Does pregnancy increase the risk of multiple sclerosis?

The association of pregnancy and onset or relapse of multiple sclerosis is well known to every clinician and raises practical problems in clinical work. The problem of the relationship between multiple sclerosis and pregnancy and childbirth had been the subject of several investigations. Early investigators (Beck, 1913) considered pregnancy so detrimental to patients with multiple sclerosis that therapeutic abortion was recommended. However, termination of pregnancy did not guarantee remission (von Hoesslin, 1934). Millar, Allison, Cheeseman, and Merrett (1959), in a careful analysis of the subject, concluded that the exacerbation rate of multiple sclerosis among women who had been pregnant was increased as compared with women who had not been pregnant, and Schapira, Poskanzer, Newell, and Miller (1966) also found that the frequency of relapse among women with multiple sclerosis who had been pregnant was somewhat higher than in non-pregnant patients. In contrast to the above studies, there are others which purport to have found no detrimental effect of pregnancy upon the course of the disease (Muller, 1949; Tillman, 1950; McAlpine and Compston, 1952). Kurland (1952) pointed out that the childbearing period corresponds to the ages during which multiple sclerosis is active, namely, 15 to 45. If a woman were pregnant only three times then she would spend about 36 months in a pregnant or post-partum state and chance association with the onset or exacerbation of multiple sclerosis of about the extent reported would be possible. If pregnancy and delivery had an aetiological role in the pathogenesis of multiple sclerosis, then a comparison of the obstetrical histories of patients with multiple sclerosis and controls before the onset of illness might be of interest. The present study uses this approach, comparing the obstetrical history of