Outcomes of pregnancies following a birth with major birth defects: a population based study

Parents whose first infant had birth defects may worry about a new pregnancy. Our aim was to study pregnancy outcomes among non-malformed second siblings in families where the first birth had a major birth defect.

Data were from the Medical Birth Registry of Norway from 1967 to 2004. Births were linked to their mothers through the unique national identification numbers, providing sibship files with the mother as the observation unit. The study was based on 538,669 singleton first and second full siblings. Families were classified as affected families if the first infant had a major birth defect. Pregnancy outcomes for non-malformed second siblings following affected first births were compared with second siblings in families without malformed infants. Subgroup analyses were done for families where first infants had neural tube defects, cleft lip with or without cleft palate, abdominal wall defects, limb reduction defects, pes equinovarus and congenital dysplasia of the hip.

Second siblings in affected families did not differ from those in unaffected families in risk of perinatal death, small for gestational age, preterm birth, placental abruption or preeclampsia. Second siblings following an infant with limb reduction defects had a higher risk of breech presentation than second siblings in unaffected families, also when stratifying on previous siblings in vertex presentation (stratified OR 2.20 [95% C.I. 1.17-4.15]).

Parents who proceed to a new pregnancy after a first birth with birth defects may be reassured that, given no recurring defects, there is in general no increased risk of adverse pregnancy outcomes.