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. 2021 Jun 4;11:11834. doi: 10.1038/s41598-021-91271-7

Association of maternal sleep before and during pregnancy with sleep and developmental problems in 1-year-old infants

Kazushige Nakahara 1,#, Takehiro Michikawa 2,#, Seiichi Morokuma 3,4,✉, Masanobu Ogawa 4, Kiyoko Kato 1,4, Masafumi Sanefuji 4,5, Eiji Shibata 6,7, Mayumi Tsuji 6,8, Masayuki Shimono 6,9, Toshihiro Kawamoto 6, Shouichi Ohga 5, Koichi Kusuhara 6,9; the Japan Environment and Children’s Study Group
PMCID: PMC8178306  PMID: 34088929

Abstract

This study investigated the association of maternal sleep before and during pregnancy with sleeping and developmental problems in 1-year-old infants. We used data from the Japan Environment and Children’s Study, which registered 103,062 pregnancies between 2011 and 2014. Participants were asked about their sleep habits prior to and during pregnancy. Follow-up assessments were conducted to evaluate the sleep habits and developmental progress of their children at the age of 1 year. Development during infancy was evaluated using the Ages and Stages Questionnaire (ASQ). Maternal short sleep and late bedtime before and during pregnancy increased occurrence of offspring’s sleeping disturbances. For example, infants whose mothers slept for less than 6 h prior to pregnancy tended to be awake for more than 1 h (risk ratio [RR] = 1.49, 95% confidence interval [CI] 1.34–1.66), sleep less than 8 h during the night (RR = 1.60, 95% CI 1.44–1.79), and fall asleep at 22:00 or later (RR = 1.33, 95% CI 1.26–1.40). Only subjective assessments of maternal sleep quality during pregnancy, such as very deep sleep and feeling very good when waking up, were inversely associated with abnormal ASQ scores in 1-year-old infants.

Subject terms: Medical research, Risk factors

Introduction

Sleep duration among the general population in Japan has been reported to be shorter than that in other countries1 and has become even shorter in recent years2. Furthermore, it has been reported that approximately 10% of infants have sleeping problems3. Neurodevelopmental disorders, including autism spectrum disorder (ASD), neurodevelopment abnormalities, and disturbed sleep habits, such as late bedtime and intense night crying, are observed in early infancy4. The incidence of developmental disorders is increasing in developed countries, including Japan5–7. Factors related to developmental disorders include genetic ones and environmental (in utero) ones8,9. Maternal lifestyle such as sleep pattern may affect the offspring’s sleep and development.

It has been reported that maternal sleep disorders are associated with developmental progress in the offspring. For example, maternal sleep disordered breathing (SDB) during pregnancy is associated with the offspring’s development, manifesting as disrupted social skills and low reading-test scores10,11. Thus, not only maternal sleep habit but also maternal sleep disorders during pregnancy may be related to early infant sleep patterns and development. However, no large-scale study has examined the potential associations between maternal sleep and the offspring’s sleep patterns or development. Additionally, the importance of maternal sleep during various periods of pregnancy and the persistence of the influence remain unclear.

We previously reported that maternal sleep habits, such as short sleep duration and late bedtime, both before and during pregnancy, were associated with the offspring’s sleep problems and temperament at 1 month of age12. We hypothesize that maternal sleep before and during pregnancy would continue to be associated with the infant’s sleep and developmental problems even at 1 year of age.

This study aimed to expand on those findings and investigate the association between maternal sleep habits, before and during pregnancy, with offspring outcomes at 1 year of age.

Results

The baseline characteristics of the participants, along with the available data on sleep duration before pregnancy, are shown in Table 1. The characteristics of participants in the various sleep groups are also shown in Supplemental Table 1. The reported sleep duration was on average between 7 and 8 h, both before and during pregnancy. The participants tended to sleep longer and go to bed earlier during pregnancy than before pregnancy. Significant data points are summarized below and include risk ratios (RR) and 95% confidence intervals (CI) in the multivariable model, adjusted for maternal age at delivery, smoking habits, alcohol consumption, pre-pregnancy body mass index, gestational age at birth, parity, infertility treatment, and infant sex.

Table 1.

Baseline characteristics of the study population stratified by sleep duration before pregnancy.

Maternal sleep before pregnancy (h)
< 6 h 6 < 7 7 < 8 8 < 9 9 < 10 10<
n % n % n % n % n % n %
Maternal sleep 4948 6.7 14,661 19.9 25,136 34.1 18,302 24.8 7494 10.2 3286 4.5
Maternal characteristics
Age at delivery (years)
 < 25 490 9.9 1025 7.0 1825 7.3 1539 8.4 827 11.0 786 23.9
 25–29 1258 25.4 3940 26.9 6968 27.7 5087 27.8 2154 28.7 1006 30.6
 30–34 1602 32.4 5278 36.0 9266 36.9 6806 37.2 2698 36.0 937 28.5
 ≥ 35 1598 32.3 4418 30.1 7077 28.2 4870 26.6 1815 24.2 557 17.0
Smoking habits
 Never smoked 2708 54.7 9026 61.6 15,537 61.8 10,935 59.8 4304 57.4 1606 48.9
 Ex-smokers who quit before pregnancy 1049 21.2 3193 21.8 5787 23.0 4550 24.9 1967 26.3 818 24.9
 Smokers during early pregnancy 1191 24.1 2442 16.7 3812 15.2 2817 15.4 1223 16.3 862 26.2
Alcohol consumption
 Never drank 1575 31.8 4819 32.9 8628 34.3 6552 35.8 2727 36.4 1193 36.3
 Ex-drinkers who quit before pregnancy 799 16.2 2365 16.1 4321 17.2 3546 19.4 1615 21.6 680 20.7
 Drinkers during early pregnancy 2574 52.0 7477 51.0 12187 48.5 8204 44.8 3152 42.1 1413 43.0
Pre-pregnancy body mass index (kg/m2)
 < 18.5 790 16.0 2349 16.0 4023 16.0 2949 16.1 1188 15.9 586 17.8
 18.5–24.9 3618 73.1 10,909 74.4 18,658 74.2 13,549 74.0 5534 73.9 2367 72.0
 ≥ 25.0 540 10.9 1403 9.6 2455 9.8 1804 9.9 772 10.3 333 10.1
Parity
 0 2982 60.3 8643 59.0 12,176 48.4 5950 32.5 1748 23.3 1326 40.4
 ≥ 1 1966 39.7 6018 41.1 12,960 51.6 12,352 67.5 5746 76.7 1960 59.7
Infertility treatment
 No 4573 92.4 13,482 92.0 23,252 92.5 17,197 94.0 7175 95.7 3158 96.1
 Ovulation stimulation/artificial insemination by sperm from husband 202 4.1 641 4.4 1005 4.0 640 3.5 190 2.5 72 2.2
 Assisted reproductive technology 173 3.5 538 3.7 879 3.5 465 2.5 129 1.7 56 1.7
Gestational age (weeks)
 Early term (37–38) 1565 31.6 4573 31.2 8099 32.2 6164 33.7 2581 34.4 1070 32.6
 Full term (39–41) 3383 68.4 10,088 68.8 17,037 67.8 12,138 66.3 4913 65.6 2216 67.4
Infant sex
 Boys 2508 50.7 7434 50.7 12,758 50.8 9323 50.9 3879 51.8 1686 51.3
 Girls 2440 49.3 7227 49.3 12,378 49.2 8979 49.1 3615 48.2 1600 48.7
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Maternal sleep before pregnancy and infant sleep (Table 2)

Table 2.

Association between sleep before pregnancy and infant sleep, Japan Environment and Children’s Study (2011–2014).

No. of participants No. of outcome Maternal age adjusted model Multivariable modela
% RR 95% CI RR 95% CI
> 3 nighttime waking instances
Sleep duration
 < 6 h 4948 118 2.4 1.04 0.85 1.26 1.08 0.89 1.32
 6 < 7 14,661 324 2.2 0.95 0.83 1.09 0.96 0.84 1.10
 7 < 8 25,136 584 2.3 Ref Ref
 8 < 9 18,302 466 2.6 1.10 0.98 1.24 1.09 0.96 1.23
 9 < 10 7494 209 2.8 1.23 1.05 1.43 1.20 1.02 1.40
 10< 3286 74 2.3 1.06 0.84 1.35 1.07 0.84 1.36
Bedtime
 21 < 24 49,995 1275 2.6 Ref Ref
 24 < 27 21,825 461 2.1 0.85 0.76 0.94 0.89 0.80 0.99
 Other 2007 39 1.9 0.83 0.61 1.14 0.90 0.65 1.23
> 1 waking instances lasting > 1 h
Sleep duration
 < 6 h 4948 411 8.3 1.54 1.38 1.71 1.49 1.34 1.66
 6 < 7 14,661 929 6.3 1.18 1.09 1.28 1.16 1.07 1.26
 7 < 8 25,136 1343 5.3 Ref Ref
 8 < 9 18,302 916 5.0 0.94 0.86 1.02 0.96 0.89 1.04
 9 < 10 7494 387 5.2 0.96 0.86 1.07 1.00 0.90 1.12
 10< 3286 224 6.8 1.24 1.08 1.42 1.25 1.09 1.44
Bedtime
 21 < 24 49,995 2460 4.9 Ref Ref
 24 < 27 21,825 1550 7.1 1.44 1.35 1.53 1.38 1.30 1.47
 Other 2007 200 10.0 1.99 1.73 2.28 1.92 1.67 2.21
< 8 h of sleep during the night (20:00–7:59)
Sleep duration
 < 6 h 4948 408 8.3 1.65 1.48 1.84 1.60 1.44 1.79
 6 < 7 14,661 872 6.0 1.21 1.11 1.31 1.19 1.09 1.29
 7 < 8 25,136 1233 4.9 Ref Ref
 8 < 9 18,302 804 4.4 0.89 0.82 0.98 0.92 0.84 1.00
 9 < 10 7494 319 4.3 0.86 0.77 0.97 0.90 0.80 1.02
 10< 3286 207 6.3 1.25 1.08 1.44 1.26 1.09 1.46
Bedtime
 21 < 24 49,995 2284 4.6 Ref Ref
 24 < 27 21,825 1361 6.2 1.37 1.28 1.46 1.31 1.22 1.40
 Other 2007 198 9.9 2.11 1.84 2.43 2.04 1.77 2.35
Falling asleep at 22:00 or later
Sleep duration
 < 6 h 4948 1363 27.6 1.39 1.32 1.46 1.33 1.26 1.40
 6 < 7 14,661 3359 22.9 1.17 1.13 1.22 1.15 1.10 1.19
 7 < 8 25,136 4898 19.5 Ref Ref
 8 < 9 18,302 3348 18.3 0.94 0.90 0.97 0.96 0.92 1.00
 9 < 10 7494 1183 15.8 0.80 0.76 0.85 0.84 0.79 0.89
 10< 3286 691 21.0 1.02 0.95 1.10 1.02 0.95 1.10
Bedtime
 21 < 24 49,995 8412 16.8 Ref Ref
 24 < 27 21,825 5935 27.2 1.60 1.55 1.65 1.53 1.48 1.58
 Other 2007 495 24.7 1.40 1.29 1.52 1.34 1.23 1.45
Frequency of crying at night (≥ 5 days/week)
Sleep duration
 < 6 h 4948 395 8.0 1.14 1.03 1.27 1.16 1.05 1.29
 6 < 7 14,661 1085 7.4 1.05 0.98 1.13 1.05 0.98 1.13
 7 < 8 25,136 1771 7.1 Ref Ref
 8 < 9 18,302 1345 7.4 1.05 0.98 1.12 1.05 0.98 1.12
 9 < 10 7494 548 7.3 1.04 0.95 1.15 1.05 0.96 1.15
 10< 3286 203 6.2 0.91 0.79 1.04 0.93 0.80 1.07
Bedtime
 21 < 24 49,995 3591 7.2 Ref Ref
 24 < 27 21,825 1609 7.4 1.03 0.98 1.09 1.05 0.99 1.11
 Other 2007 147 7.3 1.06 0.90 1.24 1.11 0.95 1.31
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CI confidence interval, RR risk ratio. Bold fonts showed the items of infant's sleep outcomes. 

aAdjusted for maternal age at delivery, smoking habits, alcohol consumption, pre-pregnancy body mass index, gestational age at birth, parity, infertility treatment, and infant sex.

Short sleep duration less than 6 h before pregnancy was associated with a higher risk of night waking for ≥ 1 h (RR = 1.49, 95% CI 1.34–1.66), sleeping for < 8 h at night (RR = 1.60, 95% CI 1.44–1.79), and falling sleep at 22:00 or later (RR = 1.33, 95% CI 1.26–1.40) in the offspring, compared to offspring of mothers who slept for 7–8 h. On the contrary, compared to offspring of mothers who slept for 7–8 h, the offspring of mothers who slept for more than 10 h before pregnancy were also at a higher risk of night waking for > 1 h (RR = 1.25, 95% CI 1.09–1.44) and sleeping for < 8 h at night (RR = 1.26, 95% CI 1.09–1.46). Compared to offspring of mothers who slept before midnight before pregnancy, offspring of mothers who slept after midnight had a higher risk of night waking for > 1 h (RR = 1.38, 95% CI 1.30–1.47), sleeping for < 8 h at night (RR = 1.31, 95% CI 1.22–1.40), and falling asleep at 22:00 or later (RR = 1.53, 95% CI 1.48–1.58).

In the sub-analysis limited to participants who slept for 7–9 h during pregnancy, we found similar associations between maternal sleep before pregnancy and the offspring’s sleep outcome (Supplemental Table 2). Maternal sleep for < 6 h increased the risk ratio of infants wakening for more than 1 h, sleeping for < 8 h during the night, and falling asleep at 22:00 or after. Maternal sleep for more than 10 h also increased the risk ratio of infants awakening for > 1 h and sleeping for < 8 h during the night. Maternal bedtime after midnight increased the risk ratio of infants awakening > 1 h, sleeping < 8 h, and falling asleep at 22:00 or later.

Maternal sleep during pregnancy and infant sleep (Table 3)

Table 3.

Association between sleep during pregnancy and infant sleep, Japan Environment and Children's Study (2011–2014).

No. of participants No. of outcome Maternal age adjusted model Multivariable modela
% RR 95% CI RR 95% CI
> 3 nighttime waking instances
Sleep duration
 < 6 h 3540 80 2.3 0.97 0.77 1.22 1.00 0.79 1.26
 6 < 7 11,099 244 2.2 0.93 0.80 1.08 0.94 0.81 1.09
 7 < 8 23,050 547 2.4 Ref Ref
 8 < 9 21,043 492 2.3 0.99 0.88 1.11 0.98 0.86 1.10
 9 < 10 10,394 288 2.8 1.19 1.03 1.37 1.16 1.01 1.34
 10< 4701 124 2.6 1.20 0.99 1.46 1.21 0.99 1.46
Bedtime
 21 < 24 54,403 1361 2.5 Ref Ref
 24 < 27 17,798 376 2.1 0.86 0.77 0.97 0.90 0.80 1.01
 Other 1626 38 2.3 0.98 0.71 1.35 1.02 0.74 1.40
Depth of sleep
 Very light 5054 172 3.4 1.73 1.46 2.04 1.74 1.47 2.06
 Light 30,977 888 2.9 1.45 1.31 1.61 1.44 1.30 1.60
 Normal 29,459 579 2.0 Ref Ref
 Deep 7007 117 1.7 0.85 0.70 1.04 0.86 0.70 1.04
 Very deep 1330 19 1.4 0.74 0.47 1.16 0.75 0.47 1.18
Feeling when waking up in the morning
 Very bad 1112 38 3.4 1.50 1.09 2.07 1.55 1.13 2.13
 Bad 15,106 425 2.8 1.19 1.06 1.32 1.19 1.07 1.33
 Normal 45,965 1102 2.4 Ref Ref
 Good 10,314 184 1.8 0.74 0.63 0.86 0.73 0.63 0.85
 Very good 1330 26 2.0 0.81 0.55 1.20 0.82 0.56 1.21
> 1 waking instances lasting > 1 h
Sleep duration
 < 6 h 3540 305 8.6 1.57 1.39 1.77 1.53 1.35 1.72
 6 < 7 11,099 697 6.3 1.15 1.05 1.26 1.13 1.03 1.24
 7 < 8 23,050 1254 5.4 Ref Ref
 8 < 9 21,043 1119 5.3 0.98 0.90 1.06 1.00 0.93 1.09
 9 < 10 10,394 550 5.3 0.97 0.88 1.07 1.01 0.92 1.12
 10< 4701 285 6.1 1.09 0.96 1.23 1.10 0.97 1.25
Bedtime
 21 < 24 54,403 2730 5.0 Ref Ref
 24 < 27 17,798 1321 7.4 1.47 1.38 1.57 1.41 1.32 1.51
 Other 1626 159 9.8 1.93 1.66 2.25 1.90 1.63 2.21
Depth of sleep
 Very light 5054 339 6.7 1.23 1.10 1.37 1.24 1.11 1.39
 Light 30,977 1794 5.8 1.07 1.00 1.14 1.08 1.01 1.15
 Normal 29,459 1604 5.4 Ref Ref
 Deep 7007 402 5.7 1.05 0.95 1.17 1.04 0.94 1.16
 Very deep 1330 71 5.3 0.97 0.77 1.23 0.96 0.76 1.21
Feeling when waking up in the morning
 Very bad 1112 84 7.6 1.32 1.07 1.63 1.30 1.06 1.61
 Bad 15,106 936 6.2 1.10 1.02 1.18 1.10 1.02 1.18
 Normal 45,965 2582 5.6 Ref Ref
 Good 10,314 546 5.3 0.94 0.86 1.03 0.94 0.86 1.03
 Very good 1330 62 4.7 0.83 0.65 1.06 0.82 0.64 1.05
< 8 h of sleep during the night (20:00–7:59)
Sleep duration
 < 6 h 3540 314 8.9 1.70 1.51 1.91 1.66 1.48 1.88
 6 < 7 11,099 714 6.4 1.25 1.14 1.36 1.23 1.12 1.34
 7 < 8 23,050 1184 5.1 Ref Ref
 8 < 9 21,043 906 4.3 0.84 0.77 0.91 0.86 0.79 0.93
 9 < 10 10,394 480 4.6 0.90 0.81 1.00 0.93 0.84 1.03
 10< 4701 245 5.2 1.00 0.87 1.14 1.01 0.88 1.16
Bedtime
 21 < 24 54,403 2508 4.6 Ref Ref
 24 < 27 17,798 1205 6.8 1.47 1.38 1.57 1.41 1.32 1.51
Other 1626 130 8.0 1.72 1.45 2.03 1.69 1.43 2.01
Depth of sleep
 Very light 5054 349 6.9 1.36 1.22 1.52 1.38 1.23 1.55
 Light 30,977 1640 5.3 1.05 0.98 1.13 1.07 1.00 1.14
 Normal 29,459 1477 5.0 Ref Ref
 Deep 7007 316 4.5 0.90 0.80 1.02 0.89 0.79 1.00
 Very deep 1330 61 4.6 0.91 0.71 1.17 0.90 0.70 1.15
Feeling when waking up in the morning
 Very bad 1112 92 8.3 1.63 1.34 2.00 1.62 1.33 1.98
 Bad 15,106 934 6.2 1.25 1.16 1.34 1.25 1.16 1.34
 Normal 45,965 2284 5.0 Ref Ref
 Good 10,314 477 4.6 0.93 0.85 1.03 0.93 0.84 1.02
 Very good 1330 56 4.2 0.84 0.65 1.09 0.83 0.64 1.08
Falling asleep at 22:00 or later
Sleep duration
 < 6 h 3540 1029 29.1 1.43 1.35 1.51 1.39 1.31 1.47
 6 < 7 11,099 2682 24.2 1.20 1.15 1.25 1.18 1.13 1.23
 7 < 8 23,050 4617 20.0 Ref Ref
 8 < 9 21,043 3720 17.7 0.88 0.85 0.92 0.90 0.87 0.94
 9 < 10 10,394 1740 16.7 0.83 0.79 0.87 0.86 0.82 0.91
 10< 4701 1054 22.4 1.07 1.01 1.14 1.08 1.02 1.15
Bedtime
 21 < 24 54,403 9402 17.3 Ref Ref
 24 < 27 17,798 5120 28.8 1.65 1.60 1.70 1.58 1.53 1.63
 Other 1626 320 19.7 1.12 1.01 1.24 1.10 0.99 1.21
Depth of sleep
 Very light 5054 1087 21.5 1.07 1.01 1.14 1.08 1.02 1.15
 Light 30,977 6213 20.1 1.01 0.98 1.04 1.02 0.99 1.05
 Normal 29,459 5882 20.0 Ref Ref
 Deep 7007 1404 20.0 1.00 0.95 1.06 0.99 0.94 1.04
 Very deep 1330 256 19.3 0.95 0.85 1.06 0.93 0.84 1.04
Feeling when waking up in the morning
 Very bad 1112 268 24.1 1.16 1.04 1.29 1.14 1.03 1.27
 Bad 15,106 3341 22.1 1.10 1.06 1.14 1.10 1.06 1.14
 Normal 45,965 9215 20.1 Ref Ref
 Good 10,314 1804 17.5 0.88 0.84 0.92 0.88 0.84 0.92
 Very good 1330 214 16.1 0.80 0.71 0.91 0.80 0.70 0.90
Frequency of crying at night (≥ 5 days/week)
Sleep duration
 < 6 h 3540 256 7.2 0.99 0.88 1.13 1.01 0.89 1.14
 6 < 7 11,099 848 7.6 1.04 0.96 1.13 1.05 0.97 1.13
 7 < 8 23,050 1695 7.4 Ref Ref
 8 < 9 21,043 1480 7.0 0.96 0.89 1.02 0.96 0.90 1.03
 9 < 10 10,394 761 7.3 1.00 0.92 1.09 1.00 0.92 1.09
 10< 4701 307 6.5 0.91 0.81 1.02 0.92 0.82 1.04
Bedtime
 21 < 24 54,403 3881 7.1 Ref Ref
 24 < 27 17,798 1351 7.6 1.07 1.01 1.14 1.08 1.02 1.15
 Other 1626 115 7.1 1.01 0.85 1.21 1.04 0.87 1.24
Depth of sleep
 Very light 5054 482 9.5 1.50 1.36 1.65 1.52 1.38 1.67
 Light 30,977 2470 8.0 1.25 1.18 1.32 1.25 1.18 1.32
 Normal 29,459 1882 6.4 Ref Ref
 Deep 7007 431 6.2 0.96 0.87 1.07 0.96 0.87 1.06
 Very deep 1330 82 6.2 0.97 0.78 1.20 0.97 0.79 1.20
Feeling when waking up in the morning
 Very bad 1112 111 10.0 1.43 1.20 1.72 1.46 1.22 1.75
 Bad 15,106 1294 8.6 1.21 1.13 1.28 1.21 1.14 1.29
 Normal 45,965 3275 7.1 Ref Ref
 Good 10,314 596 5.8 0.81 0.74 0.88 0.80 0.74 0.87
 Very good 1330 71 5.3 0.75 0.60 0.94 0.75 0.60 0.95
Open in a new tab

CI confidence interval, RR risk ratio. Bold fonts showed the items of infant's sleep outcomes. 

aAdjusted for maternal age at delivery, smoking habits, alcohol consumption, pre-pregnancy body mass index, gestational age at birth, parity, infertility treatment, and infant sex.

As for the analysis of maternal sleep before pregnancy, short or long sleep duration and sleeping after midnight during pregnancy were associated with a higher risk of some sleep outcomes. Infants whose mothers slept for less than 6 h during pregnancy tended to be awake for > 1 h at night (RR = 1.53, 95% CI 1.35–1.72), to sleep for < 8 h during night (RR = 1.66, 95% CI 1.48–1.88), and to sleep at 22:00 or later (RR = 1.39, 95% CI 1.31–1.47), compared to the infants whose mother slept for 7–8 h. On the contrary, compared to the offspring of mothers who slept for 7–8 h, offspring of mothers who slept for more than 10 h during pregnancy tended to sleep at 22:00 or later (RR = 1.08, 95% CI 1.02–1.15). Maternal bedtime after midnight during pregnancy was also associated with a higher risk of infants night waking for > 1 h (RR = 1.41, 95% CI 1.32–1.51), sleeping for < 8 h at night (RR = 1.41, 95% CI 1.32–1.51), falling asleep at 22:00 or later (RR = 1.58, 95% CI 1.53–1.63), and frequency of crying (RR = 1.08, 95% CI 1.02–1.15), compared to the group of maternal bedtime before midnight.

In the sub-analysis limited to the participants who slept for 7–9 h before pregnancy, we found similar associations between maternal sleep during pregnancy and infants’ sleep outcome (Supplemental Table 2). Maternal sleep for less than 6 h and for more than 10 h increased the risk ratio of falling asleep at 22:00 or after. Maternal bedtime after midnight increased the risk ratio of infants awakening for > 1 h at night, sleep < 8 h at night, and falling asleep at 22:00 or later.

Subjective items of sleep during pregnancy were also associated with the offspring’s sleeping problems. For example, maternal “very light” sleep was associated with a higher risk of 3 or more waking instances in a night (RR = 1.74, 95% CI 1.47–2.06), night waking for more than 1 h (RR = 1.24, 95% CI 1.11–1.39), sleeping for less than 8 h at night (RR = 1.38, 95% CI 1.23–1.55), sleeping at 22:00 or later (RR = 1.08, 95% CI 1.02–1.15), crying 5 days or more in a week (RR = 1.52, 95% CI 1.38–1.67), compared to the group of maternal “normal” sleep depth.

Maternal sleep and offspring developmental progress

We used the Japanese version of the Ages and Stages Questionnaire, third edition (J-ASQ-3), to evaluate the offspring’s development. There were no associations between sleep duration or bedtime, both before and during pregnancy, and abnormal J-ASQ-3 scores (Table 4). However, “good” and “very good” feelings when waking up during pregnancy were associated with a lower risk of abnormal J-ASQ-3 scores for any one of the five domains in a multivariable model (RR for good vs. normal = 0.86, 95% CI 0.81–0.91; RR for very good feeling vs. normal = 0.81, 95% CI 0.69–0.95) (Table 5), compared to the group of maternal “normal” feelings at waking up. Moreover, for the depth of sleep during pregnancy, “very deep” sleep decreased the risk of abnormal J-ASQ-3 scores (RR for very deep vs. normal = 0.83, 95% CI 0.71–0.98), compared to the group of maternal “normal” sleep depth.

Table 4.

Association between sleep before pregnancy and infant development, Japan Environment and Children's Study (2011–2014).

No. of participants No. of outcome Maternal age adjusted model Multivariable modela
% RR 95% CI RR 95% CI
Communication
Sleep duration
 < 6 h 4489 5 0.1 1.19 0.45 3.15 1.15 0.43 3.03
 6 < 7 13,427 18 0.1 1.40 0.75 2.61 1.32 0.71 2.47
 7 < 8 23,058 22 0.1 Ref Ref
 8 < 9 16,779 13 0.1 0.82 0.41 1.63 0.90 0.45 1.80
 9 < 10 6863 6 0.1 0.95 0.39 2.35 1.12 0.45 2.82
 10< 2975 3 0.1 1.29 0.38 4.31 1.42 0.42 4.78
Bedtime
 21 < 24 45,971 46 0.1 Ref Ref
 24 < 27 19,816 19 0.1 1.01 0.59 1.73 0.86 0.49 1.50
 Other 1804 2 0.1 1.33 0.32 5.51 1.39 0.33 5.79
Gross motor skills
Sleep duration
 < 6 h 4489 265 5.9 1.08 0.95 1.23 1.07 0.94 1.22
 6 < 7 13,427 832 6.2 1.12 1.03 1.22 1.11 1.02 1.20
 7 < 8 23,066 1264 5.5 Ref Ref
 8 < 9 16,775 902 5.4 0.99 0.91 1.07 1.02 0.93 1.10
 9 < 10 6861 327 4.8 0.89 0.79 1.01 0.94 0.84 1.06
 10< 2975 120 4.0 0.82 0.69 0.99 0.86 0.72 1.03
Bedtime
 21 < 24 45,972 2546 5.5 Ref Ref
 24 < 27 19,816 1073 5.4 1.01 0.95 1.09 0.97 0.90 1.05
 Other 1805 91 5.0 1.01 0.83 1.24 1.06 0.86 1.30
Fine motor skills
Sleep duration
 < 6 h 4489 252 5.6 1.01 0.88 1.15 1.02 0.90 1.17
 6 < 7 13,415 781 5.8 1.04 0.95 1.13 1.05 0.97 1.15
 7 < 8 23,063 1283 5.6 Ref Ref
 8 < 9 16,766 932 5.6 1.01 0.93 1.09 0.99 0.91 1.08
 9 < 10 6859 373 5.4 1.00 0.90 1.12 0.98 0.87 1.09
 10< 2974 141 4.7 0.95 0.80 1.12 0.93 0.79 1.10
Bedtime
 21 < 24 45,951 2623 5.7 Ref Ref
 24 < 27 19,811 1053 5.3 0.96 0.90 1.03 1.00 0.93 1.07
 Other 1804 86 4.8 0.92 0.74 1.13 0.94 0.76 1.16
Problems solving
Sleep duration
 < 6 h 4482 246 5.5 1.09 0.95 1.25 1.06 0.93 1.21
 6 < 7 13,404 726 5.4 1.08 0.98 1.18 1.04 0.95 1.14
 7 < 8 23,041 1151 5.0 Ref Ref
 8 < 9 16,757 831 5.0 1.00 0.92 1.09 1.05 0.96 1.15
 9 < 10 6848 343 5.0 1.03 0.91 1.16 1.12 1.00 1.26
 10 <  2973 141 4.7 1.04 0.88 1.24 1.10 0.93 1.31
Bedtime
 21 < 24 45,918 2321 5.1 Ref Ref
 24 < 27 19,785 1042 5.3 1.08 1.00 1.16 1.00 0.93 1.08
 Other 1802 75 4.2 0.89 0.71 1.12 0.90 0.72 1.13
Personal-social characteristics
Sleep duration
 < 6 h 4480 50 1.1 1.11 0.82 1.51 1.20 0.88 1.62
 6 < 7 13,402 142 1.1 1.05 0.85 1.29 1.12 0.91 1.37
 7 < 8 23,017 231 1.0 Ref Ref
 8 < 9 16,731 222 1.3 1.33 1.11 1.60 1.23 1.02 1.48
 9 < 10 6852 99 1.4 1.48 1.17 1.87 1.30 1.03 1.65
 10< 2971 34 1.1 1.27 0.89 1.82 1.18 0.82 1.69
Bedtime
 21 < 24 45,874 554 1.2 Ref Ref
 24 < 27 19,778 211 1.1 0.91 0.78 1.07 1.10 0.93 1.29
 Other 1801 13 0.7 0.66 0.38 1.14 0.72 0.41 1.24
Total (abnormal score for any 1 of the 5 domain)
Sleep duration
 < 6 h 4491 621 13.8 1.01 0.94 1.10 1.01 0.93 1.09
 6 < 7 13,432 1917 14.3 1.04 0.99 1.10 1.03 0.98 1.08
 7 < 8 23,070 3146 13.6 Ref Ref
 8 < 9 16,783 2218 13.2 0.98 0.93 1.03 0.99 0.95 1.05
 9 < 10 6865 874 12.7 0.96 0.89 1.03 0.99 0.92 1.06
 10< 2976 365 12.3 1.00 0.90 1.10 1.02 0.92 1.13
Bedtime
 21 < 24 45,987 6285 13.7 Ref Ref
 24 < 27 19,823 2645 13.3 1.01 0.97 1.05 0.98 0.94 1.03
 Other 1807 211 11.7 0.94 0.82 1.07 0.97 0.85 1.10
Open in a new tab

CI confidence interval, RR risk ratio. Bold fonts showed the items of the Ages and Stages Questionnaire. 

aAdjusted for maternal age at delivery, smoking habits, alcohol consumption, pre-pregnancy body mass index, gestational age at birth, parity, infertility treatment, and infant sex.

Table 5.

Association between sleep during pregnancy and infant development, Japan Environment and Children's Study (2011–2014).

No. of participants No. of outcome Maternal age adjusted model Multivariable modela
% RR 95% CI RR 95% CI
Communication
Sleep duration
 < 6 h 3186 5 0.2 1.32 0.51 3.43 1.29 0.49 3.35
 6 < 7 10,130 12 0.1 0.97 0.49 1.93 0.93 0.47 1.86
 7 < 8 21,181 26 0.1 Ref Ref
 8 < 9 19,275 13 0.1 0.55 0.28 1.07 0.60 0.30 1.16
 9 < 10 9528 10 0.1 0.88 0.42 1.83 0.99 0.47 2.08
 10< 4291 1 0.0 0.22 0.03 1.65 0.24 0.03 1.80
Bedtime
 21 < 24 50,034 48 0.1 Ref Ref
 24 < 27 16,083 18 0.1 1.23 0.72 2.12 1.07 0.61 1.86
 Other 1474 1 0.1 0.78 0.11 5.64 0.82 0.11 5.95
Depth of sleep
 Very light 4563 4 0.1 0.81 0.28 2.30 0.82 0.29 2.35
 Light 28,285 24 0.1 0.78 0.45 1.33 0.79 0.46 1.35
 Normal 27,044 29 0.1 Ref Ref
 Deep 6465 6 0.1 0.88 0.37 2.12 0.86 0.36 2.06
 Very deep 1234 4 0.3 3.16 1.11 8.98 3.01 1.06 8.55
Feeling when waking up in the morning
 Very bad 991 3 0.3 3.41 1.06 10.99 3.38 1.05 10.88
 Bad 13,634 15 0.1 1.13 0.63 2.04 1.12 0.62 2.02
 Normal 42,197 42 0.1 Ref Ref
 Good 9530 4 0.0 0.41 0.15 1.16 0.40 0.14 1.11
 Very good 1239 3 0.2 2.41 0.75 7.75 2.27 0.70 7.33
Gross motor skills
Sleep duration
 < 6 h 3186 191 6.0 1.06 0.92 1.23 1.06 0.92 1.23
 6 < 7 10,130 613 6.1 1.06 0.97 1.17 1.05 0.95 1.15
 7 < 8 21,184 1203 5.7 Ref Ref
 8 < 9 19,275 1020 5.3 0.94 0.86 1.02 0.96 0.89 1.04
 9 < 10 9526 497 5.2 0.94 0.85 1.04 0.99 0.89 1.09
 10< 4292 186 4.3 0.85 0.73 0.99 0.88 0.76 1.03
Bedtime
 21 < 24 50,037 2778 5.6 Ref Ref
 24 < 27 16,079 842 5.2 0.98 0.91 1.05 0.93 0.86 1.01
 Other 1477 90 6.1 1.16 0.95 1.43 1.19 0.97 1.46
Depth of sleep
 Very light 4564 258 5.7 1.00 0.88 1.13 1.02 0.90 1.16
 Light 28,288 1521 5.4 0.95 0.89 1.02 0.96 0.89 1.03
 Normal 27,045 1512 5.6 Ref Ref
 Deep 6463 355 5.5 0.99 0.89 1.11 0.99 0.88 1.10
 Very deep 1233 64 5.2 0.95 0.75 1.21 0.96 0.75 1.22
Feeling when waking up in the morning
 Very bad 991 48 4.8 0.95 0.72 1.25 0.97 0.73 1.28
 Bad 13,636 762 5.6 1.04 0.96 1.13 1.05 0.97 1.13
 Normal 42,197 2306 5.5 Ref Ref
 Good 9531 529 5.6 1.00 0.92 1.10 1.00 0.91 1.09
 Very good 1238 65 5.3 0.95 0.75 1.21 0.93 0.73 1.17
Fine motor skills
Sleep duration
 < 6 h 3184 180 5.7 1.00 0.85 1.16 1.00 0.86 1.16
 6 < 7 10,124 587 5.8 1.01 0.92 1.11 1.03 0.93 1.13
 7 < 8 21,178 1210 5.7 Ref Ref
 8 < 9 19,265 1068 5.5 0.97 0.90 1.06 0.96 0.89 1.04
 9 < 10 9524 492 5.2 0.93 0.84 1.02 0.90 0.82 1.00
 10< 4291 225 5.2 1.01 0.88 1.16 1.01 0.88 1.16
Bedtime
 21 < 24 50,017 2841 5.7 Ref Ref
 24 < 27 16,074 838 5.2 0.95 0.88 1.02 0.97 0.90 1.05
 Other 1475 83 5.6 1.04 0.84 1.29 1.05 0.85 1.29
Depth of sleep
 Very light 4558 251 5.5 0.96 0.84 1.09 0.94 0.82 1.06
 Light 28,280 1577 5.6 0.97 0.91 1.04 0.97 0.90 1.04
 Normal 27,035 1532 5.7 Ref Ref
 Deep 6462 351 5.4 0.97 0.87 1.08 0.98 0.88 1.10
 Very deep 1231 51 4.1 0.75 0.57 0.98 0.76 0.58 1.00
Feeling when waking up in the morning
 Very bad 990 58 5.9 1.09 0.85 1.41 1.08 0.84 1.39
 Bad 13,635 829 6.1 1.09 1.01 1.17 1.08 1.00 1.17
 Normal 42,175 2396 5.7 Ref Ref
 Good 9528 425 4.5 0.78 0.70 0.86 0.78 0.71 0.86
 Very good 1238 54 4.4 0.76 0.58 0.99 0.78 0.60 1.01
Problems solving
Sleep duration
 < 6 h 3182 182 5.7 1.09 0.94 1.27 1.07 0.92 1.25
 6 < 7 10,115 525 5.2 0.99 0.89 1.09 0.96 0.87 1.07
 7 < 8 21,161 1105 5.2 Ref Ref
 8 < 9 19,253 970 5.0 0.97 0.89 1.05 1.01 0.93 1.10
 9 < 10 9508 438 4.6 0.90 0.81 1.01 0.96 0.86 1.07
 10< 4286 218 5.1 1.07 0.92 1.23 1.12 0.97 1.29
Bedtime
 21 < 24 49,976 2544 5.1 Ref Ref
 24 < 27 16,057 817 5.1 1.03 0.96 1.11 0.96 0.89 1.04
 Other 1472 77 5.2 1.08 0.86 1.34 1.09 0.88 1.36
Depth of sleep
 Very light 4557 211 4.6 0.84 0.73 0.97 0.85 0.74 0.98
 Light 28,256 1406 5.0 0.91 0.85 0.97 0.92 0.86 0.99
 Normal 27,001 1463 5.4 Ref Ref
 Deep 6458 312 4.8 0.90 0.80 1.02 0.89 0.79 1.01
 Very deep 1233 46 3.7 0.70 0.53 0.94 0.70 0.53 0.93
Feeling when waking up in the morning
 Very bad 990 63 6.4 1.28 1.01 1.64 1.29 1.01 1.64
 Bad 13,620 737 5.4 1.05 0.97 1.14 1.05 0.97 1.14
 Normal 42,133 2204 5.2 Ref Ref
 Good 9525 390 4.1 0.77 0.70 0.86 0.77 0.69 0.85
 Very good 1237 44 3.6 0.67 0.50 0.90 0.66 0.50 0.89
Personal-social characteristics
Sleep duration
 < 6 h 3182 40 1.3 1.27 0.91 1.77 1.33 0.95 1.85
 6 < 7 10,110 105 1.0 1.04 0.82 1.31 1.10 0.87 1.38
 7 < 8 21,141 211 1.0 Ref Ref
 8 < 9 19,222 259 1.4 1.36 1.13 1.63 1.27 1.06 1.53
 9 < 10 9511 112 1.2 1.21 0.96 1.52 1.08 0.86 1.36
 10< 4287 51 1.2 1.31 0.97 1.78 1.24 0.92 1.69
Bedtime
 21 < 24 49,936 584 1.2 Ref Ref
 24 < 27 16,045 173 1.1 0.95 0.80 1.13 1.12 0.94 1.33
 Other 1472 21 1.4 1.29 0.83 1.98 1.29 0.84 1.99
Depth of sleep
 Very light 4553 57 1.3 1.01 0.76 1.33 0.95 0.72 1.26
 Light 28,224 318 1.1 0.91 0.78 1.06 0.89 0.76 1.03
 Normal 26,991 331 1.2 Ref Ref
 Deep 6451 59 0.9 0.75 0.57 0.99 0.79 0.60 1.04
 Very deep 1234 13 1.1 0.88 0.51 1.53 0.92 0.53 1.60
Feeling when waking up in the morning
 Very bad 991 17 1.7 1.59 0.99 2.57 1.58 0.98 2.55
 Bad 13,608 179 1.3 1.17 0.98 1.38 1.16 0.98 1.38
 Normal 42,104 482 1.1 Ref Ref
 Good 9514 82 0.9 0.75 0.59 0.94 0.76 0.60 0.96
 Very good 1236 18 1.5 1.26 0.79 2.01 1.32 0.82 2.10
Total (abnormal score for any 1 of the 5 domain)
Sleep duration
 < 6 h 3187 460 14.4 1.04 0.95 1.14 1.04 0.95 1.13
 6 < 7 10,132 1443 14.2 1.02 0.96 1.08 1.01 0.95 1.07
 7 < 8 21,191 2957 14.0 Ref Ref
 8 < 9 19,283 2547 13.2 0.95 0.90 1.00 0.97 0.92 1.02
 9 < 10 9531 1217 12.8 0.93 0.88 0.99 0.96 0.90 1.02
 10< 4293 517 12.0 0.95 0.87 1.03 0.98 0.89 1.07
Bedtime
 21 < 24 50,054 6822 13.6 Ref Ref
 24 < 27 16,086 2118 13.2 1.00 0.95 1.04 0.97 0.93 1.02
 Other 1477 201 13.6 1.05 0.92 1.20 1.07 0.94 1.22
Depth of sleep
 Very light 4564 601 13.2 0.93 0.86 1.01 0.94 0.87 1.02
 Light 28,297 3794 13.4 0.95 0.91 0.99 0.96 0.92 1.00
 Normal 27,054 3762 13.9 Ref Ref
 Deep 6468 845 13.1 0.95 0.89 1.02 0.95 0.88 1.02
 Very deep 1234 139 11.3 0.83 0.70 0.97 0.83 0.71 0.98
Feeling when waking up in the morning
 Very bad 991 133 13.4 1.04 0.89 1.22 1.05 0.89 1.23
 Bad 13,641 1947 14.3 1.06 1.01 1.11 1.06 1.01 1.11
 Normal 42,211 5779 13.7 Ref Ref
 Good 9535 1143 12.0 0.87 0.82 0.92 0.86 0.81 0.91
 Very good 1239 139 11.2 0.81 0.69 0.95 0.81 0.69 0.95
Open in a new tab

CI confidence interval, RR risk ratio.  Bold fonts showed the items of the Ages and Stages Questionnaire.

aAdjusted for maternal age at delivery, smoking habits, alcohol consumption, pre-pregnancy body mass index, gestational age at birth, parity, infertility treatment, and infant sex.

Discussion

This study investigated whether maternal sleep before and during pregnancy was associated with sleeping or developmental problems in 1-year-old infants, using data from a nationwide large-scale cohort study in Japan. The present study showed that maternal short or long sleep and bedtime after midnight, both before and during pregnancy, increased the risk ratio of the offspring’s sleeping problems at 1 year of age. The sub-analysis limited to participants with adequate sleep durations showed that maternal sleep pattern both before and during pregnancy was associated with the infants’ sleep outcomes. In addition, maternal subjective deep sleep and good mood at waking up during pregnancy were inversely associated with the infants’ sleep problems and the J-ASQ abnormal scores.

In this study, the participants tended to sleep longer and go to bed earlier during pregnancy than they did before pregnancy. In Japan, many women still stop working due to pregnancy or take maternity leave during late pregnancy. For that reason, sleep duration and bedtime might improve during pregnancy.

Sleep cycle develops from the fetal period13. Animal studies have shown that the circadian rhythm is affected by maternal life rhythms via endogenous substances such as melatonin14,15. Animal studies have also reported that exposure to sleep deprivation or artificial disappearance of light–dark cycle during pregnancy affects the offspring’s circadian rhythm abnormality and abnormal behavioral pattern16,17. In this study, mother’s short sleep and late bedtime were associated with the offspring’s sleeping problems, in part, because of the influence of maternal life rhythm during the fetal period.

In addition, it is considered that postpartum sleep pattern would partly correlate with sleep pattern before or during pregnancy. The study of 18-month-old twin infants reported that the genetic effect on sleep duration was 30.8% and the environmental effect was 64.1%18. The association between sleep before or during pregnancy and infant sleeping problems may be influenced via life rhythm after childbirth.

Subjective sleep quality was associated not only with infants’ sleep problem but also with the risk of abnormal ASQ scores. Subjective light sleep and bad mood upon wakening may reflect maternal SDB or depression19,20. Furthermore, it has been reported that both of these factors are related to the offspring’s development10,21. One potential factor explaining the association between maternal sleep and the offspring’s outcomes is inflammation. SDB and maternal depression increase inflammatory cytokine levels22–24; maternal inflammation during pregnancy can cause developmental disorders25,26. In addition, maternal SDB may affect the offspring’s development via low birth weight, which has been reported to be associated with neurodevelopment27,28. Interventions in maternal SDB and depression during pregnancy may improve subjective sleep quality and subsequent offspring sleep and development.

We have previously reported that maternal sleep habits, such as short sleep and late bedtime, before and during pregnancy, increased the risk ratio of long sleep duration during the day, bad mood, frequency of crying for a long time, and intense crying in 1-month-old offspring12. We further showed the association between maternal unsuitable sleep habits and the offspring’s non-desirable sleep habits as lasting even 1 year after birth. It is expected that children’s sleep and development will be influenced more by factors after birth than by prenatal ones. Therefore, it is important to clarify how long maternal sleep habits both before and during pregnancy are related to offspring’s sleep and developmental progression and to verify whether an intervention of maternal sleep, at any time point, improves offspring’s sleep and developmental outcomes.

This study was not without limitations. Because the present study was an observational study, confounding factors, such as parental life rhythm, that were not part of our evaluations might have been present. Moreover, information regarding both maternal sleep habits and infant’s outcomes was collected using a self-reported questionnaire, and thus, it had a risk of bias, such as a recall bias. The questions about maternal and infant sleep have not been previously validated. For example, we used the frequency of infant’s night crying as outcome, but we could not get the intended information about the duration and reason for the infant crying. Thus, there could be some bias, such as reporting bias. Additionally, about 13% of the participants were excluded from the analysis due to lack of information about exposure, covariates, and outcomes, and this group tended to be younger and with more smokers than the mothers who responded. This may be an added bias. In addition, because each association between maternal sleep and outcomes was tested separately, multiple testing may be a limitation. However, a strong point of this study is that our results were derived from large-scale nationwide data. To the best of our knowledge, there is no other study of this size on how maternal sleep during pregnancy correlates with offspring sleep behavior.

In conclusion, maternal short or long sleep duration and late bedtime, both before and during pregnancy, may increase sleeping problems such as late bedtime, awakening during night, and short sleep in 1-year-old offspring. Additionally, subjective maternal deep sleep and good mood at waking up during pregnancy decreased the risk ratio of infants’ sleeping problem and the ASQ abnormal scores.

Methods

Research ethics

The study protocol was approved by the Ministry of Environment’s Institutional Review Board on Epidemiological Studies and by the Ethics Committee of all participating institutions: the National Institute for Environmental Studies that leads the Japan Environment and Children’s Study (JECS), the National Center for Child Health and Development, Hokkaido University, Sapporo Medical University, Asahikawa Medical College, Japanese Red Cross Hokkaido College of Nursing, Tohoku University, Fukushima Medical University, Chiba University, Yokohama City University, University of Yamanashi, Shinshu University, University of Toyama, Nagoya City University, Kyoto University, Doshisha University, Osaka University, Osaka Medical Center and Research Institute for Maternal and Child Health, Hyogo College of Medicine, Tottori University, Kochi University, University of Occupational and Environmental Health, Kyushu University, Kumamoto University, University of Miyazaki, and University of Ryukyu. Written informed consent was obtained from all participants. All methods were performed in accordance with the approved guidelines.

Study participants

The data used in this study were obtained from the JECS, an ongoing large-scale cohort study. The JECS elucidated environmental factors that are associated with children’s health and development, and was designed to follow women through their pregnancy until their newborns grow up to be 13 years old. The participants were recruited between 2011 and 2014 from 15 regions throughout Japan, and the follow-up was mainly conducted via a self-administered questionnaire. The detailed protocol has been reported elsewhere29. The baseline profiles of participants of the JECS have been reported previously30. Participants answered a questionnaire about lifestyle and behavior twice during pregnancy. The questionnaire answered at recruitment was M-T1 and answered later during mid and late pregnancy was M-T2. The mean gestational weeks (SD, 5–95 percentile) at the time of answering M-T1 and M-T2 were 16.4 (8.0, 9–29) and 27.9 (6.5, 25–35) weeks, respectively. Participants also answered a questionnaire about their offspring 1 year after delivery (C-1y).

We excluded cases of multiple pregnancies (n = 949), preterm or post-term deliveries (before 37 weeks or after 42 weeks of gestation) (n = 4184), and congenital anomalies identified before 1 month of age (n = 3553). These factors are thought to be associated with infant development. For women who participated in the JECS study multiple times, data from the second and subsequent participations were excluded (n = 5647). In addition, we excluded cases for which information required for analysis was not available: miscarriage or stillbirth (n = 3676), missing information on maternal age at delivery (n = 7), lack of information about covariates (n = 450), incomplete information on maternal sleep at both M-T1 and M-T2 (n = 3376), missing responses to all questions about children’s sleep habits and developmental progress at C-1y (n = 7393).

The remaining 73,827 participants were included in the analysis (Fig. 1). To determine the risk of potential bias due to missing data, we compared the background characteristics between the population analyzed and the population excluded from analysis due to a lack of information about covariates and non-response to any questions about maternal sleep or children’s sleep and development (Supplemental Table 3). The group excluded from the analysis had more participants who were less than 25 years old and had smoking habits, lower educational background, and lower household income.

Figure 1.

Figure 1

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Flow chart representing the study population. MT1 questionnaire administered at recruitment, MT2 questionnaire administered during mid- or late-pregnancy, ASQ the Ages and Stages Questionnaire.

Maternal sleep

The categorization of maternal sleep was done as in our previous research12.

In the M-T1 questionnaire, participants were asked about their awakening time and bedtime before pregnancy. We calculated the sleep duration of participants and divided the participants into six groups according to sleep time: < 6 h, 6–7 h, 7–8 h (reference), 8–9 h, 9–10 h, and > 10 h. Participants were also divided by bedtime: 9.00 p.m. to midnight (reference), midnight to 3.00 a.m., and others (sleep before 9.00 p.m. or after 3.00 a.m.). The bedtime for more than 95% of the analyzed subjects was between 21:00 and 27:00. Since the mode of bedtime was between 22:00 and 24:00, we further divided the participants by bedtime 24:00.

In the M-T2 questionnaire, participants were asked about their usual awakening time and bedtime in the last month. The participants were divided into groups as described above for M-T1. Furthermore, the M-T2 questionnaire included two additional questions regarding sleep quality. One was “How would you rate your average depth of sleep during the past month?” The other one was “How would you rate your overall feeling when waking up in the morning, during the past month?” The answers to both questions were scored on a 1–5 scale, representing very light/bad, relatively light/bad, normal (reference), relatively deep/good, and very deep/good, respectively. Both of these questionnaires (M-T1 and M-T2) have not been previously validated.

Outcome 1: offspring’s sleeping problems

One year after delivery, information on infant sleep habits and crying at night was collected via a parent-reported questionnaire (C-1y). The participants answered their infant sleep time in the last 24 h in 30-min increments. They were also asked whether their children cried at night over the last month, and if so, the frequency (“rarely”, “1–3 times in a month”, “1–2 times in a week”, “3–4 times in a week”, “5 times in a week or more”). The questionnaires used for this outcome have not been previously validated. In this analysis, we focused on five points. First, from the responses regarding the infant’s sleep the day before, we determined the number of nocturnal awakenings. A previous study reported that the upper limit of the number of awakenings during the night is 2.5 for 1-year-old infants31; as such, we defined ≥ 3 awakenings as too many. Second, we analyzed whether the infants awoke more than once and whether they stayed awake for more than 1 h during the night. Third, we analyzed the duration of nocturnal sleep (from 20:00 to 07:59). We regarded less than 8 h of sleep as unusual. Fourth, we collected information regarding the infants’ bedtime. Based on previous studies32,33, we defined bedtime after 22:00 as too late. Fifth, we analyzed nocturnal crying frequency during the past month. If the mother answered that her infant awoke and cried during the night, and that the frequency of crying at night was more than five times per week, we defined the case as “crying at night”.

Offspring’s development

We used the J-ASQ-3 to evaluate offspring’s development. The C-1y questionnaire included a J-ASQ-3 assessment. J-ASQ-3 captures any developmental delay in five domains: communication, gross motor skills, fine motor skills, problem solving, and personal–social characteristics. The answer to each question is one of the following: “yes,” “sometimes,” or “not yet.” Scores are 10, 5, and 0 points, respectively. Each J-ASQ-3 domain was composed of six questions, and the total score ranged from 0 to 60. Higher scores were defined as more developed, and the cutoff points for every domain in the Japanese version were determined by a previous study34. We defined outcomes by whether the score was less than the determined cut-off point of each J-ASQ-3 domain and whether the score was less than the cutoff point of any one of the five J-ASQ-3 domains.

Covariates

Information about maternal age at delivery, smoking habits, alcohol consumption, pre-pregnancy body mass index (BMI), parity, gestational age at birth, infertility treatment, and infant sex, was collected via self-administered questionnaires and/or medical records. These selected covariates were reported as risk factors for developmental disorders35–37.

Statistical analyses

We used a log-binominal regression model to explore the association of maternal sleep with each outcome and to estimate the RRs of each outcome and 95% CIs. We initially adjusted for maternal age at delivery and then further adjusted for smoking habits (never smoked, ex-smokers who quit before pregnancy, smokers during early pregnancy), alcohol consumption (never drinkers, ex-drinkers who quit before pregnancy, drinkers during early pregnancy), pre-pregnancy BMI (< 18.5, 18.5–24.9, ≥ 25.0 kg/m2), parity (0, ≥ 1), infertility treatment (no ovulation stimulation/artificial insemination by sperm from husband, assisted reproductive technology), gestational age at birth (37–38, 39–41 weeks), and infant sex (boys, girls). In this study, we did not actively complete any missing data, and all analysis was limited to data from those participants who provided complete information for exposures, outcomes, and covariates. In addition, we performed a sub-analysis twice to evaluate which maternal sleep, the one before or one during pregnancy, impacts the infant’s sleep outcome. In the first sub-analysis, we limited it to the participant groups with adequate sleep duration of 7–9 h during pregnancy and investigated the association between maternal sleep before pregnancy and infant’s sleep. We limited the second analysis to the participant groups with sleep duration of 7–9 h before pregnancy and examined the association between maternal sleep during pregnancy and infant’s sleep.

These statistical analyses were almost the same as those used in our previous study12.

In this study, we used a fixed dataset “jecs-an-20180131,” which was released in March 2018. Stata version 15 (StataCorp LP, College Station, TX, USA) was used for all analyses.

Supplementary Information

Supplementary Information. (60.2KB, docx)

Acknowledgements

We would like to express our gratitude to all the participants of this study and all the individuals involved in data collection. The idea of this work was obtained from other works supported by RIKEN Healthcare and Medical Data Platform Project and JSPS KAKENHI (Grant numbers: JP16H01880, JP16K13072, JP18H00994, JP18H03388).

Author contributions

Study conception and design: S.M. Statistical analyses: T.M. Drafting of the manuscript and approval of the initial content: K.N., S.M., and T.M. Critical revision of the manuscript for important intellectual content and manuscript review: K.N., T.M., S.M., M.O., K.K. (Kiyoko Kato), M.S. (Masafumi Sanefuji), E.S., M.T., M.S. (Masayuki Shimono), T.K., S.O., K.K. (Koichi Kusuhara), and JECS Group members.

Funding

The Japan Environment and Children’s Study was funded by the Ministry of the Environment, Japan. The findings and conclusions of this article are solely the responsibility of the authors and do not represent the official views of the Ministry of the Environment.

Competing interests

The authors declare no competing interests.

Footnotes

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

These authors contributed equally: Kazushige Nakahara and Takehiro Michikawa.

A list of authors and their affiliations appears at the end of the paper.

Contributor Information

Seiichi Morokuma, Email: morokuma@med.kyushu-u.ac.jp.

the Japan Environment and Children’s Study Group:

Michihiro Kamijima, Shin Yamazaki, Yukihiro Ohya, Reiko Kishi, Nobuo Yaegashi, Koichi Hashimoto, Chisato Mori, Shuichi Ito, Zentaro Yamagata, Hidekuni Inadera, Takeo Nakayama, Hiroyasu Iso, Masayuki Shima, Youichi Kurozawa, Narufumi Suganuma, and Takahiko Katoh

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-021-91271-7.

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