You are probably sleeping more hours than you think, and it is not helping
Measured with a wrist monitor from two weeks to four months, new mothers slept 7.2 hours a night, and that figure did not move. The hours were never the problem.
Almost everything you have been told about sleep after a birth comes from people repeating each other. One study put wrist monitors on about 70 American women and recorded every night from week 2 to week 16 after birth. Not a questionnaire. A machine, worn continuously, at West Virginia University.
Here is what it found.
| Measured across weeks 2 to 16 | Value |
|---|---|
| Sleep at night | 7.2 hours (standard deviation 0.95), and it did not change significantly across the four months |
| Sleep efficiency, week 2 | 79.7% |
| Sleep efficiency, week 16 | 90.2% |
| Fragmentation index, week 2 | 21.7 |
| Fragmentation index, week 16 | 12.8 |
Seven hours. That is not what anyone expects, including the people who ran the study. They said so in print:
We expected to find that postpartum mothers' total sleep time would be low, that their sleep would be highly fragmented, and that these effects would remain constant across the first several postpartum months. Instead we found that on average postpartum mothers slept over seven hours at night, and this was the only measure that remained constant across the first four postpartum months.
So why does it feel the way it feels? Because of the second column. Sleep efficiency is the share of the time you spend in bed that you are actually asleep. At two weeks these women were asleep for four fifths of their time in bed. The authors put the missing part in one sentence:
Although postpartum women obtained more total sleep time than we expected, it is important to consider this value in the context that their sleep was highly fragmented (mothers were awake nearly 2 hours during the night) throughout the early postpartum months, resulting in low sleep efficiency and necessitating a prolonged period dedicated to sleep in order to obtain this amount.
Read the numbers again with that in mind. Total sleep stayed flat while efficiency climbed from 79.7% to 90.2%. That can only happen one way: these women were not getting more sleep as the months passed, they were spending less time in bed to get the same amount. What improved was the interruption, not the total.
The authors compared the pattern they saw to sleep apnea and periodic limb movement disorder rather than to sleep deprivation. Total hours preserved, sleep broken into pieces, daytime function poor. If you feel wrecked on seven hours, that is the recognised shape of a fragmented night, not a failure of attitude.
"Can we talk about how broken my sleep is, rather than how long it is?"