2003 Calhoun-Rooney
THE 2003 CALHOUN-ROONEY LITERATURE REVIEW: Lumley Study, 1993 and 98; Bavarian Study, 1998; Danish Study, 1999
Reference: Calhoun, B, Rooney, B; Induced Abortion and Risk of Later Premature Birth; (Journal of American Physicians and Surgeons, Volt 8, #2, 2003). Calhoun and Rooney comment on 4 important studies dating from 1993 to 1999.
The Lumley studies of 1993 and 1998
Calhoun and Rooney reported on 1993 Australian study by Lumley of 121,305 births. See Table 1 for results:
| Number of prior IAs | 1998 study | |||
| 1 | 2 | 3 | 4+ | |
| Gestational age | RR | RR | RR | RR |
| 20-27 wks(XPB) | 1.6` | 2.5 | 5.6 | 9 |
| 28-31 wks | 1.5 | 1.1 | 2.6 | |
| 32-36 wks | 1.1 | 1.6 | 2.4 | |
Table 1: Premature birth risk by # of prior induced abortions compared with outcome of first pregnancies.(Lumley, “The epidemiology of Pre term birth, Baillieres “Clinical OBGYN, 1993:7(3)477-498). Also Lumley in Prenatal Neonatal Med 1998; 3:21-24) (244,000 live births)
Most of the induced abortions reported in this study were by vacuum aspiration, which would be the least traumatic method for the cervix. Nevertheless, these IA’s resulted in the significant increases in PTB. Notice that the Extreme Preterm Birth (XPB) category is inordinately affected, with doubling of XPB with just 2 IA’s, an increase of over 5 times the expected rate with 3 IA’s, and an astounding nine-fold increase with 4 or more induced abortions (the latter figure from a 1998 study by Lumley, analyzing 243,679 live births.)
The Bavarian Study, 1998
Calhoun and Rooney reported on a1998 study from Bavaria of 106,345 births. See Table 2 for results.
Martius, et.al; “Risk factors…” EuroJ.ObGynReproBiol1998;80:183-189)
| Number of prior IAs | |||
| 1 | 2 | 3 or more | |
| Gestational age | RR | RR | RR |
| 32 weeks | 2.5 | 5.2 | 8.0 |
| <37 weeks | 1.5 | 2.1 | 3.6 |
Note again, the dose response (more IA’s produce more PTB). Note also the inordinate increase in Early Preterm Birth (under 32 weeks) associated with repeat induced abortion–an eightfold increase after 3 induced abortions
The Danish Study, 1999
Calhoun and Rooney reported on 1999 Danish study, which showed that a mid trimester abortion by D&E, (dilatation and evacuation) increased the risk of PTB substantially. This seems logical, as the D&E procedure necessarily results in more cervical trauma than a simple suction curettage. One prior D&E more than doubled the PTB rate, and two prior D&E’s increased the risk 12 times higher than the rate for women with no abortion history.(Zhou, Sorenson, Olsen, “Induced abortion and subsequent pregnancy duration,” Obstet Gynecol 1999;94:948-953)