Prenatal termination of pregnancy may underestimate risks or cause bias in epidemiological studies of birth defects if such studies measure only defects diagnosed postnatally. We aimed to estimate the proportion of all fetuses with birth defects terminated in the second trimester of pregnancy-overall and for specific defects.
The study comprised all pregnancies ending in a singleton birth, miscarriage, or termination of pregnancy for which health care services were sought, as recorded in Danish medical registries between 1 January 2007 and 31 December 2011.
Of the 420,090 pregnancies, 307,637 fetuses survived until gestational week 12 or beyond; of these, 296,373 (96%) ended in a live birth or stillbirth and 11,264 (4%) ended in a second-trimester termination. The prevalence of birth defects among live births and stillbirths was 3% (9,790/296,373); the corresponding prevalence among second-trimester-terminated pregnancies was 14% (1,563/11,264). Although only 4% of all pregnancies ended in a second-trimester termination, 14% (1,563/11,353) of pregnancies with birth defects were ended by a second-trimester termination. The groups of birth defects with the highest proportion of second-trimester terminations were defects of the nervous system (347/740; 48%) and abdominal wall (58/149; 39%). For many types of birth defects, however, that proportion was less than 10%.
The proportion of terminated pregnancies carrying birth defects is considerably greater than the corresponding proportion for pregnancies that end as live births or stillbirths. The proportion of birth defects unobserved at birth due to second-trimester terminations depends on type of defect and lethality.
Wow. One in 25 babies who make it to the 2nd trimester dies as a result of abortion.
One in 7 pregnancies with a "birth defect" ended in termination.
It would be interesting to know the Canadian numbers for this.
But of course, since this information is only available to health researchers, and the numbers are not very good to begin with, it would only be a vague estimate.
What I thought was interesting was that there was no mention of Down Syndrome.
I'm not sure it qualifies as "defects of the nervous system."
I checked a definition of "birth defect".
It includes congenital anomalies.
So I'm a little puzzled as to whether Trisomies and similar genetic conditions are included in the calculation.
Epidemiology. 2014 Aug 27. [Epub ahead of print]
Estimating the Proportion of all Observed Birth Defects Occurring in Pregnancies Terminated by a Second-trimester Abortion.
Svensson E1, Ehrenstein V, Nørgaard M, Bakketeig LS, Rothman KJ, Toft Sørensen H, Pedersen L.