Are better tests needed for potential growth restriction?

This week's blog post is a continuation of last week's blog post. I'm going to tell you more about the examinations we offer to pregnant women, and in this post, it's about tests for intrauterine growth restriction.

What is offered, and why?

Growth restriction

One of my doctoral students has just completed an extensive study on trying to identify fetuses that are not growing as they should intrauterine.

What we commonly refer to as growth restrictions (IUGR, intrauterine growth restriction).

The question in the project has been whether we benefit from identifying these fetuses early, or if it makes no difference to know that the fetus is small before it is born.

Intrauterine growth restriction (IUGR)

IUGR is a pregnancy complication that occurs in about 3-5% of all pregnancies in Sweden.

This amounts to approximately 6,000 newborns per year.

Growth-restricted fetuses are at high risk of illness and death.

Intrauterine growth restriction is defined as

"a condition during pregnancy where the fetus cannot achieve its specific genetic growth potential."

A fetus can also be small for gestational age (SGA) but grow at a normal rate. SGA fetuses are small but normal.

So, there is a big difference between SGA and IUGR fetuses. But can we distinguish between them?

Symphysis-fundus measurement (SF measurement)

The method used in Sweden to detect growth restriction is repeated measurements of the symphysis-fundus measurement (SF measurement) on pregnant women.

It simply means that the midwife measures the woman's belly (=uterus) with a measuring tape.

As one can understand, this method is imprecise and subjective. It simply varies depending on who is measuring.

Ultrasound

Ultrasound weight estimation is currently done only when indicated. This means when there is a plateau or decline in SF measurement or when complications arise.

Only high-risk pregnancies undergo repeated growth checks throughout the pregnancy from the beginning.

The extent to which we detect growth restrictions with this strategy has been sparingly studied and likely varies in different parts of the country, depending on the level of education and access to healthcare in the area.

There are likely advantages to detecting growth-restricted fetuses, but the effect is debated.

A previous Swedish study on SGA

A Swedish study was conducted quite a few years ago in Malmö.

It showed a fourfold decrease in negative perinatal outcomes in SGA children when comparing the fetuses that were identified before birth with those that were not.

The percentage of SGA identified before birth in the study was 54%.

The study was done almost 20 years ago (children born between 1990-1998) during a period when routine ultrasound was performed at 32 weeks in Malmö.

No similar study has been conducted in Sweden since then, and the national guidelines for the management of SGA/IUGR have partially changed since the Malmö study was conducted.

In Malmö, for example, all Doppler examinations are performed by a few specially trained biomedical analysts, and ultrasound examinations are more centralized than in Stockholm.

Early or late growth restriction

Intrauterine growth restriction is also divided into early- and late-onset based on whether the diagnosis is made before or after 32 weeks of pregnancy.

Early and late growth restriction is now considered two different conditions with partly different causes and placental histological findings.

Causes of growth restriction

Why do some children not grow intrauterine?

The causes of growth restriction are many and can be divided into maternal, placental, fetal, and environmental factors.

Early-onset growth restriction is strongly associated with maternal medical conditions that can affect placental function, such as:

• Preeclampsia

• Chronic hypertension

• Diabetes mellitus

• Autoimmune conditions

• Thrombophilia, and therefore easier to predict.

The etiology of late-onset growth restriction is likely more multifaceted, partly unknown, and thus harder to predict.

What did our study show?

We studied deliveries in Stockholm in 2014 and 2017. Data from various Swedish registers were linked to pregnancy outcomes.

Negative outcomes for non-identified and identified growth-restricted fetuses were compared.

The primary outcome was: stillbirth, low Apgar score at 5 minutes, pH <7, or resuscitation activities >10 minutes.

Poor childhood outcomes were defined as cognitive or motor impairment such as cerebral palsy, hearing impairment, visual impairment, or death at 1-3 years of age.

Results: In the analyses, non-identified IUGR fetuses had a seven-fold increased risk of stillbirth and a 1.7-fold increased risk of poor outcomes at birth.

No association was found between prenatal identification of small-for-gestational-age and severe neonatal or poor childhood outcomes.

Conclusion: Non-identified IUGR fetuses have an increased risk of severe delivery outcomes, especially stillbirth and poorer outcomes at birth.

Despite this result, we still only perform ultrasounds on a so-called "indication."

It means that we only examine the pregnancy if we suspect that something is wrong (declining SF measurement) or if the mother/fetus is confirmed to be ill.

The question is whether we wouldn't improve our care if everyone was offered an ultrasound examination at the end of pregnancy.

Can we afford this?

You know that the economy is strained.

The question is whether we can afford not to?

/Doctor Eva