Risk indicators of reduction limb defects.

The birth of a child with a reduction limb defect (RLD) was evaluated in relation to vaginal bleeding, threatened abortion, and other complications of pregnancy, placental weight, birth weight, family history, parental age, and the outcome of previous pregnancies. The material consisted of 453 cases of reduction limb defect and an equal number of non-malformed controls matched for time and place. The children were born in Finland during 1964-77. The cases with reduction limb defect without additional malformations were analysed separately. Statistically significant associations were found between the occurrence of reduction limb defect and the following risk indicators: vaginal bleeding, threatened abortion, duration of gestation under 37 weeks, placental weight 400 g or less, birth weight 2500 g or less, and any type of malformation in the relatives. Vaginal bleeding indicated the risk of reduction limb defect to be increased about fourfold; short gestation indicated about twofold risk of reduction limb defect as an isolated malformation. Both low placental weight and low birth weight were associated to a threefold risk of an isolated reduction limb defect. These factors of an abnormal pregnancy indicated even higher risk of reduction limb defect with additional malformations. Preliminary genetic analysis suggests that hereditary factors play no major part in the aetiology of reduction limb defects.