Comparison of FACSCount AF system, Improved Neubauer hemocytometer, Corning 254 photometer, SpermVision, UltiMate and NucleoCounter SP-100 for determination of sperm concentration of boar semen.

Current research aims at reducing the number of sperm per insemination dose thereby making measurement of sperm concentration in raw semen and the production of uniform insemination doses much more crucial. The present study evaluated the determination of sperm concentration using FACSCount AF System (FACS), Improved Neubauer hemocytometer (HEMO), Corning 254 photometer (Photo C254), SpermVision CASA System (SpermVision), UltiMate CASA System (UltiMate) and NucleoCounter SP-100 (SP-100). The instruments were evaluated with respect to repeatability and to establishing the regression curve towards both HEMO and FACS. Repeatability for the instruments was 2.7, 7.1, 10.4, 8.1, 5.4 and 3.1% for FACS, HEMO, Photo C254, SpermVision, UltiMate and SP-100, respectively. Correlation between instruments was highest between FACS and SP-100. This was made possible due to the high repeatability for both instruments. The agreement between the instruments and HEMO as the gold standard was lower than expected as the largest difference in estimation of concentration was -25 to +50%. The largest percentage difference was observed for measurements of dilute semen. It was clear that percentage difference between instruments depended on sperm concentration. In comparison to the gold standard, agreement was highest between SpermVision and HEMO for dilute semen, but for concentrated semen, agreement was highest between SP-100 and HEMO. However, the agreement between HEMO and all other instruments was not as good as expected. The reason may lie within the presence of agglutinated sperm, preventing proper HEMO counts.

Further considerations on natural or mild hyperstimulation cycles for intrauterine insemination treatment: effects on pregnancy and multiple pregnancy rates.

BACKGROUND: The high iatrogenic multiple pregnancy rate associated with intrauterine insemination (IUI) in hyperstimulated cycles is becoming less acceptable. Therefore we investigated data from an earlier prospective trial with regard to the specific question of whether the application of mild hyperstimulation in IUI cycles could be an alternative strategy for obtaining acceptable pregnancy rates while preventing a high multiple pregnancy rate, compared with natural cycles for IUI. METHODS: Pregnancy outcome of 310 natural and 334 mildly hyperstimulated cycles for IUI in 171 couples with unexplained or mild male factor subfertility was analysed on a patient level with random coefficient models. RESULTS: Pregnancy rates were similar: 35 and 39.8% per couple in the natural and mildly hyperstimulated cycles respectively (P = 0.60). Multiple pregnancies, all twin pregnancies, were conceived significantly more frequently in the mild hyperstimulation group (27% of the pregnancies) than in the natural cycle group (4% of the pregnancies) (P = 0.01). All multiple pregnancies in the hyperstimulation group were conceived in multifollicular cycles. Multifollicular development was strongly associated with the application of mild hyperstimulation only (odds ratio 21.14, 95% confidence interval 8.15-54.79). CONCLUSION: The application of a mild hyperstimulation protocol as an alternative to a standard hyperstimulation protocol for IUI does not result in higher pregnancy rates than IUI in the natural cycle, while at the same time multiple pregnancies cannot be avoided. Therefore, there is no place for the use of gonadotrophins in IUI treatment.

Ovarian response to standard gonadotrophin stimulation for IVF is decreased not only in older but also in younger women in couples with idiopathic and male subfertility.

BACKGROUND: With the occasional reports of unexpectedly poor ovarian response to controlled ovarian hyperstimulation (COH) for IVF in young normally cyclic women in mind, we studied age-related ovarian response to COH in a group of women who underwent standard IVF. METHODS: Ovarian response to COH was defined as the number of follicles > or = 14 mm on the day of hCG administration. Ovarian response to COH was analysed by multiple regression analysis with woman's age and basal FSH concentration as explanatory variables in a prospective cohort of patients with idiopathic and mild male factor subfertility (n = 85), and additionally in a large retrospective cohort of women with unexplained, mild male and tubal subfertility (n = 1155), with age as explanatory variable. RESULTS: Ovarian response to COH was associated significantly with age (P < 0.001) and basal FSH concentration (P = 0.002). However, in women with idiopathic or mild male subfertility, in both cohorts the relationship took the form of an inverted U-shape with both older and--surprisingly--young women having a reduced ovarian response (P < 0.001). Maximum ovarian response was around the age of 28 years. In women with tubal infertility, there was only a linear decline of ovarian response with age. CONCLUSION: It is hypothesized that diminished ovarian response to COH in IVF is the very first sign of ovarian ageing in young women diagnosed with idiopathic and mild male subfertility.

The postwash total progressively motile sperm cell count is a reliable predictor of total fertilization failure during in vitro fertilization treatment.

OBJECTIVE: To predict the chance of total fertilization failure (TFF) before the day of ovum pickup with known semen and female variables. DESIGN: A statistical model was constructed to predict TFF by retrospective analysis (2,366 couples) and subsequently tested on a new IVF population (917 couples). SETTING: Academic tertiary referral center. PATIENT(S): Three thousand three hundred eighty-three couples who underwent an IVF-ET treatment. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): The ability to predict the probability of TFF in IVF. RESULT(S): Two variables-postwash total progressively motile sperm cell count (postwash TPMC) and number of follicles-were found to be significant. Taking a probability of 25% as an acceptable risk of TFF, we calculated that a postwash TPMC of <1.1 x 10(6) cells results in a risk of TFF of >25%. Low responders (<4 follicles) needed a postwash TPMC of >2.2 x 10(6) cells to reduce the risk of TFF to <25%. High responders (>15 follicles) needed only 0.35 x 10(6) postwash progressively motile spermatozoa. CONCLUSION(S): When postwash TPMC and number of follicles are known and an unacceptable TFF outcome is expected, one can propose an ICSI procedure a few days before the day of ovum pickup.

The acrosome index, radical buffer capacity and number of isolated progressively motile spermatozoa predict IVF results.

BACKGROUND: The accuracy by which a number of newly described semen variables can predict either total fertilization failure (TFF) or pregnancy outcome in IVF, has not previously been investigated. The study aim was, therefore, to determine prospectively the predictive value of these variables. METHODS: The semen variables investigated were the post-wash total progressively motile sperm cell count (TPMC(post-wash)), the acrosome index (AI), 'cytoplasmic residues' and normal sperm morphology, evaluated according to the strict criteria ('strict criteria'), as well as the fast and slow total radical trapping antioxidant potential ('fast TRAP' and 'slow TRAP' respectively). RESULTS: The study group (n = 87) showed a mean (+/- SD) number of 10.2 +/- SD retrieved oocytes, 12.6% TFF, a mean fertilization rate of 59.7% and a pregnancy rate of 19.5% (17/87). TFF was significantly predicted by TPMC(post-wash), 'strict criteria', AI and 'cytoplasmic residues' (all P < 0.05). The outcome after embryo transfer was significantly predicted by AI and 'fast TRAP'. Semen samples with an AI <5% and a 'fast TRAP' <1.14 mmol/l in particular did not result in any pregnancies after IVF-embryo transfer. CONCLUSIONS: Of all the measured and calculated semen variables, TPMC(post-wash) was the best predictor of TFF, whilst AI and 'fast TRAP' were the best predictors of pregnancy after IVF.

Progressively motile human spermatozoa are well protected against in vitro lipid peroxidation imposed by induced oxidative stress.

Semen samples of 24 patients were analysed. Volumes were measured and the numbers of progressively motile (PMS), motile (MS) and nonmotile spermatozoa (NMS) were determined. These 24 samples appeared to show a large variation in motility percentages and numbers. Spermatozoa of these semen samples were isolated from the seminal plasma and exposed to induced radical oxygen stress imposed by iron/ascorbate. Lipid peroxidation (LPO) was quantified as thiobarbituric acid reactive material. The contributions of PMS, MS and NMS were also estimated. It was found that the PMS did not contribute to the formation of lipid peroxides. The cellular radical defence system of PMS may offer them adequate protection against the harsh conditions of radical oxygen stress. Stepwise regression analyses showed that only the population of NMS contributed significantly to the explanation of the variance in LPO production (R2 = 0.56, P < 0.001). Pre-existing membrane lipid peroxides were not detected in spermatozoa. It is therefore suggested that LPO takes place only after radical oxygen stress has exhausted the cellular defence system. LPO is not the initial, but one of the later, events leading to the death of spermatozoa. It is concluded that the population of progressively motile spermatozoa in semen samples does not contribute to the production of thiobarbituric acid reactive substances as induced by in vitro radical oxygen stress.

Health of human and livestock conceived by assisted reproduction.

Assisted reproduction is used to resolve infertility problems in human and in breeding programs to generate livestock. Except for gestation length and birth weight, perinatal outcome of children conceived by In Vitro Fertilization is similar to that of spontaneously conceived children. However, large offspring syndrome observed after In Vitro Production in livestock is quite alarming. The distinct parts of assisted reproduction (oocyte maturation, fertilization and culture) have been found to contribute to abnormal fetal growth and development. Genomic imprinting is suggested to be involved in the induction of the aberrant phenotypes observed after assisted reproduction. Furthermore, current knowledge on postnatal health of offspring conceived by assisted reproduction and speculations on potential longterm effects of In Vitro Fertilization will be described.

Quantification of the nonenzymatic fast and slow TRAP in a postaddition assay in human seminal plasma and the antioxidant contributions of various seminal compounds.

Total radical-trapping antioxidant potential (TRAP) measurements of human seminal plasma (N = 25) were performed by using a post-addition assay based on trapping 2,2' Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radicals. This method enables the antioxidant capacity of human seminal plasma and its constituents to be quantified. The standard procedure consisted of determination of the Trolox equivalent antioxidant capacity (TEAC) after incubating the test sample in the ABTS radical solution for 10 seconds (fast TRAP) and 300 s (total TRAP). Interestingly, seminal plasma showed a fast TRAP and a high slow TRAP (Total TRAP - Fast TRAP). The final total TRAP of seminal plasma is about 10 times higher than that of blood plasma. Various components of seminal plasma contribute to its fast TRAP; 37% can be attributed to vitamin C, uric acid, and tyrosine; proteins and polyphenolic compounds contribute a further 57%. In contrast, the slow TRAP was attributed to vitamin C (1%), uric acid (2%), and tyrosine (15%) and to proteins and polyphenolic compounds (33%). It was not possible to account for the remaining 49%. Neither known putative antioxidants, such as spermine, pyruvate, and taurine, nor other seminal compounds, such as carnitine, sialic acid, fructose, spermidine, glycerophosphorylcholine, and hyaluronic acid, contributed to any significant radical-trapping activity at a standard concentration of 1 mM. Of the amino acids, only tyrosine possessed a slow TRAP, and it is present at a high concentration in seminal plasma. Glutathione and hypotaurine show high fast and slow TRAPs, respectively. However, because of their low concentration in seminal plasma, their contribution to the TRAP is negligible. In conclusion, seminal plasma possesses a high antioxidant buffer capacity that protects spermatozoa from oxidative stress. Moreover, these findings suggest that the fast and slow TRAPs may have an important role as infertility markers and treatment targets in future antioxidant therapies.

Dose-finding study of triptorelin acetate for prevention of a premature LH surge in IVF: a prospective, randomized, double-blind, placebo-controlled study.

Gonadotrophin-releasing hormone agonists (GnRHa) are routinely used in IVF programmes to prevent an unwanted LH surge and consequent ovulation. Despite its widespread use in IVF, a convincing dose recommendation for GnRHa in IVF does not exist. In our opinion, the lowest possible dose of GnRHa should be used. Thus, we performed a prospective, randomized, double-blind, placebo-controlled study to determine the minimal daily dose of triptorelin acetate needed to suppress a premature LH surge during IVF treatment in a long protocol. A total of 240 women (60 in each group) was randomized to either placebo or to one of three doses of triptorelin, i.e. 15, 50 or 100 microg daily. Ovarian stimulation was performed with two or three ampoules of FSH daily. A premature LH surge occurred in 23% of placebo-treated patients, but in none of the triptorelin acetate-treated patients. There were significantly more oocytes and embryos in the 50 and 100 microg triptorelin groups. There was no dose relationship in rates of either implantation, pregnancy, ongoing pregnancy, live birth or baby take-home. In this study we showed that daily administration of 15 microg triptorelin is sufficient to prevent a premature LH surge, and that 50 microg is equivalent to 100 microg in terms of IVF results.

Obstetric outcome of singleton pregnancies after IVF: a matched control study in four Dutch university hospitals.

In singleton pregnancies after IVF a high rate of preterm deliveries and an increased rate of small-for-gestational age (SGA) children in comparison to the general parturient population have been reported. However, due to differences between IVF mothers and their peers who conceived naturally, careful selection of the control group is necessary to assess whether IVF pregnancies really carry increased risks of adverse outcome. In our study 307 IVF pregnancies were compared with 307 control pregnancies after elaborate matching for an extensive number of maternal characteristics, as well as for the hospital that provided the obstetric care. Four Dutch university hospitals contributed to the study. In cases with spontaneous onset of labour, gestational age at delivery was 3 days shorter in the IVF group (275 versus 278 days, P = 0.05). The proportion of SGA was higher in the IVF group (16.2 versus 7.9%, P < 0.001). The combination of these two results denotes a distinct difference between IVF and control pregnancies. Placental weight was comparable in both groups.

Tyrosine as important contributor to the antioxidant capacity of seminal plasma.

A novel post-addition method, based on the trapping of ABTS-radicals, is applied for studying the total antioxidant capacity of seminal plasma. A remarkable profile is observed, in which seminal plasma quenches radicals in a continuous, relatively slow fashion. Five putative antioxidants present in seminal plasma were studied using the same assay. Some of the compounds such as ascorbic acid, alpha-tocopherol and uric acid exert immediate, fast radical trapping, whereas hypotaurine and tyrosine give rise to the same slow radical trapping curve as seminal plasma. Due to this slow, continuous radical trapping, quantification of the total antioxidant capacity (expressed as trolox equivalent antioxidant capacity, TEAC) strongly depends on the chosen time point after onset of radical trapping. When determined during the slow antioxidant trapping phase, tyrosine has a powerful antioxidant capacity, which in combination with its relatively high plasma concentration makes it an important contributor to the total antioxidant capacity of seminal plasma.

Obstetric outcome of twin pregnancies after in-vitro fertilization: a matched control study in four Dutch university hospitals.

In singleton pregnancies after in-vitro fertilization (IVF), increased rates of obstetric and perinatal complications have been reported. Studies that compared IVF twin pregnancies with spontaneously conceived twins have yielded conflicting results. We compared 96 IVF twin pregnancies to 96 controls after elaborate matching. The design of our study precluded matching by zygosity. The monozygosity rate was higher in the control group and this implies that beforehand the risk for a less favourable outcome in the control group was higher than in the IVF group. However, the average birthweight of the IVF children was less than that of children in the control group (P = 0.04). This was not due to more intrauterine growth retardation in the IVF group. The mean gestational age at birth was 5 days shorter in IVF than control pregnancies, and although this difference was not significant it might explain the lower birthweight in the IVF group. The discordance rate in the IVF group was significantly increased. We found no difference in perinatal mortality and morbidity. We conclude that this study provides further evidence for a different outcome of IVF twin pregnancies in comparison with spontaneously conceived twin pregnancies.

In-vitro fertilization in a spontaneous cycle: easy, cheap and realistic.

The results of in-vitro fertilization in natural cycles (NIVF) in women with tubal infertility at our department are presented. The study had a prospective design. We needed 75 cycles in 50 patients to obtain one oocyte from each patient. Successful oocyte recovery rate was 67% per started cycle and 82% per oocyte retrieval. Thirty-five embryos were transferred and resulted in four ongoing pregnancies (5.3% per cycle, 6.5% per oocyte retrieval, 11.4% per embryo transfer and 11.4% per embryo). Six patients who participated in the study made a second attempt at NIVF. Five of them conceived of which four were ongoing. Cumulative ongoing pregnancy rates are 9. 8% per cycle, 11.9% per oocyte retrieval, 19.5% per embryo transfer and 19.5% per embryo. We conclude that NIVF is an easy, cheap and realistic method to obtain a pregnancy for patients with tubal infertility.

Intrauterine insemination or in-vitro fertilisation in idiopathic subfertility and male subfertility: a randomised trial and cost-effectiveness analysis.

BACKGROUND: Couples affected by idiopathic subfertility or male subfertility have an estimated spontaneous conception rate of about 2% per cycle. Although various infertility treatments are available, counselling of a couple in their choice of treatment is difficult because of the lack of consistent data from good-quality comparative studies. We compared the results of treatment with intrauterine insemination (IUI) with those of in-vitro fertilisation (IVF), and did a cost-effectiveness analysis. METHODS: In a prospective, randomised, parallel trial, 258 couples with idiopathic subfertility or male subfertility were treated for a maximum of six cycles of either IUI in the spontaneous cycle (IUI alone), IUI after mild ovarian hyperstimulation, or IVF. The primary endpoint was a pregnancy resulting in at least one livebirth after treatment. Cost-effectiveness based on real costs was studied by Markov chain analysis. FINDINGS: 86 couples were assigned IUI alone, 85 IUI plus ovarian hyperstimulation, and 87 IVF. Ten couples dropped out before treatment began. Although the pregnancy rate per cycle was higher in the IVF group than in the IUI groups (12.2% vs 7.4% and 8.7%, respectively; p=0.09), the cumulative pregnancy rate for IVF was not significantly better than that for IUI. Couples in the IVF group were more likely than those in the IUI groups to give up treatment before their maximum of six attempts (37 [42%] drop-outs vs 13 [15%] and 14 [16%], respectively; p<0.01). The woman's age was the only factor that influenced a couple's chance of success. IUI was a more cost-effective treatment than IVF (costs per pregnancy resulting in at least one livebirth 8423-10661 Dutch guilders [US$4511-5710] for IUI vs 27409 Dutch guilders [US$14679] for IVF). INTERPRETATION: Couples with idiopathic or male subfertility should be counselled that IUI offers the same likelihood of successful pregnancy as IVF, and is a more cost-effective approach. IUI in the spontaneous cycle carries fewer health risks than does IUI after mild hormonal stimulation and is therefore the first-choice treatment.

Gonadotrophin-releasing hormone agonist dose-dependency of pituitary desensitization during controlled ovarian hyperstimulation in IVF.

The aim of this study was to find the minimal effective daily s.c. dose of the gonadotrophin-releasing hormone (GnRH) agonist, triptorelin acetate, that suppresses the GnRH-induced release of luteinizing hormone (LH) at time of human chorionic gonadotrophin (HCG) injection and thereby prevents spontaneous LH surges during in-vitro fertilization (IVF) stimulation cycles. Therefore, a double-blind, prospective and randomized titration study was performed. A total of 48 IVF patients were divided into four groups of 12 patients. Each group received a different dose of triptorelin acetate, namely 5, 15, 50 or 100 microg s.c. daily. Standard ovarian stimulation was carried out using urinary follicle stimulating hormone (FSH) preparations. A 500 microg GnRH test was performed 90 min before the HCG injection in order to measure the degree of pituitary desensitization. Spontaneous LH surges were not detected in any of the groups, although three patients in the 5 microg group had ovulated at the time of ovum retrieval. The pituitary LH response to the GnRH test at time of HCG, expressed as area under the curve (AUC), appeared to be dose-dependent. Thus, a daily s.c. dose of 100 microg triptorelin acetate appears to be too high, since adequate desensitization of the pituitary (i.e. no spontaneous LH surge) can be achieved with doses as low as 15 and 50 microg.

An artificially induced follicle stimulating hormone surge at the time of human chorionic gonadotrophin administration in controlled ovarian stimulation cycles has no effect on cumulus expansion, fertilization rate, embryo quality and implantation rate.

In the spontaneous menstrual cycle, the mid-cycle gonadotrophin surge causes maturation of the cumulus-oocyte complex, mucification of cumulus cells and expansion of the cumulus oophorus, resumption of meiosis and maturation of the cytoplasm of the oocyte. Whether this is an effect purely of luteinizing hormone (LH) or whether follicle stimulating hormone (FSH) also plays a role is unknown. The effect of an artificially induced FSH surge at the time of human chorionic gonadotrophin (HCG) injection on maturation of the cumulus-oocyte complex was investigated in a prospective randomized double-blind trial. Twelve patients underwent controlled ovarian hyperstimulation [long gonadotrophin-releasing hormone agonist (GnRHa)/human menopausal gonadotrophin (HMG) protocol] for in-vitro fertilization (IVF) treatment. At the time of HCG administration, six patients received a bolus injection of FSH (450 IU i.m.); the other six patients received a placebo. The peak plasma concentrations of FSH of the experimental group were compared with the peak values of FSH obtained at the mid-cycle gonadotrophin surge of the natural cycle of a group of 12 volunteers to validate the bolus injection of FSH. Maturation of the cumulus-oocyte complex was quantified by measuring the expansion of the cumulus, by the fertilization rate and the implantation rate. The quality of the embryos was scored according the average morphology score. The bolus injection of FSH mimicked the mid-cycle gonadotrophin surge. The mean peak value of FSH (12.9 IU/l) in the experimental group was fully comparable with the mean peak value of FSH (10.0 IU/l) of the mid-cycle gonadotrophin surge in the natural cycle. No effect of a bolus injection of FSH on the maturation of the cumulus-oocyte complex or any other outcome variable was found. It is not advantageous to combine the final HCG injection with a bolus injection of FSH in GnRHa/HMG stimulated cycles.

Acrosomal morphology as a novel criterion for male fertility diagnosis: relation with acrosin activity, morphology (strict criteria), and fertilization in vitro.

OBJECTIVE: To determine the relationships between sperm acrosin activity, sperm morphology evaluated according to strict criteria, visually observed acrosomal morphology, and IVF rates. DESIGN: Prospective analytic study. Acrosin activity was determined on all semen samples together with a standard semen analysis. Emphasis was placed on sperm morphology and especially a novel criterion viz acrosome morphology (acrosome index) as recorded with bright field microscopy. SETTING: University-based tertiary care center. PATIENTS: Thirty-three couples undergoing IVF or GIFT with two or more metaphase II ova inseminated in vitro. MAIN OUTCOME MEASURE: In vitro fertilization rates of inseminated ova. RESULTS: Strong correlations were found between acrosome index, normal sperm morphology, and IVF rates. An acrosome index cutoff value could be established at > 10% normal acrosomes for IVF rates of > or = 50% (sensitivity and specificity = 100%) and an acrosin activity cutoff value at > 18 microIU/10(6) sperm. A multiple linear regression analysis showed that the acrosome index and acrosin activity added a significant contribution to the explanation of the variation in the fertilization rates. CONCLUSIONS: A strong positive correlation was found between acrosome index and IVF rates. Although the numbers of the study are small, the results indicate that the acrosome index possibly may be regarded as an additional tool in the prediction of IVF outcome and especially may be of value in the group of men with severe teratozoospermia, i.e., < or = 4% morphologically normal spermatozoa.

The probability of pregnancy after embryo transfer is affected by the age of the patient, cause of infertility, number of embryos transferred and the average morphology score, as revealed by multiple logistic regression analysis.

Because the process of conception is affected by many variables, a multiple logistic regression analysis was performed to assess (i) the impact and relative weight of both patient and embryo variables and (ii) their possible effects on the probability of a vital pregnancy after embryo transfer. A statistical model was constructed predicting the probability of pregnancy after embryo transfer. The variables that contributed significantly to the predictive value of the model were the age of the patient, the cause of infertility, the number of embryos transferred and the average morphology score of the transferred embryos. Embryo variables appeared to have a significant but modest value in predicting the probability of pregnancy after embryo transfer. Other variables, such as the thickness of the endometrium, were found to have no prognostic value. Moreover, we found that their effect could be explained by the variables already included in the model.

Time schedules of intrauterine insemination after urinary luteinizing hormone surge detection and pregnancy results.

A urinary luteinizing hormone (LH) test (LH Color, Organon, Oss, The Netherlands), was used to time intrauterine insemination in 177 cycles. Morning and evening urine samples were tested. In 58 women (33%) the test was positive in the morning urine sample. Fifteen of these patients were inseminated 8-10 h thereafter and one patient (6.7%) conceived. The remaining 43 women were inseminated the following day, 25-31 h after LH detection, and seven pregnancies (16.3%) ensued. In 119 cycles showing a positive urinary test in the evening sample, insemination was performed the next day, between 17 and 23 h after the LH surge, and 18 patients (15.1%) became pregnant. Statistical analysis showed no significant differences in pregnancy rates between the three different schedules, or in the time of insemination between conceptional and non-conceptional cycles within each group. Most ovulations occurred between 16 and 28 h after the positive test was observed. These findings suggest that while the lifespan of the gametes allows a relatively long period for fertilization, from 8 to 31 h after urinary LH surge detection, better results may be expected when inseminating about 24 (+/- 6) h after the positive test.