Routine ultrasound examination at 41 weeks of gestation and risk of post-term severe adverse fetal outcome: a retrospective evaluation of two units, within the same hospital, with different guidelines

Authors

  • PG Lindqvist,

    Corresponding author
    1. Department of Obstetrics and Gynaecology, Clintec, Karolinska Institute, Karolinska University Hospital, Huddinge, Stockholm, Sweden
    • Correspondence: PG Lindqvist, Department of Obstetrics and Gynaecology, Clintec, Karolinska University Hospital, Huddinge, Kvinnokliniken K 57, SE-14186 Stockholm, Sweden. Email Pelle.lindqvist@ki.se

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  • K Pettersson,

    1. Department of Obstetrics and Gynaecology, Clintec, Karolinska Institute, Karolinska University Hospital, Huddinge, Stockholm, Sweden
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  • A Morén,

    1. Department of Obstetrics and Gynaecology, Clintec, Karolinska Institute, Karolinska University Hospital, Huddinge, Stockholm, Sweden
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  • M Kublickas,

    1. Department of Obstetrics and Gynaecology, Clintec, Karolinska Institute, Karolinska University Hospital, Huddinge, Stockholm, Sweden
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  • L Nordström

    1. Department of Mothers and Childrens Health, Karolinska University Hospital, Solna, Stockholm, Sweden
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Abstract

Objective

To study whether a routine with a routine ultrasound examination (routine scan) at 41 gestational weeks as compared with ultrasound on clinical indication (indicated scan), lowered the risk of severe adverse fetal outcome in post-term period.

Design

A retrospective cohort study.

Setting

Karolinska University Hospital, Stockholm, Sweden.

Population

Eight years of deliveries, 2002–2009.

Method

One of the two delivery units at Karolinska University Hospital used a routine scan at 41 week of gestation and the other unit used an indicated scan. Severe adverse fetal outcome were defined: severe asphyxia, death or cerebral damage. The study was analysed using logistic regression with adjustment for potential confounders.

Main outcome measures

Differences in post-term severe adverse fetal outcome.

Results

No increased risk of post-term severe adverse fetal outcome was seen at the unit using a routine scan; conversely, a 48% significantly increased risk was seen at the unit using an indicated scan (OR 0.89, 95% confidence interval, CI, 0.5–1.5 and OR 1.48, 95% CI 1.06–2.1, respectively). Comparing post-term periods, there was no significantly increased risk at the unit using indicated scans (OR 1.6, 95% CI 0.9–3.0). There was a 60% increased prevalence of small-for-gestational age (SGA) newborns in the post-term period at the unit using indicated scans (OR 1.6, 95% CI 1.1–2.4), but no differences in operative delivery.

Conclusion

A policy to use routine scans at 41 weeks of gestation seems to normalise an increased post-term risk of severe adverse fetal outcome, possible due to increased awareness of SGA and/or oligohydramniosis.

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