When to deliver “idiopathic” SGA infants between 37 to 42 weeks of gestation? The impact of the week of gestation on adverse perinatal outcome

Introduction Small for gestation age (SGA) is a recognized risk factor associated with higher perinatal, neonatal and even adult complications. In SGA infants at term not fulfilling classical criteria or stigmata for placental triggered growth disordertiming of delivery remains still a matter of debate.

The aim of our study was to evaluate the outcome of SGA infants at term according to the week at delivery in otherwise uncomplicated pregnancies.

Material and methods We analyzed anonymized data of women in Switzerland from 2005-2017. Inclusion criteria were singleton pregnancy in cephalic presentation, birthweight < 10^th and >5^th percentile, and gestational age at delivery between 37 0/7 and 42 0/7 weeks of gestation. We excluded every complicated pregnancy.

Results A total of 1796 cases fullfied our criteria. Of those, 1352 (75 %) were delivered vaginally, and 473 (25 %) by cesarean section (CS) (14 % by secondary CS, and 11 % by elective CS). As expected, the rate of secondary CS (r = 0.828;p = 0.03) and vaginal deliveries (r = 0.965;p = 0.01) increased with advancing gestation. Induction of labour occurred in 308 (16.8 %) patients and increased in particular between the 40 and 41 weeks of gestation (r = 0.967;p = 0.002). Of them, 77.9 % delivered vaginally and 22.1 % with a secondary CS. The percentage of adverse outcome was 16.9 %,11.3 %,8.6 %,18.8 %, and 21.7 % for gestational week 37,38,39,41 and 42, respectively. Importantly, only three cases of intrauterine death occurred (one < 39 0/7 and two > 40 0/7 week of gestation).

Conclusion “Idiopatic” SGA infants are best delivered between 39 0/7 and 40 0/7 weeks of gestation.

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Publication History

Article published online:
07 October 2020