This is the second piece in a two-part series about some of the reasons why some mothers opt for formula instead of breastfeeding. We have attempted to cover as many of the deciding factors across these two articles, but this is at heart a very personal, individual decision for every new mother. The first part of the series is linked at the bottom of this article.

Most mothers want to try breastfeeding. But the majority don't stick with it through the first six months of a child's life. That can be due to structural issues like a lack of help at the hospital, aggressive marketing by companies that make baby formula or a need to go back to work.

But sometimes the reasons aren't only structural. In some cases, women with ample maternity leave experience enormous pressure to breastfeed. But not everyone can do it.

Family pressure

Lala Prada Streithorst is a mother of a 5-year-old boy and lives in Berlin. When Streithorst gave birth to her son in her home country of Colombia, she was heavily pressured by family members to breastfeed. But she became pregnant shortly after a gastric bypass surgery and that made it hard for her to drink a lot of liquid, which, in turn, affected her ability to produce enough milk for her baby.

Breastfeeding did not come easy to Streithorst ― and she felt guilty and anxious about it, as though she were a deficient mother because she couldn't feed her child with her own breast milk.

She decided to start feeding the baby 80% formula and 20% breast milk. But even that 20% hurt. By the fifth month, she decided the pain and stress wasn't worth it and started exclusively feeding her baby formula. Today, her son is a healthy 5-year-old.

Pressure from all sides

There are other reasons why some women cannot produce enough milk for their babies.

Dominique Hiller, who works in tech in Berlin, started breastfeeding her first baby but had trouble the entire time. It was very difficult for her to produce enough milk, but her doctors and midwife told her to keep at it.

But they didn't ask about her health history, although that ended up explaining what was going on with her milk supply — Hiller has problems with her thyroid, which studies suggest is one of the prime reasons why some women cannot produce enough milk.

"It was painful. I was not producing much milk. The kid was crying. My partner was like, 'why is the kid crying' — I also had that kind of pressure. And the midwife said, 'Yeah, but you need to breastfeed.' And so it was really a tension between a crying kid, partner and the midwife," she said.

Some women experience pressure when they opt for the bottle instead of the breast.

Emanuela Damiani, who also works in tech in Berlin, knew she wanted to breastfeed from early on. But she also wanted to work, so she decided she would sometimes pump and use the bottle.

She hadn't planned to introduce the bottle until the third month, but early on she realized, during a routine checkup, that the baby wasn't gaining weight.

At first, Damiani worried she wasn't producing enough milk, but her doctor said the baby just wasn't latching properly to her breast, which is what babies need to do to get to the milk. 

After lots of trying without much luck, Damiani decided to introduce the bottle sooner than planned. When she told her midwife what she wanted to do, the midwife was supportive, but asked Damiani not to tell anyone that she had given it the OK.

"The midwife said 'I'm glad that you're OK with this, because I also think it's the easiest solution. Just don't tell anyone that I support this, because there is a bit of a breastfeeding mafia. People can be really judgmental about it,'" said Damiani.

What research says about breastfeeding and formula

Opting against breastfeeding can harm the health of infants in situations like the one in Nairobi described by Antonina Mutoro, a maternal and child well-being researcher for the African Population and Health Research Center, in the first part of this series.

It's unsafe for babies to eat solid food or cow's milk before they are six months old. Formula should always be combined with clean water and should not be diluted to last longer. This can lead to infant malnourishment.

According to the World Health Organization, 13% of global infant deaths could be prevented by exclusive breastfeeding.

But in countries where women have constant access to clean water and the money to purchase a regular supply of baby formula, research shows that whether or not a woman opts to exclusively breastfeed does not seem to make a big difference in the baby's long-term health.

In the largest randomized trial measuring the impact of breastfeeding interventions to date, the results suggested there was almost no long-term difference in the health of babies who were exclusively breastfed and those who were fed with baby formula or a mix of the two.

The authors tested the "baby friendly" approach, which promotes breastfeeding at birth and is explained in the first half of this series, in Belarus hospitals shortly after the collapse of the Soviet Union. 

They implemented the approach in a random group of new mothers and tracked others who didn't receive any sort of intervention as the control group.

In the first six months after a child's birth, the authors noticed some real differences between the two groups — the babies in the control group had more gastrointestinal tract infections and atopic eczema in the first year of life.

Better health with breastfeeding?

After six-and-a-half years, the researchers returned to the kids and ran checkups. They found that children who had been breastfed had slighter better verbal performance and IQ scores compared to those in the control group, but they observed no other differences.

At another follow-up, when the kids were 16 years old, the researchers reported just one difference between the two groups: The adolescents who had been exclusively breastfed for longer appeared to have slightly higher verbal function.

Lead study author Michael Kramer said he was disappointed by some of the results, such as that the impact on IQ seemed to diminish over time. But as a pediatrician Kramer said he still believed breastfeeding was probably the best option, if women can do it.

However, he added that it's not the most important decision a mother can make.

"How much time do you let your child spend in front of a television or in front of a computer? What kind of diet do you feed them, how much physical activity does the family get, does anybody smoke at home? Is the child wearing a helmet when they ride a bicycle or goes skiing? Attaching seat belts, child seats — all of these things are probably at least as important as whether you breastfeed," Kramer said.

Health effects are difficult to measure

No large randomized trials have measured the physical difference between breastfeeding and formula feeding on a baby's health in industrialized countries.

That's because studies instructing one group of women to use baby formula and another to breastfeed are considered unethical.

The WHO quotes observational studies that show children who are breastfed have higher IQ scores, but the studies use participants who have already opted for one of the two options.

The decision whether or not to breastfeed is heavily influenced by socioeconomic factors — women who exclusively breastfeed are statistically more educated and wealthier. This makes it largely impossible to singularly measure the impact breast milk might have on outcomes like IQ.

If you want to read more on the issue of breastfeeding and baby formula, you can find part one in this series here.

Edited by: Zulfikar Abbany, Carla Bleiker