameter to abortion and abortus karyotype based on new growth curves for the 16th to 49th post-ovulation day

In order to determine whether initial chorionic sac diameteris related to subsequent abortion, abortus karyotype, or birthweight and length, chorionic sac diameter was prospectivelymeasured by transvaginal ultrasound in 700 singleton pregnanciesbefore post-ovulation day 31, the latest day cardiac activitybecomes detectable in normal pregnancy. Results were comparedto values for the 10th to the 90th centiles, determined from227 measurements of in-vitro fertilization and gamete intra-Fallopiantransfer pregnancies. The abortion rate was 23.9% [95% confidenceinterval (CI) 19.2%, 28.6%] when initial chorionic sac diameterwas below the 50th centile, compared to 6.9% (95% CI 4.9%, 9.4%)when equal to or above the 50th centile. Chorionic sac diameterwas below the 50th centile in all anembryonic abortions andin 62% of embryonic abortions. Triploidy, trisomy 47 + 16, ortrisomy 16 and the presence of satellite bodies on chromosome22 were the only abortus karyotypes significantly associatedwith small chorionic sac diameter. Initial chorionic sac diameterwas not associated with birth weight or length. We concludethat chorionic sac diameter is decreased in anembryonic andembryonic abortion and that normal pregnancy outcome may beexpected in 90–95% of pregnancies in which initial chorionicsac diameter is equal to or above average     

Factors determining early pregnancy loss in singleton and multiple implantations

BACKGROUND: The incidence of first trimester pregnancy loss is much lower in IVF twin pregnancies than in IVF singleton pregnancies. The objective of this study was to determine which embryonic and maternal factors contribute to this finding. METHODS: Retrospective data analysis of the outcome of 1593 pregnancies after day 3 double-embryo transfer (DET) after IVF or ICSI treatment. RESULTS: Of 1148 single implantations at 6 weeks, 936 (81.5%) were ongoing pregnancies. Of 445 multiple implantations at 6 weeks, 354 (79.6%) were ongoing multiple pregnancies, 80 (17.9%) were ongoing singleton pregnancies and 11 (2.5%) ended in a spontaneous abortion. Total pregnancy loss was 18.5 and 2.5% (P < 0.001) in singleton and twin gestations, respectively. Loss per gestational sac was 18.5 and 11.46% (P < 0.001), respectively. Determinants contributing to the continuation of gestation beyond 6 weeks were young maternal age, possibility to cryopreserve embryos and short GnRH agonist flare-up stimulation protocol. Whereas factors promoting multiple implantation at 6 weeks of gestation were young maternal age, high cumulative embryo score (CES), male infertility, long stimulation protocol and thick endometrium. CONCLUSIONS: Although multiple implantation at 6 weeks is predominantly determined by (morphological) embryo quality, the continuation of pregnancy beyond 6 weeks becomes more dependent on the combination of genetic and developmental potential of the embryo(s) and an optimal uterine milieu.     

Prevention of twin pregnancies after IVF/ICSI by single embryo transfer. ESHRE Campus Course Report

Twin pregnancies constitute the most serious complication for both mother and children after IVF/ICSI treatment, but transfer of at least two 'best looking' embryos remains the standard policy. This is due to our inability and reluctance to identify both the 'twin prone' patient and the top quality embryo. Some centres now electively transfer a single embryo (eSET) when particular embryo quality and patient criteria are met. Results from several centres were presented during an ESHRE Campus Course, held on May 6(th) 2000. Sound clinical trials are needed to clarify several points of discussion. What is the clinical profile of patients in whom eSET should be considered? Will the overall (ongoing) pregnancy rate of the IVF/ICSI programme decrease if eSET is performed in these patients? What is the twinning rate when eSET is a routine policy? Will the financial gain by avoiding perinatal hospitalization costs of prevented twins be balanced by the likely need to perform a number of extra IVF/ICSI cycles? What will be gained by freezing the extra number of high quality embryos? Should eSET be performed at the 2 pronuclear stage, the early cleaving embryo or the blastocyst stage? Common sense dictates that eSET as a concept should be applied from now onwards.     

Transvaginal ultrasound-guided embryo transfer improves pregnancy and implantation rates after IVF.

BACKGROUND: Attempts are constantly being made to improve clinical pregnancy rates after IVF and embryo transfer. Since November 1998, we have gradually been adopting transvaginal ultrasound guidance during embryo transfer. We retrospectively examined the efficacy of this method on pregnancy and implantation rates. METHODS: The results of 846 cycles from our IVF-embryo transfer programme were analysed and comparisons were made between those carried out using ultrasound guidance and those by the clinical touch method. RESULTS: Higher pregnancy and implantation rates (28.9 and 15.2% respectively) were found in the group using the transvaginal ultrasound guidance during embryo transfer compared with those in the group using the clinical touch method (13.1 and 7.0% respectively). The differences were statistically significant (P < 0.01). There was no significant difference in ectopic pregnancy rates between the two groups. CONCLUSION: The use of transvaginal ultrasound-guided embryo transfer significantly improved both pregnancy and implantation rates. Although technically difficult, we suggest its use may maximize the chances of achieving a successful pregnancy outcome.     

Ultrasound-guided embryo transfer improves pregnancy rates and increases the frequency of easy transfers

BACKGROUND: Recent reports have suggested that ultrasound (US) guidance during embryo transfer might improve pregnancy rates. METHODS: A prospective randomized (computer-generated random table) trial was performed to compare embryo transfer under abdominal US guidance (n = 255 women) with clinical touch embryo transfer (n = 260). RESULTS: The clinical pregnancy rate was 26.3% (67/255) in the US-guided transfer group compared with 18.1% (47/260) in the clinical touch transfer group (P < 0.05). The implantation rate was 11.1% (100/903) in the US group compared with 7.5% (66/884) in the clinical touch group (P < 0.05). US-guided transfer was associated with a decrease in the difficulty of the transfers: 97% of transfers were easy in the US-guided group compared with 81% in the clinical touch group (P < 0.05). CONCLUSIONS: US-guided embryo transfer increased pregnancy and implantation rates in IVF cycles, as well as the frequency of easy transfers. It is suggested that the decrease in cervical and uterine trauma can play a role in the increase in pregnancy rates associated with US-guided transfer. It is recommended that embryo transfer should be performed under US guidance.     

Development of the secondary human yolk sac: correlation of sonographic and anatomical features.

Transvaginal ultrasound examination of the secondary yolk sac was performed in 145 first trimester pregnancies with a normal outcome (Group A), in 10 normal pregnancies undergoing artificial termination (Group B) and in 25 pregnancies that subsequently failed (Group C) due to embryonic death (n = 17) or to spontaneous abortion of a live embryo (n = 8). The yolk sac structure of all cases from Group B and from 12 cases of Group C were examined morphologically, in order to investigate the changes secondary to normal yolk sac senescence or to pregnancy complication and to evaluate the relationship existing between these changes and ultrasound features. The yolk sac diameter measured in vivo increased significantly between 6 and 10 weeks of gestation and then decreased significantly. Morphologically, the yolk sac showed degenerative changes after 9 weeks of gestation suggesting that the disappearance of the yolk sac in normal pregnancies was a spontaneous event of embryonic development rather than the result of mechanical compression by the expanding amniotic cavity. Yolk sac measurements in complicated pregnancies were not predictive of pregnancy outcome. Irrespective of gestational age, important degenerative changes were found in pregnancies complicated by embryonic death or disappearance, suggesting that variation of yolk sac size and appearance in these cases is the consequence of abnormal embryonic development of death rather than being the primary cause of early pregnancy failure.     

Transfusion-dependent homozygous {beta}-thalassaemia major: successful twin pregnancy following in-vitro fertilization and tubal embryo transfer

Homozygous -thalassaemia (thalassaemia major) is a severe, transfusion-dependentanaemia that also causes infertility due to endocrine impairment.Very few pregnancies are reported among such patients and thereis only one report in the literature referring to a pregnancyachieved with ovulation induction and intra-uterine insemination.We report here the first successful twin pregnancy followingin-vitro fertilization and tubal embryo transfer in a transfusion-dependenthomozygous -thalassaemic woman with an oligoastheno-zoospermicpartner. Prior to ovarian stimulation, desferrioxamine was discontinueddue to potential fetotoxicity. Pre-gestational transfusionaland chelating therapies were resumed after delivery. In suchpatients, ovulation induction and assisted reproductive techniquesappear crucial in achieving pregnancy with concurrent haematologicalbalance without desferrioxamine administration.     

Fetal loss in the first trimester after demonstration of cardiac activity: relation of cytogenetic and ultrasound findings

A retrospective comparison of cytogenetic and ultrasound findingsin first trimester spontaneous fetal loss after demonstrationof cardiac activity was made. The crownrump length (CRL) wasmeasured twice for each fetus resulting in spontaneous abortion:(i) CRL was measured in the viable state while demonstratingcardiac activity, and the growth deviation was expressed asthe measured/ expected CRL ratio (M/E CRL ratio); (ii) in thesame fetus, CRL was measured after confirmation of fetal death,and designated as the post-mortem CRL. The chorionic tissuesof these abortuses were karyotyped. The CRL of fetuses whichresulted in normal deliveries were also measured as controls.As a result, 16 of 24 abortuses displayed an abnormal chromosomalanalysis (67%). Themean M/E CRL ratio of still-viable fetuseswas smaller than that of control fetuses (0.74 ± 0.20versus 0.98 ± 0.13 respectively, P < 0.01). The differencesin ratio between karyotypically normal and abnormal abortuseswere not statistically significant. The post-mortem CRL of deadfetuses was >20 mm in four of five monosomy X, two of three21-trisomy, one of three triploidy and none of eight embryoswith normal karyotype and five other trisomies. In conclusion,our study demonstrated that the M/E CRL ratio could be usedas a predictor of spontaneous abortions, although it does notdiscriminate abnormal karyotypes from normal ones. The embryoswith a post-mortem CRL more than 20 mm have a higher likelihoodof suffering monosomy X or 21-trisomy. The ultrasonographicfindings might offer a cytogenetic clue as to a possible causeto the developmental arrest.     

Elective single day 3 embryo transfer halves the twinning rate without decrease in the ongoing pregnancy rate of an IVF/ICSI programme

BACKGROUND: Data on the effect of elective single embryo transfer (eSET) on the total and multiple pregnancy rates of an IVF/ICSI programme are reported. METHODS AND RESULTS: A retrospective cohort analysis of eSET was carried out over a 4 year period. A total of 1559 cycles resulted in 1464 transfers; 299 transfers of one top quality embryo (20.4%) and 86 of one non-top quality embryo (5.9%) yielded 149 conceptions (49.8%) with 105 ongoing pregnancies (35.1%) and 26 conceptions (30.2%) with 19 ongoing implantations (22.1%) respectively; 1079 transfers of two (n = 853; 58.3%) or more than two (n = 226; 15.4%) embryos yielded 366 ongoing pregnancies (33.9%). The ongoing pregnancy rates for the years between 1998 and 2001 were 35.9, 27.9, 31.9 and 31.0% per oocyte retrieval and 38.5, 29.4, 34.1 and 33.2% per transfer. There were no differences in pregnancy rates between any of the years. The average ongoing pregnancy rate (>12 weeks) over the 4 years was 31.5% per started cycle and 33.5% per transfer; the average number of embryos transferred decreased from 2.26 (1998) to 1.79 (2001); the multiple pregnancy and twinning rates dropped from 33.6 and 29.5% (1998) to 18.6 and 16.3% (2001) respectively. CONCLUSIONS: Judicious application of eSET can halve the twinning rate while maintaining the overall pregnancy rate.     

Influence of position and length of uterus on implantation and clinical pregnancy rates in IVF and embryo transfer treatment cycles

In a prospective study of 807 consecutive women shown to have an apparently normal uterus after hysterosalpingography, hysteroscopy or pelvic ultrasonography prior to IVF or intracytoplasmic sperm injection (ICSI) and embryo transfer, the position and length of the uterine cavity was measured routinely at a pre-treatment mock transfer procedure. The apparent length of the uterine cavity was <7 cm in 128 women (group 1), 7-9 cm in 594 women (group 2) and >9 cm in 85 women (group 3). The uterus was noted to be retroverted in 38. 2% (308) women. The embryo transfer catheter was advanced to 5 mm from the uterine fundus based on the previously determined cavity length in all the embryo transfer procedures at 48 h after oocyte collection. Implantation and clinical pregnancy rates were not significantly different with respect to position of the uterus, difficulties encountered in passage of the catheter, mean age of the women, aetiology or duration of infertility or embryology events. An apparently greater cavity length was seen in older and/or parous women, but the difference was not statistically significant. Although the highest implantation and clinical pregnancy rates were seen in women with a cavity length of 7-9 cm (group 2) the differences were not statistically significant: group 1, 18.9 and 36. 7%; group 2, 21.0 and 46.5%; and group 3, 17.3 and 32.9% respectively. The incidence of ectopic pregnancy per reported clinical pregnancy was highest in group 1 women, being 14.9% (7/47) in comparison with group 2 (1.8%, 5/276) and group 3 (0%, 0/27) (P: < 0.0005), suggesting that the size of the uterus is a critical factor in the aetiology of ectopic pregnancy in IVF/ICSI-embryo transfer.     

Fertilization and early embryology: Incidence of microbial growth from the tip of the embryo transfer catheter after embryo transfer in relation to clinical pregnancy rate following in-vitro fertilization and embryo transfer

A total of 110 consecutive women was studied prospectively atthe time of transcervical embryo transfer followmg conventionalin-vitro fertilization and intracytoplasmic sperm injectionprocedures. Microbiological cultures were performed on endocervicalswabs and embryo transfer catheter tips. Positive microbialgrowths were observed from endocervical swabs in 78 (70.9%)women and from catheter tips in 54 (49.1%) women. The clinicalpregnancy rates were 57.1% in the group of patients withoutgrowth and 29.6% in the group with positive microbial growthfrom catheter tips. As microbial contamination at embryo transfermay influence implantation rates, prospective studies are justifiedto determine whether eradication of endocervical micro-organismsis possible and whether their eradication will improve implantationrates.     

Elective transfer of one embryo results in an acceptable pregnancy rate and eliminates the risk of multiple birth.

To avoid multiple pregnancies without compromising pregnancy rates (PR) is a challenge in assisted reproduction. We have compared pregnancy results among 74 elective one-embryo transfers (group 2) and 94 transfers where only one embryo was available (group 1). All the fresh embryo cycles during 1997 in two clinics in Helsinki were analysed, and cumulative PR among these couples after frozen-thawed embryo transfers up to June 1998 were counted. In group 2, where at least two embryos were available for transfer, and only one was transferred on day 2 or 3, the PR per embryo transfer was 29.7%. In group 1, the PR per embryo transfer was 20.2%. In group 2, the cumulative PR after frozen-thawed embryo transfers was 47.3% per oocyte retrieval. Over the same time, 742 two-embryo transfers were carried out. The PR per embryo transfer was 29.4% in these subjects, but 23.9% of these pregnancies were twins. The implantation rates, as well as the PR, were highest when the embryos were at the four- to five-cell stage on day 2 (35.8 versus 9.7% compared with the two- to three-cell stage, P < 0.001) or at the six- to eight-cell stage on day 3 (45.5%). The PR per embryo transfer was higher when a grade 1 or 2 embryo was transferred compared with a grade three embryo (34. 0 and 26.7% versus 8.8% respectively, P < 0.05). In women 35 years or younger, the PR per elective one-embryo transfer was 32.8%. The corresponding figure in women older than 35 years was 18.8%. On the basis of these results, elective one-embryo transfer can be highly recommended, at least in subjects who are younger than 35 years of age, and who have grade one or grade two embryos available for transfer.     

Ultrasound evidence for variability in the size and development of normal human embryos before the tenth post-insemination week after assisted reproductive technologies

Differences in human chorionic gonadotrophin (HCG), averagechorionic sac diameter, embryo/fetus crown —rump lengthand biparietal diameter were determined in 107 singleton pregnanciesdelivered after 34 weeks, whose post-insemination age was preciselyknown as a result of in-vitro fertilization (n = 28) or gameteintra-Fallopian transfer (n = 79). Crown — rump lengthswere interpreted in relation to the developmental stage of theembryo. A 7-fold to 10-fold difference in HCG levels was observedon post-insemination days 13–16. A 2-fold to 3-fold differenceoccurred in average chorionic sac diameter on days 25–36.A 2-fold difference occurred in crown — rump length onseven of 10 days prior to day 44. Biparietal diameter differedby no more than 42% from day 57–68 and 20% after day 68.Chorionic sac diameter, crown -rump length, and biparietal diameterwere also related to newborn weight. The results suggest firstlythat marked differences occur in the rate of early human development,secondly, that the differences occur prior to day 27 when observablecardiac activity begins, and thirdly, that the differences areminimized after day 68 when the embryonic period of developmentis completed.     

Computer analysis of the human embryo growth curve: Differences between published ultrasound findings on living embryos in utero and data on fixed specimens

Accurate information on the normal growth rate of the human embryo is fundamental to a better understanding of the embryonic period of pregnancy. Crown-rump length measured previously in utero (N = 227) with vaginal ultrasound in 107 in vitro fertilization (IVF) or gamete intrafallopian transfer (GIFT) singleton pregnancies was compared to the greatest length of fixed human embryos from the Carnegie collection, of known developmental stage whose postovulatory ages were estimated from menstrual histories. Average crown-rump length in utero was 60% of the greatest length of the fixed specimens prior to postovulation day 33, but were equal after postovulation day 40. The growth rate of in utero embryos and fixed specimens, analyzed by computer using exponential equations, was compared to linear and polynomial equations used in previously published embryo growth tables. The exponential equation, length = exp(a + b/age), fit in utero measurements best, while the equation length = exp[a + b/exp(age)] fit the fixed specimens best. Differences between length in utero and in fixed specimens may be related to distortion of the fixed embryos resulting from the formalin fixation, to ultrasound distortion, to curling of the embryo, or to incorrectly estimated ages of the fixed specimens. Study of human embryos in utero is now practical with vaginal ultrasound. © 1993 Wiley-Liss, Inc.