Table 1 Details of included studies

Fedorcsak et al. 2000 [8] (1996–1998)

Retrospective Cohort study (383 women)

IVF/ICSI

12 patients excluded as incomplete data

< 25.0 (304 women)

≥25.0 (79 women)

Live birth rate

Fertilization rate

No of oocytes retrieved

Abortion rate

Wittemer et al. 2000 [9]

(1997–1998)

Retrospective study

(398 women)

IVF/ICSI

None stated

< 20.0 (87 women)

20.0–25.0 (222 women)

≥ 25.0 (89 women)

Pregnancy rate

Delivery rate

Miscarriage rate

Wang et al. 2000 [10] (1987–1998)

Retrospective study

(3586 women)

IVF/ICSI and GIFT

None stated

< 20.0 (441 women)

20.0–24.9 (1910 women)

25.0–29.9 (814 women)

30.0–34.9 (304 women)

≥35.0 (117 women)

Probability of achieving at least one pregnancy

Loveland et al.

2001 [11]

(1997–1999)

Retrospective study

(139 women / 180 cycles)

IVF

Women > 40 years of age, blastocyst or frozen embryo transfer, donor cycles

≤25 (70 women / 87 cycles)

> 25 (69 women / 93 cycles)

Number of oocytes

Clinical pregnancy rate

Spontaneous abortion

Ongoing pregnancy rate

Wang et al. 2001 [12] (1987–1999)

Cohort study

(1018 women)

IVF/ICSI/GIFT

Women whose BMI or PCOS status was not assessed

< 20.0 (112 women)

20.0–24.9 (509 women)

25.0–29.9 (231 women)

30.0–34.9 (116 women)

≥35.0 (50 women)

Spontaneous abortion

Wang et al. 2002 [13]

(1987–1999)

Retrospective analysis

(2349 women)

IVF/ICSI/GIFT

Ectopic pregnancy, late pregnancy, women whose BMI was measured >/= 1 year before pregnancy

< 18.5 (70 women)

18.5–24.9 (1508 women)

25–29.9 (503 women)

30–34.9 (198 women)

≥35 (70 women)

Spontaneous miscarriage

Winter et al. 2002 [14] (1994–1999)

Cohort

(1123 women / 1196 cycles)

IVF/ICSI/GIFT

< 18.5 (26 women)

18.5–25.0 (701 women)

25.1–30.0 (243 women)

30.1–35.0 (107 women)

> 35.0 (46 women)

Early pregnancy loss

Doody et al.

2003 [15]

(2000–2003)

Retrospective analysis

(822 retrievals)

IVF/ICSI

Donor cycles, age > 40 years

< 25 (460 women)

25–29.9 (194 women)

30–34.9 (89 women)

> 35 (79 women)

Pregnancy rate

Implantation rate

No of oocytes

No of embryos transferred

Ongoing pregnancy rate

Fedorscak et al. 2004 [16]

(1996–2002)

Retrospective Study

(2660 women / 5019 cycles)

IVF/ICSI

None stated

< 18.5 (76 women/136 cycles)

18.5–24.9 (1839 women/3457 cycles)

25.0–29.9 (504 women/963 cycles)

≥30.0 (241 women/463 cycles)

No of oocytes collected

No of embryo transferred

No of embryo transfers

No of biochemical pregnancies

Early pregnancy loss

Miscarriage (6–12 weeks), (> 12 weeks)

Ectopic pregnancy Stillbirth

Live birth rate

Dose of FSH

Duration of FSH

Ryley et al.

2004 [17]

Retrospective study

(6827 cycles)

IVF

Women with BMI > 40

< 20.0 (466 cycles)

20.0–24.9 (3605 cycles)

25.0–29.9 (1632 cycles)

30.0–34.9 (724 cycles)

=35 (400 cycles)

Clinical pregnancy rate

No of oocytes

Van Swieten et al. 2005 [18]

Observational

(162 women/ 288 cycle)

IVF/ICSI

None stated

< 25 (101 women)

25–30 (32 women)

> 30 (29 women)

Fertilisation rate

No oocytes retrieved

Clinical pregnancy rate

Abortion rate

Hammadeh et al. 2005 [19]

Prospective

(52 women)

IVF

None stated

≤25.0 (28 women)

> 25.0 (24 women)

Pregnancy rate

Dechaud et al. 2006 [20]

Prospective study

(573 women/ 789 cycles)

IVF/ICSI

Women with a history of uterine surgery, hydrosalpinges evidenced by ultrasonography, three or more failed attempts at IVF, frozen-thawed cycles, women undergoing pre-implantation diagnosis and those using a protocol other than the long protocol

< 20 (186 women/ 264 cycles)

20–25 (283 women/ 394 cycles)

25–30 (68 women/ 83 cycles)

≥30 (36 women/ 48 cycles)

Duration of ovarian stimulation

Dose of FSH

Implantation rate

No of oocytes

Fertilization rate

Clinical pregnancy rate

Miscarriage rate

Dokras et al.

2006 [21]

(1995–2005)

Retrospective Study

(1293 women)

IVF/IVF with ICSI

Women > 38 years of age, day 2 transfer cycles, cryopreserved embryo transfers, donor oocyte cycle, gamete intrafallopian transfer and zygote intrafallopian transfer cycles

< 25 (683 women)

25–29.9 (295 women)

30.0–39.9 (236 women)

≥40 (79 women)

No of follicles aspirated

Fertilization rate

No of embryo(s) transferred

Clinical pregnancy rate

Miscarriage rate

Delivery rate

Days of stimulation

Mitwally et al. 2006 [22]

Cohort

(183 cycles)

IVF

None stated

< 25.0 (102 cycles)

≥25.0 (81 cycles)

Clinical pregnancy rate

Metwally 2007 [23]

(2001–2006)

Retrospective analysis

(426 women)

IVF/ICSI

Cycles on women whose BMI was unrecorded

19–24.9 (241 women)

25–29.9 (113 women)

≥30 (72 women)

Fertilization rate

Clinical pregnancy rate

Dose of FSH

Duration of FSH

No of oocytes collected

Esinler et al. 2008 [24]

Retrospective Study

(775 women/ 1113 cycles)

ICSI

Freeze-thaw cycles, female age > 40, presence of PCOS, history of irregular menstrual cycle and suspected poor ovarian response

18.5–24.9 (451 women/ 627 cycles)

25.0–29.9 (222 women/ 339 cycles)

≥30.0 (102 women/ 147 cycles)

Clinical pregnancy rate

Fertilization rate

No of miscarriages

No of oocytes

Dose of FSH

Duration of FSH

Martinuzzi et al. 2008 [25]

(2004–2006)

Retrospective study

(417 women)

IVF

Women > 36 years of age, cycle day-3

< 18.5 (21 women)

18.5–24.9 (267 women)

25.0–29.9 (77 women)

≥30 (52 women)

No of oocytes

Fertilization rate

Implantation rate

Clinical pregnancy rate

Ongoing pregnancy rate

Moini et al.

2008 [26]

(2002–2003)

Cross-sectional study

(287 women)

IVF/ICSI

Women who did not have polycystic ovary syndrome, age > 40 years, BMI < 20, women with hypo/hyperthyroidism, hyperprolactinemia and diabetes type 1

20–25 (133 women)

25.1–30 (117 women)

> 30 (37 women)

No of oocytes

No of transferred embryos

Clinical pregnancy rate

Miscarriage rate

Sneed et al.

2008 [27]

(2005–2006)

Retrospective analysis

(1273 women)

IVF

Frozen cycles, donor oocyte or gestational surrogacy cycles, age > 44 years

< 18.5 (28 women)

> 18.5–24.9 (613 women)

> 25–29.9 (325 women)

> 30 (307 women)

No of oocytes

No of embryo transfers

Fertilization rate

Implantation rate

Spontaneous abortion

Clinical pregnancies

Live birth rate

Ozgun et al. 2009 [28]

(2006–2007)

Prospective study

(604 women)

ICSI

Women > 42 years old, medical co-morbidities such as diabetes mellitus, hyper or hypothyroidism, basal FSH > 15 IU/L, thawed embryo transfer cycles, history of prior ovarian surgery, poor responders, couples with more than one etiology for their infertility

< 18.5 (10 women)

18.5–24.9 (232 women)

25–29.9 (229 women)

30–35.9 (111 women)

≥36 (22 women)

No of Pregnancy

Total FSH dosage

Sathya et al.

2010 [29]

Retrospective study

(308 women)

IVF

Women > 40 years of age, FSH > 10 mIU/ml

< 25 (88 women)

25–30 (147 women)

> 30 (73 women)

No of embryos transferred

Clinical pregnancy rate

Missed abortion rate

Multiple pregnancy rate

Ectopic pregnancy rate

Implantation rate

Gonadotrophin dosage

Zhang et al. 2010 [30] (2002–2008)

Retrospective study

(2628 women)

IVF/ICSI

Patients with severe endometriosis (lll and IV stage) diagnosed by laparoscopy, more than two failed previous attempts, preimplantation diagnosis cycles, frozen thawed cycles, protocols other than the long protocol

18.5–24.9 (2222 women)

25.0–29.9 (379 women)

≥30.0 (27 women)

No of oocytes

Fertilization rate

Pregnancy rate

Early pregnancy loss rate

Ectopic pregnancy

Miscarriage rate

Live birth rate

Days of FSH stimulation

Dosage of FSH stimulation

Ongoing pregnancy rate

Bellver et al. 2010 [31]

(2001–2007)

Retrospective study

(6500 cycles)

IVF/ICSI

None stated

< 20 (669 women / 1070 cycles)

20–24.9 (2620 women/ 3930 cycles)

25–29.9 (676 women/ 1081 cycles)

≥ 30 (262 cycles/ 419 cycles)

Total dose of gonadotrophin

No of oocytes

Fertilization rate

No of embryos transferred

Implantation rate

Pregnancy rate

Clinical pregnancy rate

Clinical and global miscarriage rate

Live birth rate

Vilarino et al.

2010 [32]

(2008)

Retrospective

(208 cycles/ 191 women)

IVF/ICSI

Frozen and donor oocyte-derived cycles

< 25 (137 cycles)

≥25 (71 cycles)

Fertilisation rate

No of transferred embryos

Pregnancy rate

Early pregnancy loss

Clinical miscarriage rate

Ectopic pregnancy

Live birth rate

Dosage of FSH

Farhi et al. 2010 [33]

(2006–2007)

Retrospective study

(233 women/ 233 cycles)

IVF

Women ≥38 years of age, other than 2 high-quality embryos, ≥3 previous IVF attempts, women with hydrosalpinx, fibroid uterus, congenital uterine anomaly and chronic illness

≤25.0 (160 women)

> 25.0 (73 women)

Live birth rate

Pregnancy rate

No of oocytes

Fertilization rate

Davies et al. 2010 [34] (2008–2009)

232 cycles

IVF

Donor egg, gestational carrier and pre-implantation genetic diagnosis cycles

< 25.0 (176 cycles)

> 25.0 (56 cycles)

Fetal heartbeat rates

Funabiki et al. 2011 [35] (2006–2010)

Retrospective study

(859 women)

IVF

None stated

< 18.5 (152 women)

18.5–25.0 (648 women)

≥25.0 (59 women)

Pregnancy rate

Ongoing pregnancy rate

Miscarriage rate

No of oocytes

Hill et al. 2011 [36]

Prospective study

(117 women)

IVF

Women > 42 years of age, patients with elevated FSH levels (≥12 mIU/mL)

< 25.0 (58 women)

≥25.0 (59 women)

< 30.0 (96 women)

≥30.0 (21 women)

Live birth rate

Pregnancy rate

Implantation rate

No of oocytes

No of embryo transferred

Days of stimulation

Pinborg et al. 2011 [37]

(2005–2006)

Cohort study

(487 women/ 1417 cycles)

IVF/ ICSI/ FET

Patients undergoing intrauterine insemination cycles, patients with an existing child from fertility treatment, couples who had adopted a child in the 12th month follow-up period and couples who had no treatment during the first 12 months of follow up

< 18.5 (20 women)

18.5–24.9 (305 women)

25.0–29.9 (103 women)

≥30.0 (59 women)

Fertilization rate

No of oocytes

Biochemical pregnancy rate

Ectopic pregnancy rate

Ongoing pregnancy rate

Miscarriage rate

Live birth rate

Dose of gonadotrophin stimulation

Parker et al. 2011 [38]

(2010–2011)

Retrospective study

(995 patients)

IVF/ICSI

None stated

< 18.5 (18 women)

18.5–24.9 (475 women)

25–29.9 (241 women)

> 30 (221 women)

No of oocytes

Clinical pregnancy rate

Implantation rate

Ongoing pregnancy rate

Total FSH dosage

No of embryo transferred

Rittenberg et al. 2011 [39]

(2006–2010)

Cohort Study (413 women)

IVF/ICSI

Women > 40 years, BMI < 18.5, BMI > 35, pre-implantation genetic diagnosis, donor oocyte or embryos frozen for fertility preservation prior to cancer therapy cycles, mullerian duct anomalies, monozygotic twin gestations

18.5–24.9 (192 women)

≥25 (133 women)

Oocyte fertilisation rate

No of oocytes

Clinical pregnancy rate

Live birth rate

Miscarriage rate

Duration of stimulation

Singh et al.

2011 [40]

(2008–2010)

Retrospective Study

(328 women/ 342 cycles)

IVF/ICSI

Women with confounding factors for poor response, endometrial pathologies, hydrosalpinx, ≥3 previous failed attempts, frozen thawed cycles

< 18.5 (26 women)

18.5–24.9 (141 women)

25–29.9 (131 women)

> 30 (18 women)

Fertilisation rate

Pregnancy rate

Total dose of FSH

Total days of stimulation

No of oocytes retrieved

Fertilization rate

Clinical pregnancy rate

Luke et al.

2011 [41]

(2007–2008)

Historical cohort study

(152,500 cycles)

IVF

Women whose height and weight were not recorded, gestational carrier cycles, research or embryo banking with no outcome reported

< 18.5 (4254 cycles)

18.5–24.9 (86,860 cycles)

25–29.9 (35,452 cycles)

30.0–34.9 (15,406 cycles)

35.0–39.9 (6920 cycles)

40.0–44.9 (2513 cycles)

45.0–49.9 (805 cycles)

Pregnancy rate

Fetal death or stillborn

Chavarro et al. 2012 [42]

(2004–2011)

Prospective study

(170 women/ 233 cycles)

IVF/ICSI

Women < 18 and > 45 years of age

< 20 (22 women)

20–22.4 (47 women) 22.5–24.9 (42 women) 25–29.9 (35 women) ≥30 (24 women)

Clinical pregnancy rate Total gonadotrophin dose

Fertilization rate

Clinical pregnancy rate

Live birth rate

Galal et al. 2012 [43]

Prospective cohort

(220 women)

ICSI

None stated

< 25.0 (110 women)

> 25.0 (110 women)

No of oocytes

Fertilization rate

Clinical pregnancy rate

No of embryos transferred

Werner et al. 2012 [44] (2008–2012)

Retrospective study

(355 women)

IVF

None stated

< 18.5 (13 women)

18.5–24.9 (209 women)

25.0–29.9 (88 women)

> 30.0 (45 women)

Pregnancy rate

Clinical implantation rate

Sustained implantation rate

Zander-Fox et al. 2012 [45] (2006–2007)

Retrospective study

(2089 cycles)

IVF/ICSI

Women > 38 years of age, natural and donor cycles

18.5–24.9 (1065 cycles)

25.0–29.9 (486 cycles)

30.0–34.9 (244 cycles)

35.0–39.9 (144 cycles)

≥40.0 (118 cycles)

No of oocytes

Fertilisation rate

Live delivery

Clinical pregnancy

No of oocytes

Ozgun et al. 2012 [46]

(2005–2010)

Retrospective cohort

(935 women)

ICSI

No exclusion criteria

< 18.5 (18 women)

18.5–24.9 (398 women)

25–29.9 (355 women)

≥30 (164 women)

Clinical pregnancy rateNo of oocytes

Miscarriage rate

Total gonadotrophin dose

Ramezanzadeh et al. 2012 [47]

(2010–2011)

Prospective study

(236 women)

IVF

Male factor infertility according to the WHO criteria, presence of systemic disease, age < 18 years or > 40 years and donor oocytes

< 25 (93 women)

25–30 (94 women)

> 30 (49 women)

No of oocytes

Fertilization rate

No of embryo transferred

Biochemical pregnancies

Clinical pregnancy rate

Implantation rate

Moragianni et al. 2012 [48]

(2007–2008)

Retrospective cohort study

(4609 women)

IVF/

IVF-ICSI

Women < 20 years and > 47 years of age, donor oocytes, gestational surrogacy, cryopreserved embryos or those that lacked BMI documentation

< 18.5 (92 women)

18.5–24.99 (2605 women)

25.0–29.99 (1027 women)

30.00–34.99 (477 women)

35.00–39.99 (275 women)

> 40.0 (133 women)

No of oocytes retrieved

Duration of stimulation

Total dosage of gonadotrophin

No of embryo transferred

Implantation

Clinical pregnancy

Biochemical pregnancy

Global miscarriage

Ectopic pregnancy

Live birth

Multiple birth

Bailey et al. 2014 [49]

(2001–2010)

Retrospective Cohort Study (79 women / 101 cycles)

IVF/ICSI

Women < 40 years of age, height and weight measurements > 3 months from the start of cycle, in-vitro maturation,

FSH > 10 mIU/mL, uncontrolled thyroid disease, history of chemotherapy or radiation exposure, recurrent pregnancy loss, uterine factor, balanced translocation in either partner, surgically documented endometriosis or pelvic adhesions, history of pelvic inflammatory disease, adenomyosis and submucosal myoma

18.7–24.9 (51 cycles)

25.0–29.9 (19 cycles)

≥30.0 (31 cycles)

Chemical pregnancy

Miscarriage

Clinical Pregnancy

Live Birth rate

Duration of stimulation of gonadotrophin

Dosage of gonadotrophin

No of oocytes retrieved

Schliep et al.

2014 [50]

(2005–2010)

Prospective Cohort Study (721 women)

IVF/ICSI

Men with non-obstructive azoospermia

< 18.5 (32 women)

18.5–24.9 (407 women)

25–29.9 (147 women)

30–34.9 (72 women)

≥35 (63 women)

Fertilization rate

Pregnancy rate

Live birth rate

Cai et al. 2017 [51]

(2013–2014)

Retrospective Cohort Study

(4401 women / 4798 fresh transfer cycles

IVF/ICSI

Mild stimulation cycles, natural cycles and luteal-phase stimulation cycle, patients with diabetes, glucose intolerance and thyroid abnormality

< 18.5 (886 cycles)

18.5–24.9 (3642 cycles)

≥25 (670 cycles)

Fertilization rate

Live birth rate

Miscarriage rate

Dosage of gonadotrophin

Ozekinci et al. 2015 [52]

(2008–2013)

Retrospective Cohort Study

(298 women)

IVF-ICSI

Underweight women, women > 38 years of age, transfer of > 2 embryos, frozen cycles

18.5–24.9 (164 cycles)

25–29.9 (70 cycles)

≥30 (64 cycles)

Dosage of gonadotrophin

Duration of stimulation

Caillon et al. 2015 [53]

(2006–2009)

Retrospective study

(582 women)

IVF-ICSI

Underweight women

18.5–24.9 (409 women)

≥25 (149 women)

Dosage of gonadotrophin

Implantation rate

Miscarriage rate

Live birth rate

Provost et al. 2016 [54]

2008–2010

Retrospective Cohort Study

(239,127 cycles)

IVF

Women with a height < 48 in. and weight

< 70 pounds

< 18.5 (7149 cycles)

18.5–24.9 (134,588 cycles)

25–29.9 (54,822 cycles)

30–34.9 (24,922 cycles)

35–39.9 (11,747 cycles)

40–44.9 (4084 cycles)

45–49.9 (1292 cycles)

> 50 (463 cycles)

Implantation rate

Clinical pregnancy rate

Miscarriage rate

Live birth rate

Russo et al. 2017 [55]

2010–2014

Retrospective Cohort Study

(520 women)

Not specified

Congenital uterine anomalies, endometrial polyps, intrauterine synechiae, adenomyosis, intra-cavity fibroids, hydrosalpinges, donor cycles, poor quality embryos, cleavage stage embryos, and women > 40 years

< 20 (51 women)

20–24.9 (294 women)

25–29.9 (64 women)

30–39.9 (58 women)

≥40 (54 women)

Miscarriage rate

Clinical pregnancy rate

Live birth rate

Dosage of gonadotrophin

Christensen et al. 2016 [56]

(1999–2009)

Retrospective Cohort Study

(5342 cycles)

IVF/ICSI

Missing information on BMI or treatment type, premature ovulation before oocyte retrieval, intrauterine insemination cycles

< 18.5 (158 cycles)

18.5–24.9 (3539 cycles)

25–29.9 (1171 cycles)

≥30 (474 cycles)

Dosage of gonadotrophin

Clinical pregnancy rate