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Methodological quality graph: review authors' judgements about each methodological quality item presented as percentages across all included studies.
Figuras y tablas -
Figure 1

Methodological quality graph: review authors' judgements about each methodological quality item presented as percentages across all included studies.

Methodological quality summary: review authors' judgements about each methodological quality item for each included study.
Figuras y tablas -
Figure 2

Methodological quality summary: review authors' judgements about each methodological quality item for each included study.

Forest plot of comparison: 1 Live birth rate, outcome: 1.1 Live birth per woman randomised.
Figuras y tablas -
Figure 3

Forest plot of comparison: 1 Live birth rate, outcome: 1.1 Live birth per woman randomised.

Forest plot of comparison: 4 Multiple pregnancy rate, outcome: 4.1 Multiple pregnancy rate per woman randomised.
Figuras y tablas -
Figure 4

Forest plot of comparison: 4 Multiple pregnancy rate, outcome: 4.1 Multiple pregnancy rate per woman randomised.

Forest plot of comparison: 2 Clinical pregnancy, outcome: 2.1 Clinical pregnancy rate per woman randomised.
Figuras y tablas -
Figure 5

Forest plot of comparison: 2 Clinical pregnancy, outcome: 2.1 Clinical pregnancy rate per woman randomised.

Forest plot of comparison: 3 Miscarriage rate, outcome: 3.1 Miscarriage per woman randomised.
Figuras y tablas -
Figure 6

Forest plot of comparison: 3 Miscarriage rate, outcome: 3.1 Miscarriage per woman randomised.

Forest plot of comparison: 5 Monozygotic twinning rate, outcome: 5.1 Monozygotic twinning per woman randomised.
Figuras y tablas -
Figure 7

Forest plot of comparison: 5 Monozygotic twinning rate, outcome: 5.1 Monozygotic twinning per woman randomised.

Comparison 1 Live birth: Assisted hatching compared with no assisted hatching, Outcome 1 Live birth per woman randomised.
Figuras y tablas -
Analysis 1.1

Comparison 1 Live birth: Assisted hatching compared with no assisted hatching, Outcome 1 Live birth per woman randomised.

Comparison 1 Live birth: Assisted hatching compared with no assisted hatching, Outcome 2 First or repeat attempt.
Figuras y tablas -
Analysis 1.2

Comparison 1 Live birth: Assisted hatching compared with no assisted hatching, Outcome 2 First or repeat attempt.

Comparison 1 Live birth: Assisted hatching compared with no assisted hatching, Outcome 3 Conception mode.
Figuras y tablas -
Analysis 1.3

Comparison 1 Live birth: Assisted hatching compared with no assisted hatching, Outcome 3 Conception mode.

Comparison 1 Live birth: Assisted hatching compared with no assisted hatching, Outcome 4 Hatching method.
Figuras y tablas -
Analysis 1.4

Comparison 1 Live birth: Assisted hatching compared with no assisted hatching, Outcome 4 Hatching method.

Comparison 1 Live birth: Assisted hatching compared with no assisted hatching, Outcome 5 Prognosis.
Figuras y tablas -
Analysis 1.5

Comparison 1 Live birth: Assisted hatching compared with no assisted hatching, Outcome 5 Prognosis.

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 1 Multiple pregnancy rate per woman randomised.
Figuras y tablas -
Analysis 2.1

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 1 Multiple pregnancy rate per woman randomised.

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 2 First or repeat attempt.
Figuras y tablas -
Analysis 2.2

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 2 First or repeat attempt.

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 3 Conception mode.
Figuras y tablas -
Analysis 2.3

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 3 Conception mode.

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 4 Hatching method.
Figuras y tablas -
Analysis 2.4

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 4 Hatching method.

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 5 Prognosis.
Figuras y tablas -
Analysis 2.5

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 5 Prognosis.

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 6 Multiple pregnancy rate per woman grouped by extent of assisted hatching.
Figuras y tablas -
Analysis 2.6

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 6 Multiple pregnancy rate per woman grouped by extent of assisted hatching.

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 7 Multiple pregnancy per pregnancy.
Figuras y tablas -
Analysis 2.7

Comparison 2 Multiple pregnancy: Assisted hatching compared with no assisted hatching, Outcome 7 Multiple pregnancy per pregnancy.

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 1 Clinical pregnancy rate per woman randomised.
Figuras y tablas -
Analysis 3.1

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 1 Clinical pregnancy rate per woman randomised.

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 2 First or repeat attempt.
Figuras y tablas -
Analysis 3.2

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 2 First or repeat attempt.

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 3 Conception mode.
Figuras y tablas -
Analysis 3.3

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 3 Conception mode.

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 4 Hatching method.
Figuras y tablas -
Analysis 3.4

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 4 Hatching method.

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 5 Prognosis.
Figuras y tablas -
Analysis 3.5

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 5 Prognosis.

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 6 Extent of assisted hatching.
Figuras y tablas -
Analysis 3.6

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 6 Extent of assisted hatching.

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 7 Fresh and frozen embryo transfer.
Figuras y tablas -
Analysis 3.7

Comparison 3 Clinical pregnancy: Assisted hatching compared with no assisted hatching, Outcome 7 Fresh and frozen embryo transfer.

Comparison 4 Clinical pregnancies in trials which reported live births: Assisted hatching compared with no assisted hatching, Outcome 1 Clinical Pregnancies in trials reporting live births.
Figuras y tablas -
Analysis 4.1

Comparison 4 Clinical pregnancies in trials which reported live births: Assisted hatching compared with no assisted hatching, Outcome 1 Clinical Pregnancies in trials reporting live births.

Comparison 5 Miscarriage: Assisted hatching compared with no assisted hatching, Outcome 1 Miscarriage per woman randomised.
Figuras y tablas -
Analysis 5.1

Comparison 5 Miscarriage: Assisted hatching compared with no assisted hatching, Outcome 1 Miscarriage per woman randomised.

Comparison 5 Miscarriage: Assisted hatching compared with no assisted hatching, Outcome 2 First or repeat attempt.
Figuras y tablas -
Analysis 5.2

Comparison 5 Miscarriage: Assisted hatching compared with no assisted hatching, Outcome 2 First or repeat attempt.

Comparison 5 Miscarriage: Assisted hatching compared with no assisted hatching, Outcome 3 Conception mode.
Figuras y tablas -
Analysis 5.3

Comparison 5 Miscarriage: Assisted hatching compared with no assisted hatching, Outcome 3 Conception mode.

Comparison 5 Miscarriage: Assisted hatching compared with no assisted hatching, Outcome 4 Hatching method.
Figuras y tablas -
Analysis 5.4

Comparison 5 Miscarriage: Assisted hatching compared with no assisted hatching, Outcome 4 Hatching method.

Comparison 5 Miscarriage: Assisted hatching compared with no assisted hatching, Outcome 5 Prognosis.
Figuras y tablas -
Analysis 5.5

Comparison 5 Miscarriage: Assisted hatching compared with no assisted hatching, Outcome 5 Prognosis.

Comparison 5 Miscarriage: Assisted hatching compared with no assisted hatching, Outcome 6 Miscarriage per clinical pregnancy.
Figuras y tablas -
Analysis 5.6

Comparison 5 Miscarriage: Assisted hatching compared with no assisted hatching, Outcome 6 Miscarriage per clinical pregnancy.

Comparison 6 Monozygotic twinning: Assisted hatching compared with no assisted hatching, Outcome 1 Monozygotic twinning per woman randomised.
Figuras y tablas -
Analysis 6.1

Comparison 6 Monozygotic twinning: Assisted hatching compared with no assisted hatching, Outcome 1 Monozygotic twinning per woman randomised.

Comparison 7 Robust studies (randomisation method and allocation concealment stated & live birth reported): Assisted hatching compared with no assisted hatching, Outcome 1 Live Births.
Figuras y tablas -
Analysis 7.1

Comparison 7 Robust studies (randomisation method and allocation concealment stated & live birth reported): Assisted hatching compared with no assisted hatching, Outcome 1 Live Births.

Comparison 7 Robust studies (randomisation method and allocation concealment stated & live birth reported): Assisted hatching compared with no assisted hatching, Outcome 2 Clinical Pregnancies.
Figuras y tablas -
Analysis 7.2

Comparison 7 Robust studies (randomisation method and allocation concealment stated & live birth reported): Assisted hatching compared with no assisted hatching, Outcome 2 Clinical Pregnancies.

Summary of findings for the main comparison. Live birth

Live birth

Patient or population: Women undergoing assisted conception
Intervention: Assisted hatching compared with no assisted hatching

Outcomes

Illustrative comparative risks* (95% CI)

Relative effect
(95% CI)

No of Participants
(studies)

Quality of the evidence
(GRADE)

Comments

Assumed risk

Corresponding risk

Control

Assisted hatching

Live birth per woman randomised

305 per 1000

311 per 1000
(271 to 356)

OR 1.03
(0.85 to 1.26)

1921
(9 studies)

⊕⊕⊕⊝
moderate1

*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CI: Confidence interval; OR: Odds ratio;

GRADE Working Group grades of evidence
High quality: Further research is very unlikely to change our confidence in the estimate of effect.
Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Very low quality: We are very uncertain about the estimate.

1 Many of the trials had some methodological limitations or missing information

Figuras y tablas -
Summary of findings for the main comparison. Live birth
Summary of findings 2. Multiple pregnancy

Multiple pregnancy

Patient or population: Women undergoing assisted reproduction
Intervention: Assisted hatching compared with no assisted hatching

Outcomes

Illustrative comparative risks* (95% CI)

Relative effect
(95% CI)

No of Participants
(studies)

Quality of the evidence
(GRADE)

Comments

Assumed risk

Corresponding risk

Control

Assisted hatching

Multiple pregnancy rate per woman randomised

102 per 1000

136 per 1000
(112 to 162)

OR 1.38
(1.11 to 1.7)

3447
(14 studies)

⊕⊕⊝⊝
low1,2

*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CI: Confidence interval; OR: Odds ratio;

GRADE Working Group grades of evidence
High quality: Further research is very unlikely to change our confidence in the estimate of effect.
Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Very low quality: We are very uncertain about the estimate.

1 There was methodological limitations or missing information in most trials
2 I square statistic was 57%

Figuras y tablas -
Summary of findings 2. Multiple pregnancy
Summary of findings 3. Clinical pregnancy

Clinical pregnancy

Patient or population: Women undergoing assisted reproduction
Intervention: Assisted hatching compared with no assisted hatching

Outcomes

Illustrative comparative risks* (95% CI)

Relative effect
(95% CI)

No of Participants
(studies)

Quality of the evidence
(GRADE)

Comments

Assumed risk

Corresponding risk

Control

Assisted hatching

Clinical pregnancy rate per woman randomised

332 per 1000

360 per 1000
(334 to 387)

OR 1.13
(1.01 to 1.27)

5728
(31 studies)

⊕⊕⊕⊝
moderate1

*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CI: Confidence interval; OR: Odds ratio;

GRADE Working Group grades of evidence
High quality: Further research is very unlikely to change our confidence in the estimate of effect.
Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Very low quality: We are very uncertain about the estimate.

1 There were methodological limitations or missing information in most of the trials

Figuras y tablas -
Summary of findings 3. Clinical pregnancy
Summary of findings 4. Miscarriage

Miscarriage

Patient or population: Women undergoing assisted reproduction
Intervention: Assisted hatching compared with no assisted hatching

Outcomes

Illustrative comparative risks* (95% CI)

Relative effect
(95% CI)

No of Participants
(studies)

Quality of the evidence
(GRADE)

Comments

Assumed risk

Corresponding risk

Control

Miscarriage

Miscarriage per woman randomised

45 per 1000

46 per 1000
(32 to 68)

OR 1.03
(0.69 to 1.54)

2131
(14 studies)

⊕⊕⊕⊝
moderate1

*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CI: Confidence interval; OR: Odds ratio;

GRADE Working Group grades of evidence
High quality: Further research is very unlikely to change our confidence in the estimate of effect.
Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Very low quality: We are very uncertain about the estimate.

1 There were methodological limitations or missing information in most of the trials

Figuras y tablas -
Summary of findings 4. Miscarriage
Table 1. Mean age of participants in assisted hatching and control groups

Study

AH n, mean age (SD)

Control n, mean age (SD)

OR for clinical pregnancy

Antinori 1999: First IVF

73, 37.5

69, 36.0

1.27 (0.70, 2.32)

Antinori 1999: Repeat IVF

96, 27.5

103, 27

1.86 (0.81, 4.25)

Balaban 2006

183, 32.4 (3.3)

183, 32.7 (3.1)

1.85 (1.19 to 2.86)

Balakier 2009

45, 32.5 (3.8)

39, 33.8 (3.2)

0.64 (0.27 to 1.55)

Ciray 2005

60, 33.1 (4.2)

30, 34.0 (3.7)

0.62 (0.26 to 1.49)

Baruffi 2000

51, 31.8 (3.6)

52, 31.4 (3.6)

0.74 (0.33 to 1.65)

Carter 2003

121, 34 (3.3)

82, 34 (3.2)

0.95 (0.54 to 1.67)

Cohen 1992 FSH <15

69, 36.50 (3.30)

68, 36.70 (3.70)

2.11 (1.18 to 3.77)

Cohen 1992 poor prognosis

80, 36.7 (4.3)

83, 35.3 (4.2)

1.30 (0.66 to 2.55)

Cohen 1992 FSH > 15

not stated

not stated

1.30 (0.66 to 2.55)

Fang 2010

61, 32.3 (3.4)

64, 32.1 (3.6)

2.37 (1.07 to 5.28)

Ge 2008 fresh embryo

387, 31.08 (4.68)

373, 30.44 (4.15)

0.99 (0.74 to 1.32)

Ge 2008 frozen embryo

100, 31.84 (3.85)

100, 30.66 (4.42)

2.05 (0.99 to 4.22)

Germond 2004 first cycle of frozen‐thawed embryos

62, 32.8 (4.2)

53, 32.6 (3.8)

0.09 (0.01 to 0.76)

Germond 2004 poor prognosis, first cycle of fresh embryos

22, 39.3 (2.9)

21, 38.3 (3.4)

0.51 (0.10 to 2.45)

Hagemann 2010

59, 32.1 (3.0)

62, 31.2 (3.5)

0.81 (0.37 to 1.76)

Hellebaut 1996

60, 30.9 (4.3)

60, 30.8 (3.9)

1.15 (0.55 to 2.43)

Hurst 1998

13, 30.0 (0.9)

7, 30.0 (0.8)

0.40 (0.06 to 2.89)

Isik 2000

24, 30.5 (5.2)

22, 29.1 (3.6)

2.0 (0.62 to 6.49)

Jelinkova 2002

128, 32.3 (4.24)

129, 32.1 (3.16)

1.86 (1.12 to 3.10)

Kutlu 2010: Good prognosis

73, 29.9 (2.9)

66, 28.9 (3.4)

1.06 (0.54, 2.08)

Kutlu 2010:Poor prognosis

58, 38.0 (2.3)

55, 37.4 (2.4)

1.23 (0.58, 2.60)

Lanzendorf 1998

41, 38.30 (0.31)

48, 38.50 (0.26)

0.90 (0.38 to 2.10)

Mansour 2000

30, 37.30 (5.60)

41, 36.30 (5.20)

3.86 (0.91 to 16.41)

Nagy 1999

20, 32.0 (4.0)

20, 31.4 (3.7)

8.0 (1.44 to 44.3)

Ng 2005

80, 34.0 (range: 25 to 40)

80, 34.0 (range: 26 to 40)

0.81 (0.33 to 2.00)

Petersen 2005 one previous implantation failure

35, 34.6 (4.6)

35, 34.1 (5.3)

1.15 (0.41 to 3.19)

Petersen 2005 several previous implanatation failures

40, 35.7 (3.8)

40, 35.3 (5.1)

4.11 (1.04 to 16.29)

Sagoskin 2007

118, 34.0 (3.3)

81, 34.0 (3.2)

0.94 (0.53 to1.65)

Tucker 1993

110, 34.1 (4.8)

108, 34.2 (4.1)

1.37 (0.79 to 2.35)

Tucker 1996

50, 35.3 (4.2)

50, 33.5 (4.3)

0.74 (0.35 to 1.59

Valojerdi 2010

200, 30.86 (5.82)

200, 29.85 (5.14)

0.53 (0.35 to 0.80)

Figuras y tablas -
Table 1. Mean age of participants in assisted hatching and control groups
Table 2. Prognostic factors in included trials

Study ID

Balanced age between groups

Balances no. of embryos transferred

Prognosis: poor/good

FSH levels

Blastocyst transfer

Complete/partial AH

Frozen cycles

Antinori 1999

AH mean 1.5 years older

Yes

Good and Poor subgroups

No data

No

Complete hole

Not stated

Balaban 2006

Yes

Yes

Unselected

< 10

No

Thinning

Frozen

Balakier 2009

AH mean 1.3 years older

Yes

Good

< 10

No

Thinning

Fresh

Baruffi 2000

Yes

Yes

Good

No data

No

Thinning

Fresh

Carter 2003

Yes

Yes

Good

< 10

No

Not stated

Fresh

Ciray 2005

Yes

Yes

Good

< 15

No

Thinning

Fresh

Cohen 1992

Yes

Yes

Unstated

<= 15, and > 15 subgroups

No

Complete hole

Fresh

Elhelw 2005

Yes

No data

Poor

No data

No

Thinning

Frozen

Fang 2010

Yes

Yes

Not stated

No data

No

Mechanical expansion

Frozen thawed

Ge 2008

Yes

Yes

Mixed

No data

No

Thinning

Fresh and Frozen Subgroups

Germond 2004

Yes

Yes

Mixed, in subgroups

between 3 and 12

No

Complete hole

Fresh and frozen, in subgroups

Hagemann 2010

Mean age data only given for combined cycles 1 and 2

Yes

under 38 years, >2 previous failed cycles, ZP thickness >13micrometers

No data

No

20micrometer diameter opening

Fresh

Hellebaut 1996

Yes

Yes

Good

No data

No

Complete hole

Fresh

Hurst 1998

Yes

Yes

Good

< 10

No

Complete hole

Fresh

Isik 2000

AH mean 1.4 years older

Yes

Unstated

< 10

Yes

Removal complete

Fresh

Isiklar 1999

No data

Yes

Unstated

No data

Yes

Complete hole

Fresh

Jelinkova 2002

Yes

Yes

Poor

No data

Yes

Removal complete

Fresh

Kutlu 2010

Yes

Yes

Good and Poor Subgroups

No data

No

Complete hole

Fresh

Laffoon 1999

No data

No data

Good

No data

No

Complete hole

Fresh

Lanzendorf 1998

No

Yes

Poor

No data

No

Complete hole

Fresh

Nagy 1999

Yes

Yes

Unstated

No data

No

Thinning

Frozen‐thaw cycles

Ng 2005

Yes

Higher proportion of controls received 3 embryos

Unstated

< 11

No

Thinning

Frozen‐thaw cycles

Petersen 2005

Yes

Yes

Poor

No data

No

Thinning

Fresh

Rufas‐Sapir 2004

No data

Yes

Poor

No data

No

Complete hole

Fresh

Ryan 1997

No data

No data

Unstated

No data

No

Complete hole

Both

Sagoskin 2007

Yes

Yes

Good

< 10

No

Hole

Fresh

Stein 1995

No data

No data

Poor

No data

No

Complete hole

Fresh

Tucker 1993

Yes

Yes

Good

< 15

No

Thinning

Fresh

Tucker 1996

AH mean 1.8 years older

Yes

Not stated

No data

No

Complete hole

Fresh

Valojerdi 2010

Yes

Yes

Not stated

No data

No

Partially thinned

Vitrified‐warmed embryo

AH = assisted hatching
ET = embryo transfer
FSH = follicle‐stimulating hormone

Figuras y tablas -
Table 2. Prognostic factors in included trials
Comparison 1. Live birth: Assisted hatching compared with no assisted hatching

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Live birth per woman randomised Show forest plot

9

1921

Odds Ratio (M‐H, Fixed, 95% CI)

1.03 [0.85, 1.26]

2 First or repeat attempt Show forest plot

2

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

2.1 First attempt at IVF or ICSI

1

20

Odds Ratio (M‐H, Fixed, 95% CI)

0.24 [0.03, 2.03]

2.2 Repeat attempt at IVF or ICSI

1

150

Odds Ratio (M‐H, Fixed, 95% CI)

1.40 [0.62, 3.13]

3 Conception mode Show forest plot

4

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

3.1 ICSI only

1

150

Odds Ratio (M‐H, Fixed, 95% CI)

1.40 [0.62, 3.13]

3.2 IVF only

3

241

Odds Ratio (M‐H, Fixed, 95% CI)

1.00 [0.60, 1.68]

4 Hatching method Show forest plot

9

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

4.1 Chemical

4

366

Odds Ratio (M‐H, Fixed, 95% CI)

1.13 [0.74, 1.74]

4.2 Laser

5

1555

Odds Ratio (M‐H, Fixed, 95% CI)

1.01 [0.81, 1.26]

5 Prognosis Show forest plot

8

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

5.1 Poor prognosis

4

576

Odds Ratio (M‐H, Fixed, 95% CI)

1.46 [0.99, 2.15]

5.2 Good prognosis

5

1187

Odds Ratio (M‐H, Fixed, 95% CI)

0.94 [0.74, 1.19]

Figuras y tablas -
Comparison 1. Live birth: Assisted hatching compared with no assisted hatching
Comparison 2. Multiple pregnancy: Assisted hatching compared with no assisted hatching

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Multiple pregnancy rate per woman randomised Show forest plot

14

3447

Odds Ratio (M‐H, Fixed, 95% CI)

1.38 [1.11, 1.70]

2 First or repeat attempt Show forest plot

5

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

2.1 First attempt at IVF or ICSI

2

294

Odds Ratio (M‐H, Fixed, 95% CI)

0.62 [0.12, 3.19]

2.2 Repeat attempt at IVF or ICSI

4

765

Odds Ratio (M‐H, Fixed, 95% CI)

1.12 [0.70, 1.80]

3 Conception mode Show forest plot

8

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

3.1 ICSI only

2

391

Odds Ratio (M‐H, Fixed, 95% CI)

3.54 [1.70, 7.39]

3.2 IVF only

6

1126

Odds Ratio (M‐H, Fixed, 95% CI)

1.87 [1.28, 2.72]

4 Hatching method Show forest plot

14

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

4.1 Chemical

4

534

Odds Ratio (M‐H, Fixed, 95% CI)

1.55 [0.98, 2.47]

4.2 Laser

9

2869

Odds Ratio (M‐H, Fixed, 95% CI)

1.27 [1.00, 1.61]

4.3 Mechanical

1

44

Odds Ratio (M‐H, Fixed, 95% CI)

8.33 [1.56, 44.64]

5 Prognosis Show forest plot

9

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

5.1 Poor prognosis

5

883

Odds Ratio (M‐H, Fixed, 95% CI)

1.88 [1.19, 2.96]

5.2 Good prognosis

6

1569

Odds Ratio (M‐H, Fixed, 95% CI)

1.08 [0.81, 1.44]

6 Multiple pregnancy rate per woman grouped by extent of assisted hatching Show forest plot

13

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

6.1 Thinning only

5

1970

Odds Ratio (M‐H, Fixed, 95% CI)

1.39 [1.05, 1.84]

6.2 Breach by hole

7

1249

Odds Ratio (M‐H, Fixed, 95% CI)

1.51 [1.05, 2.17]

6.3 Complete removal of zona

1

25

Odds Ratio (M‐H, Fixed, 95% CI)

0.62 [0.07, 5.28]

7 Multiple pregnancy per pregnancy Show forest plot

14

1383

Odds Ratio (M‐H, Fixed, 95% CI)

1.39 [1.09, 1.77]

Figuras y tablas -
Comparison 2. Multiple pregnancy: Assisted hatching compared with no assisted hatching
Comparison 3. Clinical pregnancy: Assisted hatching compared with no assisted hatching

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Clinical pregnancy rate per woman randomised Show forest plot

31

5728

Odds Ratio (M‐H, Fixed, 95% CI)

1.13 [1.01, 1.27]

2 First or repeat attempt Show forest plot

14

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

2.1 First attempt at IVF or ICSI

6

650

Odds Ratio (M‐H, Fixed, 95% CI)

0.77 [0.54, 1.10]

2.2 Repeat attempt at IVF or ICSI

9

1365

Odds Ratio (M‐H, Fixed, 95% CI)

1.42 [1.11, 1.81]

3 Conception mode Show forest plot

22

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

3.1 ICSI only

8

1205

Odds Ratio (M‐H, Fixed, 95% CI)

1.34 [1.05, 1.71]

3.2 IVF only

14

2300

Odds Ratio (M‐H, Fixed, 95% CI)

1.29 [1.08, 1.54]

4 Hatching method Show forest plot

31

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

4.1 Chemical

11

1536

Odds Ratio (M‐H, Fixed, 95% CI)

1.33 [1.08, 1.64]

4.2 Laser

15

3606

Odds Ratio (M‐H, Fixed, 95% CI)

1.04 [0.90, 1.19]

4.3 Mechanical

5

586

Odds Ratio (M‐H, Fixed, 95% CI)

1.30 [0.89, 1.88]

5 Prognosis Show forest plot

20

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

5.1 Poor prognosis

12

1675

Odds Ratio (M‐H, Fixed, 95% CI)

1.49 [1.19, 1.85]

5.2 Good prognosis

12

2253

Odds Ratio (M‐H, Fixed, 95% CI)

1.02 [0.86, 1.21]

6 Extent of assisted hatching Show forest plot

30

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

6.1 Thinning only

12

2936

Odds Ratio (M‐H, Fixed, 95% CI)

1.05 [0.90, 1.23]

6.2 Breach by hole only

15

2163

Odds Ratio (M‐H, Fixed, 95% CI)

1.14 [0.94, 1.37]

6.3 Complete removal of zona

2

301

Odds Ratio (M‐H, Fixed, 95% CI)

1.93 [1.21, 3.09]

6.4 Expansion of zona pellucida

1

125

Odds Ratio (M‐H, Fixed, 95% CI)

2.37 [1.07, 5.28]

7 Fresh and frozen embryo transfer Show forest plot

30

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

7.1 Fresh embryo transfer

24

4050

Odds Ratio (M‐H, Fixed, 95% CI)

1.14 [1.01, 1.30]

7.2 Frozen embryo transfer only

8

1478

Odds Ratio (M‐H, Fixed, 95% CI)

1.14 [0.90, 1.44]

Figuras y tablas -
Comparison 3. Clinical pregnancy: Assisted hatching compared with no assisted hatching
Comparison 4. Clinical pregnancies in trials which reported live births: Assisted hatching compared with no assisted hatching

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Clinical Pregnancies in trials reporting live births Show forest plot

9

1921

Odds Ratio (M‐H, Fixed, 95% CI)

1.03 [0.85, 1.25]

Figuras y tablas -
Comparison 4. Clinical pregnancies in trials which reported live births: Assisted hatching compared with no assisted hatching
Comparison 5. Miscarriage: Assisted hatching compared with no assisted hatching

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Miscarriage per woman randomised Show forest plot

14

2131

Odds Ratio (M‐H, Fixed, 95% CI)

1.03 [0.69, 1.54]

2 First or repeat attempt Show forest plot

6

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

2.1 First attempt at IVF or ICSI

3

264

Odds Ratio (M‐H, Fixed, 95% CI)

0.91 [0.29, 2.80]

2.2 Repeat attempt at IVF or ICSI cycle

4

663

Odds Ratio (M‐H, Fixed, 95% CI)

2.14 [0.72, 6.35]

3 Conception mode Show forest plot

10

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

3.1 ICSI only

4

665

Odds Ratio (M‐H, Fixed, 95% CI)

1.20 [0.58, 2.47]

3.2 IVF only

6

896

Odds Ratio (M‐H, Fixed, 95% CI)

1.28 [0.65, 2.52]

4 Hatching method Show forest plot

14

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

4.1 Chemical

5

412

Odds Ratio (M‐H, Fixed, 95% CI)

1.11 [0.56, 2.21]

4.2 Laser

8

1565

Odds Ratio (M‐H, Fixed, 95% CI)

0.98 [0.59, 1.63]

4.3 Mechanical

1

154

Odds Ratio (M‐H, Fixed, 95% CI)

1.14 [0.07, 18.58]

5 Prognosis Show forest plot

10

Odds Ratio (M‐H, Fixed, 95% CI)

Subtotals only

5.1 Poor prognosis

6

830

Odds Ratio (M‐H, Fixed, 95% CI)

1.06 [0.57, 1.99]

5.2 Good prognosis

5

626

Odds Ratio (M‐H, Fixed, 95% CI)

1.03 [0.50, 2.14]

6 Miscarriage per clinical pregnancy Show forest plot

14

687

Odds Ratio (M‐H, Random, 95% CI)

0.96 [0.62, 1.50]

Figuras y tablas -
Comparison 5. Miscarriage: Assisted hatching compared with no assisted hatching
Comparison 6. Monozygotic twinning: Assisted hatching compared with no assisted hatching

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Monozygotic twinning per woman randomised Show forest plot

6

729

Odds Ratio (M‐H, Fixed, 95% CI)

3.23 [0.34, 31.03]

Figuras y tablas -
Comparison 6. Monozygotic twinning: Assisted hatching compared with no assisted hatching
Comparison 7. Robust studies (randomisation method and allocation concealment stated & live birth reported): Assisted hatching compared with no assisted hatching

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1 Live Births Show forest plot

1

960

Odds Ratio (M‐H, Fixed, 95% CI)

1.08 [0.82, 1.41]

2 Clinical Pregnancies Show forest plot

1

960

Odds Ratio (M‐H, Fixed, 95% CI)

1.10 [0.85, 1.43]

Figuras y tablas -
Comparison 7. Robust studies (randomisation method and allocation concealment stated & live birth reported): Assisted hatching compared with no assisted hatching