Perspectives on Sexual and Reproductive Health
Volume 34, Number 2, March/April 2002

 

Risk of Postpartum Induced Abortion in Finland:
A Register-Based Study
TABLES

TABLE 1. Number of postpartum abortions and births, by time elapsed from index birth to following conception
Months elapsed Induced abortions Births
<6 2,777 12,430
6-8 2,422 20,481
9-12 2,786 36,049
13-18 3,597 49,881
19-24 2,733 36,806
Note: Based on conceptions within two years of the 567,128 index births that occurred in the period 1987-1995.

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TABLE 2. Relative risks of induced abortion (and 95% confidence intervals), as estimated from a hazard regression model, and odds ratios showing relative abortion ratios (and 95% confidence intervals), as estimated from a logistic regression model, all by selected characteristics
Characteristic Relative abortion risk Relative abortion ratio
Time since birth (mos.)
3-5 0.97 (0.92-1.03) 2.08 (1.96-2.21)*
6-8 1.14 (1.08-1.20)* 1.41 (1.33-1.49)*
9-12 1.08 (1.02-1.13)* 0.99 (0.94-1.05)
13-18 1.10 (1.05-1.15)* 0.99 (0.94-1.04)
19-24 (ref) 1.00 1.00
25-30 1.05 (1.00-1.11) 1.13 (1.06-1.19)*
31-36 0.97 (0.91-1.03) 1.25 (1.17-1.33)*
37-42 0.97 (0.91-1.03) 1.38 (1.29-1.48)*
43-48 0.99 (0.93-1.06) 1.58 (1.47-1.70)*
49-54 1.00 (0.94-1.08) 1.79 (1.66-1.94)*
55-60 0.94 (0.87-1.02) 1.86 (1.71-2.03)*
Current age
14-19 1.95 (1.82-2.08)* 2.11 (1.95-2.28)*
20-24 (ref) 1.00 1.00
25-29 0.49 (0.47-0.50)* 0.56 (0.54-0.59)*
30-34 0.32 (0.31-0.33)* 0.51 (0.49-0.53)*
35-39 0.25 (0.24-0.26)* 0.62 (0.59-0.66)*
40-44 0.21 (0.19-0.23)* 1.21 (1.11-1.33)*
Marital status at birth
Married (ref) 1.00 1.00
Cohabiting 2.16 (2.10-2.23)* 2.55 (2.47-2.63)*
Never-married 2.99 (2.87-3.11)* 4.68 (4.48-4.89)*
Widowed 2.27 (1.58-3.25)* 2.23 (1.45-3.42)*
Divorced 3.76 (3.47-4.07)* 3.75 (3.41-4.14)*
Parity
1 (ref) 1.00 1.00
2 1.49 (1.45-1.54)* 3.49 (3.38-3.61)*
3 2.17 (2.08-2.26)* 5.64 (5.41-5.89)*
>=4 2.32 (2.20-2.45)* 2.80 (2.63-2.97)*
Intercept .001391 .03982
*p<.05. Notes: For each measure, results of a likelihood ratio test indicated that each variable was significant at p<.001. ref=reference group.

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FIGURE 1. Monthly number of postpartum conceptions per 1,000 person-years, by time elapsed since index birth

Notes: Conceptions include pregnancies that ended in live birth, induced abortion or miscarriage. Age-standardized relative risks were estimated from a hazard regression model including time elapsed since index birth and age. They were converted to the absolute risk per 1,000 person-years using as the reference point the unstandardized rate at 19-24 months from the index birth.

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FIGURE 2. Monthly number of postpartum abortions per 1,000 person-years, by time elapsed since index birth

Notes: Conceptions include pregnancies that ended in live birth, induced abortion or miscarriage. Age-standardized relative risks were estimated from a hazard regression model including time elapsed since index birth and age. They were converted to the absolute risk per 1,000 person-years using as the reference point the unstandardized rate at 19-24 months from the index birth.

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FIGURE 3. Relative risk of postpartum abortion, by time elapsed since index birth, according to age, marital status at index birth and parity
AGE
MARITAL STATUS AT INDEX BIRTH
PARITY

Notes: Relative risks were estimated using hazard regression models that included age, parity and the interaction of the variable being examined with time elapsed since delivery. Reference categories were 20-24-year-olds, married women and women at parity one, all at 19-24 months postpartum.

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FIGURE 4. Unstandardized and age-standardized monthly abortion ratios, by time elapsed since index birth

Notes: The abortion ratio represents the ratio of conceptions leading to abortions to conceptions leading to births. The time reference for both abortions and births was the month of conception. Age-standardized relative abortion ratios (odds ratios) were estimated from a logistic regression model including time elapsed since index birth and age. They were converted to absolute ratios using as the reference point the unstandardized ratio at 19-24 months from the index birth.


FIGURE 5. Abortion risk and abortion ratio within the first eight months postpartum relative to 1987-1988 value, by year of index birth, according to age

Note: Relative risks were estimated by models including time elapsed since index birth, parity and the interaction of age and year, where the year of the index birth was grouped into two-year groups.

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© copyright 2001, the Alan Guttmacher Institute.