The DOI matches its Crossref record; 33 of the 33 references it cites were found in a registry or an index; 2 of the 23 sources its claims cite were checked for support.
Time of Implantation of the Conceptus and Loss of Pregnancy
Open accessAbstract
BACKGROUND: Implantation of the conceptus is a key step in pregnancy, but little is known about the time of implantation or the relation between the time of implantation and the outcome of pregnancy. METHODS: We collected daily urine samples for up to six months from 221 women attempting to conceive after ceasing to use contraception. Ovulation was identified on the basis of the ratio of urinary estrogen metabolites to progesterone metabolites, which changes rapidly with luteinization of the ovarian follicle. The time of implantation was defined by the appearance of chorionic gonadotropin in maternal urine. RESULTS: There were 199 conceptions, for 95 percent of which (189) we had sufficient data for analysis. Of these 189 pregnancies, 141 (75 percent) lasted at least six weeks past the last menstrual period, and the remaining 48 pregnancies (25 percent) ended in early loss. Among the pregnancies that lasted six weeks or more, the first appearance of chorionic gonadotropin occurred 6 to 12 days after ovulation; 118 women (84 percent) had implantation on day 8, 9, or 10. The risk of early pregnancy loss increased with later implantation (P<0.001). Among the 102 conceptuses that implanted by the ninth day, 13 percent ended in early loss. This proportion rose to 26 percent with implantation on day 10, to 52 percent on day 11, and to 82 percent after day 11. CONCLUSIONS: In most successful human pregnancies, the conceptus implants 8 to 10 days after ovulation. The risk of early pregnancy loss increases with later implantation.
Overview
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Written from the paper’s full text.
TL;DR
In 189 naturally conceived pregnancies, implantation usually occurred 8 to 10 days after ovulation, and later implantation was strongly associated with higher risk of early pregnancy loss. The authors conclude that most successful human pregnancies implant 8 to 10 days after ovulation, while late implantation may reflect impaired embryo quality or reduced uterine receptivity.
Key findings
- Among 189 analyzed pregnancies, 141 (75 percent) lasted at least six weeks past the last menstrual period, and 48 (25 percent) ended in early loss.
- Among pregnancies lasting at least six weeks, first urinary chorionic gonadotropin appeared 6 to 12 days after ovulation; 118 women (84 percent) implanted on day 8, 9, or 10.
- Risk of early loss increased with later implantation (P<0.001): 13 percent among 102 conceptuses implanting by day 9, 26 percent on day 10, 52 percent on day 11, and 82 percent after day 11.
- Early losses had a later and broader implantation distribution (mean, 10.5 days; range, 6 to 18 days), whereas live births and clinical losses had mean implantation times of 9.1 and 9.2 days, respectively (P=0.59).
Methods
- Prospective study of 221 women with no history of fertility problems who were attempting to conceive after stopping contraception; they collected daily first-morning urine specimens through the eighth week of clinical pregnancy or for up to six months.
- Day of ovulation was estimated from the urinary ratio of estrone 3-glucuronide to pregnanediol 3-glucuronide, validated against the luteinizing hormone surge; implantation was defined as the first day urinary chorionic gonadotropin exceeded 0.015 ng per milliliter, with pregnancy defined as concentrations above 0.025 ng per milliliter for at least three consecutive days.
- Distributions of implantation times were compared with contingency-table chi-square statistics, and trend in early loss with later implantation was tested by logistic regression with two-sided P values.
Limitations
- Stated: implantation cannot be directly observed, and chorionic gonadotropin appearance may not mark the earliest implantation steps; random errors in ovulation and chorionic gonadotropin measures may spread the observed implantation distribution, so the true biologic window may be narrower.
- Stated: fertility treatment may distort reproductive function, so findings from these naturally conceiving women may not apply to treated infertility populations.
- Evident from the text: 10 pregnancies (5 percent) were excluded because ovulation or implantation day could not be determined due to missing data, and the sample comprised women without known fertility problems, limiting generalizability.
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Claims the paper makes
15 Own result · 11 Own interpretation · 9 No full text of the sources · 3 Not checked yet · 3 Own method · 1 Supported so far · 1 Couldn’t confirm · accuracy not yet measured
The sources with a verdict support this claim; the rest weren’t checked yet, have no full text we could read, or their verdicts aren’t rated yet.
In the paper
“There are no undisputed markers in humans of uterine receptivity to a fertilized ovum other than implantation itself.23,24”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
What the sources say
- Supportedcites [23] Younis JS, 1996, Fertil Steril source
The Conclusions (page unavailable) say that adequate endometrial morphology does not always imply normal receptivity and that more sensitive assessments are needed. They describe ultrasound, pinopodes, and integrins only as preliminary proposals, consistent with the claim that no marker other than implantation was undisputed. (LLM, conf=0.84)
- Not checked — no full text of the sourcecites [24] Klentzeris LD, 1997, Hum Reprod source
plain- Asserted: passes — The authors put it forward as true.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Among the 102 conceptuses that implanted by the ninth day, 13 percent ended in early loss.”
- Also stated in: § RESULTS · plain
“Early loss was least likely when implantation occurred by the 9th day (13 early losses among 102 pregnancies, or 13 percent)”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > Results
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This proportion rose to 26 percent with implantation on day 10”
- Also stated in: § RESULTS · plain
“rising to 26 percent (14 of 53 pregnancies) when implantation occurred on the 10th day”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > Results
plaincorrelational- Asserted: passes — The authors put it forward as true.
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- Also stated in: § RESULTS · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In our data from natural conception cycles, no conceptus resulting in a clinical pregnancy implanted later than 12 days after ovulation.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
plain- Asserted: passes — The authors put it forward as true.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The mean times of implantation were 9.1 and 9.2 days after ovulation, respectively (P=0.59).”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > RESULTS
plain- Asserted: passes — The authors put it forward as true.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The three pregnancies in which the initial rise in urinary chorionic gonadotropin occurred after day 12 ended in early loss.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > RESULTS
plaincorrelational- Asserted: passes — The authors put it forward as true.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The risk of early pregnancy loss increased with later implantation (P<0.001).”
- Also stated in: § RESULTS · boosted
“The estimated risk of early loss was strongly related to the time of implantation (Fig. 1).”
- Also stated in: § DISCUSSION · boosted
“We found a strong increase in the risk of early pregnancy loss with late implantation, a finding in agreement with data from smaller studies.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > Results
boosteddirect- Asserted: passes — The authors put it forward as true.
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- Also stated in: § RESULTS · boosted
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“to 52 percent on day 11”
- Also stated in: § RESULTS · plain
“52 percent (12 of 23) on the 11th day”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > Results
plaincorrelational- Asserted: passes — The authors put it forward as true.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“and to 82 percent after day 11.”
- Also stated in: § RESULTS · plain
“and 82 percent (9 of 11) with implantation after day 11 (P for trend, <0.001).”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > Results
plaincorrelational- Asserted: passes — The authors put it forward as true.
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In the paper
“The only previous study of the timing of implantation in women with no known fertility problems reported results similar to ours.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
What the sources say
- Not checked — no full text of the sourcecites [26] source
plain- Asserted: passes — The authors put it forward as true.
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- It may state two separate claims as one. 16
- Probably not a substantial claim. 13
- The quote only partly states this claim. 1
The cited sources that could be checked couldn’t confirm or dispute this claim.
In the paper
“The receptivity of the endometrium decreases during the late luteal phase, 1,2 and the corpus luteum is less responsive to chorionic gonadotropin by 11 or 12 days after ovulation.30”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
What the sources say
- Could not verifycites [1] sourceExperimental — accuracy not yet measured
Citation 30 is attached to the corpus-luteum clause, not the endometrial-receptivity clause. In “Preimplantation embryonic signals” (page unavailable), the paper discusses marmoset luteal responses on Days 14 and 20 and says the timing of CG-receptor sensitivity needs clarification. The searched passages do not establish that responsiveness to chorionic gonadotrophin decreases by Day 11 or 12 after ovulation. (LLM, conf=0.72)
- Not checked — no full text of the sourcecites [2] source
- Not checked — no full text of the sourcecites [30] source
plaindirect- Asserted: passes — The authors put it forward as true.
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- Could not verify
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The remaining 189 pregnancies include all 48 that ended in early loss (loss within six weeks after the last menstrual period), all 15 clinical losses (those occurring after six weeks), and 126 pregnancies ending in live birth.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > METHODS
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. It may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“There were 199 conceptions, for 95 per- cent of which (189) we had sufficient data for analysis.”
- Also stated in: § METHODS · plain
“A total of 199 pregnancies were detected by measurement of maternal urinary excretion of chorionic gonadotropin.19 The day of ovulation or implantation could not be determined for 10 pregnancies (5 percent) because of missing data; these pregnancies were excluded from our analysis.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > Results
plainn = 221- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one. The quote only partly states this claim.
- Also stated in: § METHODS · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Among the 126 conceptions that culminated in live birth, the initial rise in urinary chorionic gonadotropin occurred 6 to 12 days after ovulation, with the rise in 106 (84 percent) occurring on day 8, 9, or 10.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > RESULTS
plain- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Of these 189 pregnancies, 141 (75 percent) lasted at least six weeks past the last menstrual period, and the remaining 48 pregnancies (25 percent) ended in early loss.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > Results
plain- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Similarly, in the case of the 15 conceptions that ended in loss more than 6 weeks after the last menstrual period (clinical losses), urinary chorionic gonadotropin was detectable by 7 to 11 days after ovulation, with the rise detected in 12 (80 percent) on day 8, 9, or 10 (Fig. 1).”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > RESULTS
plain- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Among the pregnancies that lasted 6 weeks or more, the first appearance of chorionic gonadotropin occurred 6 to 12 days after ovulation; 118 women (84 percent) had implantation on day 8, 9, or 10.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > Results
plainn = 118- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In contrast, the distribution of implantation times for the 48 pregnancies that ended within 6 weeks after the last menstrual period (early losses) was statistically different (P<0.001); in these pregnancies implantation tended to occur later (mean, 10.5 days), and the times of implantation occurred over a broader range (6 to 18 days) (Fig. 1).”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > RESULTS
plaincorrelational- Asserted: passes — The authors put it forward as true.
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In the paper
“In another report of 76 term pregnancies with in vitro conception, implantation occurred as early as 7 or 8 days after egg retrieval and as late as 13 or 14 days.6”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
What the sources say
- Not checked — no full text of the sourcecites [6] source
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“The day of ovulation or implantation could not be determined for 10 pregnancies (5 percent) because of missing data; these pregnancies were excluded from our analysis.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > METHODS
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
- Rests on an assumption: The 10 pregnancies excluded because of missing data did not differ systematically from the 189 analyzed pregnancies.
In the paper
“In a study of 14 pregnancies ending in live births, rises in serum chorionic gonadotropin were detected as early as 8 days and as late as 12 days after the peak serum concentration of luteinizing hormone.26”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
What the sources say
- Not checked — no full text of the sourcecites [26] source
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“Unhealthy zygotes may develop more slowly, or implantation may be abnormal, 31 resulting in later and weaker production of chorionic gonadotropin.32”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
What the sources say
hedgedconditional- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“There may be opportunities to increase fertility by extending the time during which implantation can occur.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
hedgedconditional- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. It may be too vague to check against evidence.
- Rests on an assumption: The study population of 221 women attempting to conceive after ceasing contraception is representative of healthy women generally, so that findings generalize to most successful human pregnancies.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Specimens were collected on 98 percent of possible woman-days.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > METHODS
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“In one of the largest studies, implantation was reported in relation to egg retrieval for 140 clinical pregnancies in which conception occurred in vitro.27 Implantation was detected 6 to 13 days after egg retrieval.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
What the sources say
- Not checked — no full text of the sourcecites [27] Liu H-C, 1993, Fertil Steril source
plain- Asserted: passes — The authors put it forward as true.
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- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
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It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“We refined this algorithm, validating it against the peak urinary excretion of luteinizing hormone, 13 which corresponds approximately to the day of ovulation.14 Further analysis has suggested that this method is as precise as methods based on the measurement of serum luteinizing hormone.15”
- Also stated in: § DISCUSSION · hedged
“Our measure of ovulation has been validated against the surge in the secretion of luteinizing hormone, which is a standard clinical marker of ovulation, and our marker appears to be as precise as serum luteinizing hormone.15”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > METHODS
What the sources say
- Not checked — no full text of the sourcecites [13] source
- Not matchedcites [14] Collins WP. Biochemical approaches to ovulation prediction and detection and the location of the fertile period in women. In: Jeffcoate SL, ed. Ovulation: methods for its prediction and detection. Vol. 3 of Current topics in reproductive endocrinology. Chichester, England: John Wiley, 1983:49-66.
Couldn’t be matched to a paper in Crossref, so it can’t be checked.
- Not checked — no full text of the sourcecites [15] source
hedged- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
- Also stated in: § DISCUSSION · hedged
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Factors intrinsic to the zygote could also be at work.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
hedgedconditional- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it.
In the paper
“Its production by the conceptus begins early, with expression of messenger RNA reported at the eight-cell stage.25”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
What the sources say
- Not checked — no full text of the sourcecites [25] Bonduelle ML, 1988, Hum Reprod source
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Pregnancies with late-implanting conceptuses may fail for several reasons.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
hedgedconditional- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. It may be too vague to check against evidence.
In the paper
“Our assay for chorionic gonadotropin is sensitive enough to detect low concentrations even among premenopausal women with tubal ligation, 9 so it is likely that the assay is able to detect the initial increase associated with pregnancy.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
What the sources say
- Not checked — no full text of the sourcecites [9] source
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“The data may have implications for efforts to manipulate uterine receptivity.33,34”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
What the sources say
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence.
- Rests on an assumption: The study population of 221 women attempting to conceive after ceasing contraception is representative of healthy women generally, so that findings generalize to most successful human pregnancies.
None of the sources cited for this claim have been checked yet.
In the paper
“Although specific mechanisms of implantation vary widely among species, 22 these three phases of uterine receptivity are also thought to occur in humans. 2”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
What the sources say
- Not checked — no full text of the sourcecites [2] source
- Not checked yetcites [22] Ringler GE, 1990, Curr Opin Obstet Gynecol
hedged- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The abrupt appearance of chorionic gonadotropin and its exponential rise in maternal serum or urine may not mark the very earliest steps in the implantation process, but they do mark the point at which the conceptus has successfully invaded the maternal tissue.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > DISCUSSION
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“The study was approved by the institutional review board of the National Institute of Environmental Health Sciences, and informed consent was obtained from all participants.”
§ The New Eng land Jour nal of Medicine TIME OF IMPLANTATION OF THE CONCEPTUS AND LOSS OF PREGNANCY > METHODS
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
The paper relies on this without support.
The study population of 221 women attempting to conceive after ceasing contraception is representative of healthy women generally, so that findings generalize to most successful human pregnancies.
“We studied 221 couples who had no history of fertility problems and who planned to have children.”
“In our study, the couples had no known fertility problems, and none of the women were being treated with hormones.”
The paper relies on this without support.
The 10 pregnancies excluded because of missing data did not differ systematically from the 189 analyzed pregnancies.
“The day of ovulation or implantation could not be determined for 10 pregnancies (5 percent) because of missing data; these pregnancies were excluded from our analysis.”
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Metadata
- Authors
- Wilcox, A. J., Baird, D. D., & Weinberg, C. R.
- Affiliations
- National Institutes of Health (US)
- Venue
- New England Journal of Medicine
- Publisher
- Massachusetts Medical Society
- Published
- 1999-06-10
- Volume
- 340
- Issue
- 23
- Pages
- 1796-1799
- ISSN
- 0028-4793 (ISSN-L)
- 1533-4406
- OpenAlex
- W2325674170
- Semantic Scholar
- 0f1ee50109d173b320c6525e3e4de2c8a0eee943
- Cited by
- 1,081
- References
- 32
- Citations by year
- 2026: 24 · 2025: 34 · 2024: 74 · 2023: 50 · 2022: 55 · 2021: 60 · 2020: 57 · 2019: 47 · 2018: 37 · 2017: 53 · 2016: 50 · 2015: 29 · 2014: 47 · 2013: 45 · 2012: 54
- FWCI
- 4.04
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- New England Journal of Medicine (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Life Sciences › Immunology and Microbiology › Immunology › Reproductive System and Pregnancy
- Health Sciences › Medicine › Reproductive Medicine › Reproductive Biology and Fertility
- Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Reproductive Health and Contraception
- Keywords
- conceptus implantation, implantation timing, early pregnancy loss, miscarriage, human chorionic gonadotropin, ovulation, luteinization, pregnancy outcomes
- MeSH terms
- Abortion, Spontaneous, Female, Humans, Embryo Implantation, Pregnancy, Risk Factors, Time Factors
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
A language model drew the claims from the paper on 2026-11-08, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).
A second model labelled each claim on 2026-11-08 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).
Cited sources are checked with a language model’s help (gpt-6-sol).
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
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