Testing in pregnancy when there is poor growth of the baby

A baby may not grow at the predicted rate during pregnancy and be born with a low birthweight. This can result in problems for both mother and baby. When poor growth of the baby is suspected during pregnancy, antenatal care includes a combination of tests that are carried out at regular intervals to assess the health of the developing baby. Based on knowledge of the progressive changes any deterioration in the baby’s condition can be detected, which allows optimal timing of the birth so that the baby is in the best condition possible. The specified frequency and combinations of tests varies with local and personal policies. Tests may include fetal movement monitoring, fetal heart rate, growth scans, Doppler ultrasound to measure blood flow, and changes in fetal heart rate with movement to check for possible stillbirth.

The review authors identified only one controlled trial, from New Zealand. This trial randomised 167 women who were between 24 and 36 weeks' pregnant where ultrasound showed a small-for-gestational-age baby. They received a set combination of tests either twice-weekly or fortnightly. With more frequent testing, women were 25% more likely to have induced labour. Overall their babies were born four days earlier than in the fortnightly surveillance group where spontaneous onset of labour was more likely to occur. The mean gestational age at birth was just under 38 weeks in the twice-weekly group and just over 38 weeks in the fortnightly group, which was unlikely to have an impact on the health of the newborn. The number of caesarean sections, either for fetal distress or because of failure of induction, was no different. No information was available on length of antenatal hospital admission or operative vaginal births and infants were not followed up to determine neurodevelopment and cerebral palsy. This study excluded pregnancies with abnormal Doppler studies and disorders of the amniotic fluid. More studies are needed and the women’s views on the testing are also important.

Authors' conclusions: 

There is limited evidence from randomised controlled trials to inform best practice for fetal surveillance regimens when caring for women with pregnancies affected by impaired fetal growth. More studies are needed to evaluate the effects of currently used fetal surveillance regimens in impaired fetal growth.

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Background: 

Policies and protocols for fetal surveillance in the pregnancy where impaired fetal growth is suspected vary widely, with numerous combinations of different surveillance methods.

Objectives: 

To assess the effects of antenatal fetal surveillance regimens on important perinatal and maternal outcomes.

Search strategy: 

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (29 February 2012).

Selection criteria: 

Randomised and quasi-randomised trials comparing the effects of described antenatal fetal surveillance regimens.

Data collection and analysis: 

Review authors R Grivell and L Wong independently assessed trial eligibility and quality and extracted data.

Main results: 

We included one trial of 167 women and their babies. This trial was a pilot study recruiting alongside another study, therefore, a separate sample size was not calculated. The trial compared a twice-weekly surveillance regimen (biophysical profile, nonstress tests, umbilical artery and middle cerebral artery Doppler and uterine artery Doppler) with the same regimen applied fortnightly (both groups had growth assessed fortnightly). There were insufficient data to assess this review's primary infant outcome of composite perinatal mortality and serious morbidity (although there were no perinatal deaths) and no difference was seen in the primary maternal outcome of emergency caesarean section for fetal distress (risk ratio (RR) 0.96; 95% confidence interval (CI) 0.35 to 2.63). In keeping with the more frequent monitoring, mean gestational age at birth was four days less for the twice-weekly surveillance group compared with the fortnightly surveillance group (mean difference (MD) -4.00; 95% CI -7.79 to -0.21). Women in the twice-weekly surveillance group were 25% more likely to have induction of labour than those in the fortnightly surveillance group (RR 1.25; 95% CI 1.04 to 1.50).

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