Nearly 1 in 3 women who give birth in the United States have a caesarean section and around 50 percent have their labor induced or augmented—sped up with synthetic hormones.

Our new research, published in the journal Birth, found that babies born via medical or surgical intervention were at increased risk of health problems. These include short-term concerns such as jaundice and feeding problems, and longer-term illnesses such as diabetes, respiratory infections, and eczema.

Intervention will sometimes be required in childbirth, but should only occur when medically necessary.

What Did We Find?

Our international team, based in five countries, analyzed data from nearly 500,000 healthy, low-risk women who gave birth in New South Wales, Australia, between 2000 and 2013, and their children. We looked at their children’s health in the first 28 days and up to 5 years of age.

We found the following:

• Babies who experienced an instrumental birth (forceps or vacuum) following induction or augmentation had the highest risk of jaundice and feeding problems requiring treatment in the first 28 days.
• Babies born by caesarean section had higher rates of being cold and needing treatment in the hospital for this compared to babies born via vaginal birth.
• Children born by emergency caesarean section had the highest rates of metabolic disorders (such as diabetes and obesity) by 5 years of age.
• Rates of respiratory infections, such as pneumonia and bronchitis, metabolic disorders, and eczema were higher among children who experienced any form of birth intervention than those born vaginally.

Our study adds to the growing scientific evidence that children born by spontaneous vaginal birth have fewer short- and long-term health problems.

The findings hold even when you take into account the reason that might pre-empt the intervention, such as a mother with diabetes or high blood pressure. We removed all women with such risk factors from the study.

Why the Increased Risk?

This study showed an association between common forms of medical and surgical intervention and certain health outcomes for the child. It didn’t find one thing caused the other. But there are some obvious reasons for some of the links.

Reasons for the increased risk of longer-term problems are much less clear, but there are a couple of interesting hypotheses.

The first key theory is based on epigenetics: that life events affect how genes function and are passed on to the next generation.

Labor and birth exert a positive form of stress on the fetus, which impacts on the genes responsible for fighting off bugs, regulating weight, and suppressing tumors. Too little stress (no labor and elective caesarean section) or too much stress (induced or augmented labor and instrumental birth) could impact the expression of these genes.

The second key theory is the extended hygiene hypothesis. This suggests that vaginal birth provides an important opportunity to pass gut bacteria from mother to baby to produce a healthy microbiome and protect us from illness.

If we have an unhealthy microbiome, we may be more vulnerable to infections, allergies, diabetes, and obesity.

How to Reduce Unnecessary Birth Intervention

Recently released guidelines from the World Health Organization (WHO) recommend ways to reduce unnecessary intervention by encouraging evidence-based clinical care:

1. Ensure continuity of care, in which women see the same health practitioner throughout pregnancy, during the birth, and in the postnatal period. This reduces the risk of unnecessary interventions.
2. Don’t intervene too early. Women progress much more slowly in labor than we previously thought. For 70 years, clinicians believed the cervix should dilate by 1 centimeter (0.39 inch) per hour. If the cervix was slower to dilate, intervention was initiated because labor was thought to have slowed. We now know labor progresses more slowly.
3. Don’t use continuous electronic monitoring to monitor the baby, unless there are significant risk factors. Instead, listen in regularly with a small, hand-held monitor. Continuous monitoring increases intervention rates for low-risk women and healthy babies without improving outcomes for babies.

Introducing a more evidence-based approach to care during labor and birth can increase the rates of spontaneous vaginal birth and reduce unnecessary intervention.

When Intervention Is Necessary

A certain level of intervention during childbirth improves outcomes for women and babies. But WHO recommends that the caesarean rate should be under 15 percent.

If you need to have your labor induced or augmented, or require an instrumental birth or a caesarean section due to complications, there are some things to help modify the long-term effects on your child. Seek uninterrupted skin-to-skin contact after the birth and exclusively breastfeed, if you can.

It is important for women and their partners to have all the information about both short- and long-term effects of intervention to make truly informed decisions about care during pregnancy and birth.

Hannah Dahlen is a professor of midwifery at the Western Sydney University in Australia, and Lilian Peters is a postdoctoral research fellow at Vrije Universiteit in Amsterdam. This article was originally published on The Conversation.