Background
Methods
The cohort study
Review of literature and meta-analysis
Results
The cohort study
Number (%) of births | Placenta Previa Rate | Unadjusted OR (95% CI)** | Adjusted OR (95% CI)** | |
---|---|---|---|---|
Previous cesarean delivery
|
p < 0.001
|
p < 0.001
| ||
Yes | 86055 (21.5) | 8.7 | 1.88 (1.71-2.07) | 1.60 (1.44-1.76) |
No | 313619 (78.5) | 4.4 | - | - |
Previous placenta previa
|
p < 0.001
|
p < 0.001
| ||
Yes | 1429 (0.4) | 43.4 | 7.74 (5.80-10.34) | 4.77 (3.55-6.42) |
No | 398245 (99.6) | 5.2 | - | - |
Maternal age*
|
p < 0.001
|
p < 0.001
| ||
<20 | 15393 (3.9) | 1.9 | 0.56 (0.38-0.82) | 0.58 (0.39-0.86) |
20-29 | 191151 (47.8) | 3.6 | - | - |
30-39 | 184237 (46.1) | 7.1 | 2.01 (1.82-2.22) | 1.83 (1.65-2.05) |
≥40 | 8887 (2.2) | 13.2 | 3.60 (2.90-4.46) | 3.01 (2.41-3.75) |
Ethnicity*
|
p = 0.053
|
p = 0.387
| ||
White | 275181 (80.4) | 5.6 | - | - |
Asian | 42486 (12.4) | 4.8 | 0.86 (0.74-0.99) | 1.03 (0.89-1.21) |
Black | 12158 (3.6) | 5.0 | 0.91 (0.70-1.17) | 0.96 (0.74-1.25) |
Other | 12448 (3.6) | 6.7 | 1.19 (0.96-1.50) | 1.22 (0.97-1.52) |
Deprivation*
|
p < 0.001
|
p = 0.180
| ||
Q1 Most deprived | 122039 (30.6) | 4.0 | - | - |
Q2 | 90740 (22.8) | 5.1 | 1.30 (1.14-1.49) | 1.10 (0.96-1.26) |
Q3 | 85913 (21.6) | 6.1 | 1.52 (1.33-1.73) | 1.15 (0.99-1.32) |
Q4 Least deprived | 99403 (25.0) | 6.5 | 1.63 (1.44-1.85) | 1.16 (1.01-1.33) |
Pre-existing hypertension
|
p = 0.080
|
p = 0.026
| ||
Yes | 5730 (1.4) | 3.5 | 0.69 (0.44-1.08) | 0.62 (0.39-0.98) |
No | 393944 (98.6) | 5.4 | - | - |
Gestational hypertension***
|
p = 0.322
|
p = 0.098
| ||
Yes | 8464 (2.1) | 5.1 | 0.85 (0.60-1.19) | 0.76 (0.54-1.07) |
No | 391210 (97.9) | 5.3 | - | - |
Gestational diabetes
|
p = 0.337
|
p = 0.892
| ||
Yes | 5586 (1.4) | 5.9 | 1.19 (0.84-1.69) | 0.98 (0.69-1.39) |
No | 394088 (98.6) | 5.3 | - | - |
Polyhydramnios
|
p = 0.003
|
p = 0.009
| ||
Yes | 1985 (0.5) | 11.1 | 2.11 (1.35-3.28) | 1.92 (1.23-3.00) |
No | 397689 (99.5) | 5.3 | - | - |
Inter-birth interval
|
p < 0.001
|
p < 0.001
| ||
<1 | 7511 (1.9) | 6.4 | 1.38 (1.02-1.87) | 2.08 (1.53-2.83) |
1 to 2 | 120803 (30.2) | 4.8 | 0.92 (0.81-1.03) | 1.01 (0.90-1.14) |
2 to 3 | 133834 (33.5) | 5.2 | - | - |
3 to 4 | 73992 (18.5) | 5.5 | 1.08 (0.95-1.23) | 1.08 (0.94-1.23) |
4 to 5 | 35557 (8.9) | 6.1 | 1.19 (1.01-1.40) | 1.19 (1.01-1.40) |
≥5 | 27977 (7.0) | 6.6 | 1.29 (1.09-1.53) | 1.32 (1.11-1.57) |
Review of literature and meta-analysis
Study ID | Country | Study period | Study design | Population | Size | First two births | Risk adjustment* |
---|---|---|---|---|---|---|---|
Singh_1981 | India | 1973-1978 | Cohort | Hospital | 12040 | 0 | - |
Gorodeski_1985 | Israel | 1972-1983 | Case-control | Hospital | 455 | 0 | - |
Sauer_1985 | USA | 1981-1984 | Case-control | Hospital | 135 | 0 | - |
Clark_1985 | USA | 1977-1983 | Cohort | Hospital | 97799 | 0 | - |
Rose_1986 | England | 1978-1982 | Case-control | Hospital | 160 | 0 | AP; |
Hemminki_1987 | Sweden | Cohort | Population | 7337 | 1 | AP; | |
Nielsen_1989 | Sweden | 1978-1987 | Cohort | Hospital | 24644 | 0 | - |
Williams_1991 | USA | 1977-1980 | Case-control | Hospital | 12420 | 0 | AP; abortion; alcohol and tobacco use; SE |
Chattopadhyay_1993 | Saudi Arabia | 1988-1992 | Cohort | Hospital | 41206 | 0 | - |
Zhang_1993 | USA | 1988-1990 | Case-control | Population | 6478 | 0 | - |
Parazzini_1994 | Italy | 1979-1991 | Case-control | Hospital | 203 | 0 | - |
Makhseed_1994 | Kuwait | 1992-1992 | Cohort | Hospital | 8721 | 0 | - |
Khouri_1994 | Saudi Arabia | 1985-1989 | Cohort | Hospital | 25551 | 0 | - |
Taylor_1994 | USA | 1984-1987 | Case-control | Population | 1967 | 0 | AP; abortion; tobacco use |
To_1995 | Hong Kong | 1984-1993 | Cohort | Hospital | 50485 | 0 | - |
Monica_1995 | Sweden | 1983-1990 | Case-control | Population | 4676 | 0 | AP; previous previa |
Hemminki_1996 | Finland | 1987-1993 | Cohort | Population | 10889 | 1 | AP; provider |
Chelmow_1996 | USA | 1992-1994 | Case-control | Hospital | 128 | 0 | - |
Takayama_1997 | Japan | 1974-1994 | Case-control | Hospital | 264 | 0 | - |
Macones_1997 | USA | 1992-1996 | Case-control | Hospital | 120 | 0 | age; abortion; drug and tobacco use |
Ziadeh_1999 | Jordan | 1995-1996 | Cohort | Hospital | 18651 | 0 | - |
Hendricks_1999 | Singapore | 1993-1997 | Cohort | Hospital | 16169 | 0 | - |
Rageth_1999 | Switzerland | 1983-1996 | Cohort | Population | 255453 | 0 | - |
Archibong_2001 | Saudi Arabia | 1997-2002 | Cohort | Hospital | 15191 | 0 | - |
Lydon-Rochelle_2001 | USA | 1987-1996 | Cohort | Population | 95630 | 1 | AP |
Eniola_2002 | Nigeria | Case-control | Hospital | 272 | 0 | AP; abortion; SE | |
Gilliam_2002 | USA | 1986-1989 | Case-control | Hospital | 1171 | 1 | AP; abortion; tobacco use |
Tuzovic_2003 | Croatia | 1992-2001 | Case-control | Hospital | 1206 | 0 | - |
Hossain_2004 | Bangladesh | 2000-2002 | Cohort | Hospital | 2536 | 0 | - |
Olive_2005 | Australia | 1998-2002 | Cohort | Hospital | 375653 | 0 | - |
Getahun_2006 | USA | 1989-1997 | Cohort | Population | 156475 | 1 | AP; abortion; alcohol and tobacco use; prenatal care; inter pregnancy interval; SE |
Kennare_2007 | Australia | 1998-2003 | Cohort | Population | 36038 | 1 | AP; abortion |
Hung_2007 | Taiwan | 1990-2003 | Cohort | Hospital | 37702 | 0 | - |
Daltveit_2008 | Norway | 1967-2003 | Cohort | Population | 637497 | 1 | AP; delivery date |
Rahim_2009 | Pakistan | 2001-2005 | Cohort | Hospital | 20110 | 0 | - |
Yang_2009 | USA | 1995-2000 | Cohort | Population | 11026768 | 0 | AP; abortion; alcohol, tobacco and drug use; prenatal care; SE |
Rosenberg_2010 | Israel | 1988-2009 | Cohort | Hospital | 185476 | 0 | AP; abortion; fertility treatment; tobacco use |
Not including current study | Including current study | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Number of Studies | Random Effects Pooled OR | Lower 95% CI | Upper 95% CI | I2
| Number of Studies | Random Effects Pooled OR | Lower 95% CI | Upper 95% CI | I2
| ||
Overall
|
37
|
2.199
|
1.964
|
2.462
|
86.1%
|
38
|
2.155
|
1.941
|
2.395
|
86.0%
| |
Study design
| |||||||||||
Cohort studies | 23 | 2.345 | 2.045 | 2.690 | 89.7% |
24
|
2.284
|
2.014
|
2.591
|
89.5%
| |
Case-control studies | 14 | 1.933 | 1.517 | 2.464 | 71.0% | 14 | 1.933 | 1.517 | 2.464 | 71.0% | |
Setting
| |||||||||||
Population-based studies | 11 | 1.674 | 1.549 | 1.809 | 86.7% |
12
|
1.664
|
1.553
|
1.785
|
56.0%
| |
Hospital-based studies | 26 | 2.677 | 2.146 | 3.339 | 86.8% | 26 | 2.677 | 2.146 | 3.339 | 86.8% | |
Timing of PP diagnosis
| |||||||||||
Confirmed at CS | 13 | 2.515 | 1.751 | 3.613 | 88.2% | 13 | 2.515 | 1.751 | 3.613 | 88.2% | |
Other | 24 | 1.982 | 1.781 | 2.206 | 80.9% |
25
|
1.936
|
1.756
|
2.135
|
80.7%
| |
Inclusion criteria
| |||||||||||
Studies analyzing 2nd births only | 7 | 1.504 | 1.383 | 1.635 | 0% |
8
|
1.540
|
1.442
|
1.645
|
0%
| |
Other | 30 | 2.462 | 2.138 | 2.835 | 87.6% | 30 | 2.462 | 2.138 | 2.835 | 87.6% | |
Risk-adjustment
| |||||||||||
Adjusted for age and parity | 14 | 1.648 | 1.515 | 1.792 | 52.3% |
15
|
1.642
|
1.524
|
1.769
|
54.1%
| |
Unadjusted estimates | 23 | 2.712 | 2.174 | 3.383 | 87.7% | 23 | 2.712 | 2.174 | 3.383 | 87.7% |