Feeding is hard in the first week even when everything is being done right
Under close to ideal study conditions, 22% of mothers had lactation start later than 72 hours and 12% of babies lost 10% or more by day 3.
The most useful feeding study for a new parent is not the one with the biggest numbers. It is the one run under the best possible conditions, because it tells you what happens when nothing has gone wrong.
The study. Every mother in Davis, California who gave birth to a healthy single term baby at one of five hospitals during a ten-month period in 1999, and who was willing to try to breastfeed exclusively for at least a month. 280 of 328 eligible mothers took part. Lactation guidance was provided. Trained lactation consultants assessed the feeding on days 0, 3, 5, 7 and 14. This is close to the most favourable setting that has ever been studied.
| What happened, in 280 motivated and supported mother and baby pairs | How often |
|---|---|
| Feeding going poorly on day 0 | 49% |
| Feeding going poorly on day 3 | 22% |
| Feeding going poorly on day 7 | 14% |
| Milk coming in later than 72 hours | 22% of women |
| Baby losing 10% or more of birth weight by day 3 | 12% of babies |
One mother in five had her milk come in later than three days. One baby in eight had lost a tenth of its birth weight by day 3. That is what the first week looks like with a lactation consultant in the room.
The two findings are linked, and the link is worth stating with both numbers attached. Excess weight loss was 7.1 times more likely if the mother's milk came in late. The starting point that multiplier applies to is 12%, and the study reports no serious outcomes in any of these babies. A large multiplier on a common, self-correcting event is not the same as a large danger.
The authors' own recommendation was simply that All breastfeeding mother-infant pairs should be evaluated at 72 to 96 hours' postpartum.
That is the window in which most of this resolves or gets help.
Formula in the first two days is common, and the denominator is usually misquoted. Among US babies born in 2023 who were ever breastfed, 22.6% received formula before 2 days of age. That is 22.6% of breastfed babies, not of all babies; CDC's own footnote says so. Ever breastfed was 86.1%.
What a normal newborn actually does. Pooled diary studies of 8,690 infants found average fussing and crying of 117 to 133 minutes per 24 hours from one to two weeks through six weeks of age, falling to about 68 minutes by 10 to 12 weeks. Between 17% and 25% of babies met the standard research criteria for colic in the first six weeks. The same analysis found no statistical support for the universally taught six-week crying peak. A baby who cries about two hours a day is doing what most babies do, and it is usually read as a feeding failure when it is not one.
Going home is not always the end of it. In a California study of 2,824,963 births from 2011 to 2017, 5.9% of healthy late preterm babies (7,243 of 122,014) were readmitted within 30 days, at 2.34 times the odds of term babies. Nearly six in ten of those readmissions (58.9%) were for jaundice, which in the first week is as often a feeding problem as a liver problem. The term readmission rate is not reported in that study, so this guide does not give one.
"Who do I call at 2am if feeding is not working?"
"When exactly is my baby being weighed and seen again?"
"What signs would mean I should bring my baby back rather than wait for the appointment?"