Methodology

The systematic review is structured according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 protocol and checklist.12 The protocol of this review has been registered with the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42021254301).

2.1 Search strategy

We searched the following electronic database sources for relevant articles according to the search strategy: Ovid MEDLINE, PubMed, SCOPUS, EMBASE and CENTRAL for peer-reviewed articles published until 31st December 2021. The following combination of Medical Subject Heading (MeSH) terms and keywords was used: (‘fasting’ or ‘intermittent fasting’ or ‘diet restriction’ or ‘Ramadan’ or ‘Muslim’ or ‘Islam’) and (‘fetal movement’ or ‘fetal wellbeing’ or ‘fetal development’ or ‘biophysical profile’) and (‘pregnancy’ or ‘pregnant women’ or ‘expectant mother’). Search was restricted to ‘human studies’ and English language where possible. The searches conducted in all e-databases are provided as Supplementary Table S1.

2.2 Study selection

The article selection process was facilitated using Covidence software.13 The articles obtained from the database searches were imported to Covidence, where duplicated records were deleted. A two-stage screening process was utilized in our study selection process. At the first screening stage, titles and abstracts were screened according to inclusion and exclusion criteria. Potential articles were included, and studies that cannot be excluded based on title/abstract underwent the second stage of screening. Full texts were retrieved and again screened in the second stage according to inclusion and exclusion criteria.
All case-control studies and observational cohorts (prospective or retrospective) that reported on fetal movements of pregnant women who underwent RF for at least 1 day at any point of time during pregnancy are included. For the purpose of this review, fasting is defined as RF which is an Islamic rule that requires Muslims to have total abstinence from food and water from sunrise to sunset for a consecutive period of 29-30 days.14 On the other hand, fetal movement is defined as the fluttering movements of a fetus perceived by a pregnant woman at around 20 weeks of pregnancy, which indicates the fetus’s growth in size and strength.15
Grey literature, conference proceedings, theses, reviews, non-peer-reviewed monographs, books, book chapters, study protocols, case studies, and cross-sectional studies were excluded. We excluded studies conducted in vitro or in vivo, single-armed or cohort studies with no comparator group, and studies where fasting duration during Ramadan is less than a day.
Two researchers independently reviewed, discussed, and agreed upon the eligibility of all studies. A third researcher resolved any conflict in the agreement between the researchers. We did a manual search of the reference lists of the included articles for other relevant studies not found in the database search.

2.3 Data extraction and synthesis

Eligible papers are categorized in a Google sheet to provide clarity. The study origin, the mean age of participants, study setting, trimester, type of fasting, outcome reported, and most important findings are extracted from the final eligible papers. As this is a qualitative synthesis, the findings are presented as narratives, including tables and figures to aid in data presentation where appropriate.

2.4 Quality assessment

Two researchers conducted quality assessment for the quantitative studies using the Newcastle-Ottawa Scale (NOS)16checklist independently. Similar to the screening process, a third researcher acted as a conflict resolver.

Results

3.1 Study selection and characteristics

We identified 1,366 records through electronic database searches and 8 records through manual searching. A total of 216 duplicate records were removed, and subsequently, the titles and abstracts of 1,158 records were screened for inclusion. The full texts of 44 articles were reviewed for eligibility, and finally, 18 studies were included in the review (Supplementary Table S2). The study selection process is summarized in a PRISMA 2020 flow diagram (Figure 1).
[insert Figure 1]
The majority of the studies were conducted in Turkey (33.3%), followed by Iran (16.7%), Canada (11.1%) and Saudi Arabia (11.1%) (Table 1). Sixteen studies were published within the last decade. Two-thirds of the studies were of cohort designs (prospective or retrospective), and all involved RF. Most of the studies were conducted across all trimesters (38.9%) or in the second and third trimesters (27.8%). A total of 3,213,070 samples were reported collectively in the included studies, with mostly the mean maternal age ranging from 27 and 30 years (50.0%).
[insert Table 1]
According to NOS, the median quality score was 5 (range: 4-6) for case-control studies and 7 (range: 6-9) for cohorts (Table 2). Overall, eleven studies (61.1%) scored 7 and above, indicating high quality, while the other seven (38.9%) scored 4–6, indicating intermediate quality.

3.2 Effect of fasting on neonatal outcomes.

Table 3 presents the summary of outcomes that were reported by the studies included in this review. Thirteen studies (72.2%) reported the effect of fasting on neonatal weight, followed by six studies (33.3%) on amniotic fluid index. Five studies (27.8%) reported on biparietal diameter, estimated fetal body weight, head circumference and fetal femur length, while gestational age at delivery, preterm birth/delivery and length were reported by four studies (22.2%). Fewer studies reported other outcomes like abdominal circumference, biophysical profile, APGAR score and stillbirth.
[insert Table 3]

3.3 Neonatal weight

Only one study found a significant association between maternal fasting and neonatal weight.21 The authors reported significantly lower birth weight in neonates of Ramadan-fasted women during the second and third trimesters than the control group (3094±467g vs.202±473 g; P=0.024). Savitri et al.’s study22 among women who fasted in their first trimester showed a potential reduction in the birthweight of newborns than of non-fasting mothers. However, the results were insignificant (-198 g, 95 % CI -447–51, P=0.12).22

3.4 Amniotic fluid index (AFI)

The results on AFI were not statistically significant in all but two studies.24,26 Karateke et al.,25which presented AFI findings for both second and third trimesters fasting respectively, determined a significant reduction in AFI for second trimester fasting only (11.4(9.8-14.1)cm vs 16.2(12.6-18.3)cm, P=0.02). Seckin and colleagues23 noted a significant decrease in AFI in the fasting group for third trimester fasting (20.1±11.2cm vs11.5±6.4cm,P<0.001). They concluded that maternal fasting reduced the interval for development of oligohydramnios.
Despite showing no significant difference in AFI increase between fasting and non-fasting groups, Sakar et al.’s32demonstrated a significantly lower increase in AFI of fasting group, potentially due to higher incidence of dehydration among fasting group, attributed by longer daytime above 17 hours and high temperatures between 36°C to 43°C.

3.5 Increase in biparietal diameter (BPD)

Only one study showed a significant association between both variables.32 Sakar and colleagues32noted that increase in BPD was significantly different from initial measurements between fasting and non-fasting groups (9.69±3.07mm vs10.74±1.99mm,P=0.041) for pregnant women in their second and third trimesters. Other than Sakar et al.,32 all four remaining studies reported insignificant findings. Except for Dikensoy et al.,29,30 three other studies demonstrated that increase in BPD was greater in non-fasting control groups.23,25,31

3.6 Increase in estimated fetal body weight (EFBW)

Findings correlating the increase in EFBW and fasting were not significant in all articles (P>0.05). In Karateke’s25 and Sakar’s32 studies, there were expected greater increases in EFBW in non-fasting groups, compared to the fasting groups.25,32 However, the inverse was true for the three remaining studies.23,29,30,31

3.7 Increase in fetal femur length (FL)

Only one study showed a significant association between fasting and increase in fetal FL. Sakar et al.’s32 study showed a significantly more significant increase in fetal FL in the non-fasting control group than with second and third trimesters fasting (9.98±1.86mm vs8.57±2.56mm, P=0.002). As for the remaining articles with insignificant findings, three studies23,29,30,31 noted that the increase in fetal FL was lesser in the control groups than in the study groups, unlike in Karateke et al.,25 which reported a larger increase in fetal FL in the non-fasting control group.

3.8 Gestational age at delivery

Only Alwasel’s study19 found a significant association between RF and gestational age at delivery. The author reported that girls whose mothers were in their second trimester of pregnancy during the fasting month endured a shorter gestation period than girls who were not in utero during Ramadan (39.4weeks vs39.8weeks,P=0.04). The differences in gestational age at delivery for other trimesters and boys in general, were not statistically significant.
In two other studies,21,23 mothers who fasted during pregnancy also experienced a shorter gestational period than pregnant mothers who did not fast. Contrarily, one study26noted that pregnant women fasted during their third trimester had a longer gestational age at delivery than their non-fasting counterparts.

3.9 Increase in length, head circumference (HC), and abdominal circumference (AC)

In Sakar and colleagues’s study32, second and third trimesters’ fasting had significant increase on HC in the control group than study group (39.12±7.42cm vs 35.12±12.22cm, P=0.046). However, the other articles6,19,28 showed no significant between fasting and an increase in HC. Alwasel et al.19 also noted boys’ HC in utero were generally larger than girls’ during fasting.
Only one study19 showed the length of boys whose mothers were in their second trimesters of pregnancy was significantly greater than boys who were not in utero during Ramadan (52.3cm vs 51.1cm, P=0.005). However, no significant association was found between fasting and babies’ height in three other studies.6,27,28
All three articles reporting on AC indicated insignificant association between fasting and increased AC.23,31,32 The increase in AC was greater in the non-fasting groups in Moradia et al.31 and Sakar et al.32
3.10 Preterm Birth
According to Tith et al.,33 the risk of preterm birth is significantly increased when participants fasted during second-trimester. Arabic-speaking women who fasted between weeks 15 and 21 of gestation and weeks 22 and 27 had 1.33 (95% CI:1.06-1.68) and 1.53 (95% CI:1.21-1.93) times the risk of very preterm birth, respectively than non-fasting group. When both parents had Arabic mother tongue and spoke the language at home, RF in weeks 15 to 21 was linked to 1.38 times the risk of very preterm birth (95% CI:1.03-1.85) and 1.65 times in weeks 22 to 27 (95% CI:1.23-2.21). If compared to non-Arabic speakers who were pregnant in the same period, the risk reduced to 1.25 (95% CI:1.02-1.53) and 1.33 (95% CI:1.08-1.63) times respectively.
Petherick et al.24 and Hossain et al.28 showed no association between RF and the risk of preterm birth, even after adjusting for covariables. Awwad and colleagues21 noted that despite having higher incidence of preterm birth in the fasting group, the difference was insignificant.
3.11 Biophysical Profile (BPP)
All study results showed no significant difference between fasting pregnant women and non-fasting pregnant women.26,29,30In one study,29,30 there was an average score of 7.8 in the fasting group, compared to 7.0 in the control group. However, the difference was statistically insignificant.

3.12 APGAR Score

Hossain and colleague’s study28 demonstrated that 5-min APGAR score was significantly higher in the fasting group than non-fasting group (9.00±0.01 vs 8.92±0.53, p=0.044). While the study showed a similar trend for 1-min Apgar score, the difference was not significant. In Abd-Allah Rezk et al.’s study26, the 5-min APGAR score for non-fasting group had an average of 8.52±1.1, while the fasting group had an average of 8.44±1.2. Similarly, in Karatake et al. ’s study,25 there was insignificant difference between the two groups for both 1-min and 5-min APGAR scores.
3.13 Stillbirth
In both adjusted and unadjusted models, RF during first and second trimesters was not associated with risk of early and late stillbirths when compared to no exposure. Nevertheless, when the data was further classified according to causes of death, Bernier and colleagues34 found that Ramadan exposure between weeks 15 to 21 of pregnancy increased the risk of early stillbirth due to congenital anomaly by 3.96 times (95% CI1.35-11.57). However, this reported findings has not been adjusted for covariates.
3.14 Other outcomes
Seckin et al.23 reported that a significantly higher number of participants with normal initial AFI subsequently developed oligohydramnios (20/82 vs 6/87,P=0.03) in the fasting group. Naderi et al.17 reported insignificant difference in the rate of fundal height increment between fasting and non-fasting groups. In Alwasel et al.’s study,19 there was no significant association between fasting and chest circumference regardless of baby’s gender and fasting trimester. In Abd-Allah Rezk et al.’s study,26 the difference in reactivity of the non-stress test between fasting and non-fasting groups was insignificant.
Discussion
4.1 Main Findings
Our study demonstrated few significant findings. RF negatively affected neonatal weight,21 AFI,23,25gestational age at delivery,19 preterm birth33 and changes in growth parameters except abdominal circumference.19,32
We found three other reviews11,35,36 that looked into the effects of RF during pregnancy on perinatal outcomes. Glazier and colleagues11 had reported similar outcomes, specifically preterm birth and birth weight. They found that RF did not significantly affect the frequency of preterm delivery (OR 0.99,95% CI 0.72-1.37), birth weight (SMD 0.03, 95% CI 0.00-0.05) and proportion of low-birth-weight babies (OR 1.05,95% CI 0.87-1.26), irrespective of pregnancy trimesters. Oosterwijk et al.35 and Noshili et al.36 included data on fetal growth indices and birth indices. Both reviews inferred that RF has some associations with fetal growth indices and birth indices but predominantly found in lower quality studies. Certain included articles23,25,32described lower AFI in the fasting group during second or third trimester of pregnancy, and BPD, HC and FL32 were significantly affected by fasting (p<0.05). Only one high quality study mentioned that mean birth weight was significantly lower in exposed neonates (108g, p=0.024). Apart from that, differences in birth indices were statistically insignificant.
4.2 Interpretation
Our findings are consistent with data gathered by the three systematic reviews,11,35,36 with little supporting evidence that RF has some associations with poor fetal health. This is because we discovered that evidence linking RF and changes in certain fetal outcomes only appeared in one of many articles examining them. Notably, there is a trend that all significant changes occurred especially when pregnant women fasted during second or third trimesters. This could be an important reference point for future studies whereby fasting during second and third trimesters of pregnancy may result in higher risks of poor fetal outcomes.
4.3 Strengths and Limitations
Maternal ethnicity and height were not adjusted for in all the articles. Certain ethnicities are known to have above average height and maternal height is a strong predictor of offspring nutritional status. Stulp and colleagues37 mentioned that taller parents have heavier newborns. Birth weight was found to be both independently and positively affected by maternal and paternal height, with a 66% stronger effect ascribed to maternal influence. Inversely, a research done in Brazil38 showed that adult stature reflects nutritional status and health processes throughout life. Earlier research demonstrated that short stature is likely due to combined genetic and environmental effects, such as nutritional stresses in early stages of life.39 Short mothers with poorer quality of life are likely to provide insufficient nutrients to fetuses during pregnancy, resulting in small-for-gestational-age (SGA) babies.39 Similarly, mothers who were SGA at birth are at greater risks of giving birth to SGA offspring.39
Our original intent of this study was to investigate the effects of RF on fetal movements because it is one of the easiest ways to monitor fetal growth and activity. Decreased fetal movement may be the first sign of an underlying pathology and warrants further assessment. We had to modify the primary objective of this study because there was not enough data for further analysis. We only found two out of eighteen included articles that reported fetal movement as an outcome of measurement in the form of non-stress tests.
Another limitation identified is that most studies are performed in the Middle East, and less so in Western and Asian countries. Dietary patterns and cultures differ across countries. It may be a confounding factor that has not been accounted for during this study. For instance, Middle Easterners usually consume healthy Mediterranean diet which mainly consists of whole foods including vegetables, fruits, whole wheat, legumes, nuts, seafood and spices. Red meat, dairy and processed food are typically in smaller amounts than a standard Western diet. Depending on the types of food pregnant mothers eat while breaking fast during Ramadan, there will be a difference in nutritional components, which inadvertently affects fetal growth parameters. For this systematic review, we could not find any article that was based in the Asian community, therefore it is difficult to translate any evidence into practical recommendations that are aimed towards Asian lifestyle.
Furthermore, only articles published in the English language and involved human studies are included. There could be articles not published in the English language related to our topic but are omitted. Some articles demonstrated potential health effects of fasting through animal models. Therefore, they were not included in this study. For example, Alkhalefah et al.40 reported intermittent fasting in pregnant Wistar rats induces fetal growth restriction and down-regulated placental amino acid transport. For these reasons, the number of articles included in our review was narrowed down, which could contribute to lower strength of evidence.
Although some individual studies have associated RF with potential health impacts, we could not perform a meta-analysis to calculate an overall effect due to limitations of data available. While some outcomes could not be presented as mean and standard deviation, most are not available from included studies. Correspondingly, we could not determine the effect size and heterogeneity of each outcome.
There are two studies36,41 referenced in this review that looked at long-term consequences of individuals exposed to RF in utero, including physical traits and cognitive effects. As our study mainly focuses on short-term or immediate outcomes, those data are excluded, but they could always be considered for future research questions.
Conclusion
This systematic review found that there is insufficient data to associate RF with poor fetal outcomes.
5.1 Implications for Research
While there are negative associations between RF and fetal health, the findings appeared to be inconsistent across studies. Our review highlighted the importance of having further prospective research and outcome-specific retrospective observational studies that take into account multiple confounding factors to provide a more definitive evidence. We are hoping that this systematic review could be used as a guide for future pilot studies across different regions to look at the effects of RF on fetal health, to provide reassurance and advice to pregnant mothers who wish to safely practise fasting and avoid any adverse outcomes.
5.2 Implications for Practice
This systematic review provides recommendation to health professionals and pregnant women on the safety of RF during pregnancy.
Acknowledgement
None.
Author Contribution
The study was formulated by AKWO, ALY and AJHF. AR carried out the literature search. ALY and AJHF screened through and selected eligible studies. Differences in opinion were sorted out by AKWO. AKWO and ALY extracted data and carried out the data analysis. AKWO and AJHF performed quality assessment for all included studies. VJTA supervised the data analysis and write-up of study. All authors were involved in interpretation of data and revised the article critically.
Conflict of Interests
None declared.
Ethical Approval
None.
References:
  1. Finnell JS, Saul BC, Goldhamer AC, Myers TR. Is fasting safe? A chart review of adverse events during medically supervised, water-only fasting. BMC Complement Altern Med. 2018 Feb 20;18(1):67. doi: 10.1186/s12906-018-2136-6.
  2. Templeman, I., Gonzalez, J., Thompson, D., & Betts, J. (2020). The role of intermittent fasting and meal timing in weight management and metabolic health. Proceedings of the Nutrition Society, 79(1), 76-87. doi:10.1017/S0029665119000636.
  3. Britannica, T. Editors of Encyclopaedia. ”Ramadan.” Encyclopedia Britannica, September 10, 2020. https://www.britannica.com/topic/Ramadan. Accessed 27 January 2021.
  4. Leiper, J., Molla, A. & Molla, A. Effects on health of fluid restriction during fasting in Ramadan. Eur J Clin Nutr 57, S30–S38 (2003). https://doi.org/10.1038/sj.ejcn.1601899.
  5. Lessan N, Ali T. Energy Metabolism and Intermittent Fasting: The Ramadan Perspective. Nutrients. 2019 May 27;11(5):1192. doi: 10.3390/nu11051192.
  6. Ziaee V, Kihanidoost Z, Younesian M, Akhavirad MB, Bateni F, Kazemianfar Z, Hantoushzadeh S. The effect of ramadan fasting on outcome of pregnancy. Iran J Pediatr. 2010 Jun;20(2):181-6. PMID: 23056701; PMCID: PMC3446023.
  7. Frøen JF, Heazell AE, Tveit JV, Saastad E, Fretts RC, Flenady V. Fetal movement assessment. Semin Perinatol. 2008 Aug;32(4):243-6. doi: 10.1053/j.semperi.2008.04.004.
  8. Singh G, Sidhu K. Daily Fetal Movement Count Chart : Reducing Perinatal Mortality in Low Risk Pregnancy. Med J Armed Forces India. 2008 Jul;64(3):212-3. doi: 10.1016/S0377-1237(08)80094-9.
  9. Warrander LK, Batra G, Bernatavicius G, Greenwood SL, Dutton P, Jones RL, Sibley CP, Heazell AE. Maternal perception of reduced fetal movements is associated with altered placental structure and function. PLoS One. 2012;7(4):e34851. doi: 10.1371/journal.pone.0034851.
  10. Parveen R, Khakwani M, Latif M, Tareen AU. Maternal and Perinatal outcome after Ramadan Fasting. Pak J Med Sci. 2020 Jul-Aug;36(5):894-898. doi: 10.12669/pjms.36.5.2612. PMID: 32704259; PMCID: PMC7372656.
  11. Glazier JD, Hayes DJL, Hussain S, D’Souza SW, Whitcombe J, Heazell AEP, Ashton N. The effect of Ramadan fasting during pregnancy on perinatal outcomes: a systematic review and meta-analysis. BMC Pregnancy Childbirth. 2018 Oct 25;18(1):421. doi: 10.1186/s12884-018-2048-y. PMID: 30359228; PMCID: PMC6202808.
  12. Page M J, McKenzie J E, Bossuyt P M, Boutron I, Hoffmann T C, Mulrow C D et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews BMJ 2021; 372 :n71 doi:10.1136/bmj.n71
  13. Veritas Health Innovation. Covidence Systematic Review Software. Melbourne, Australia. Available online: www.covidence.org.
  14. Erol A, Baylan G, Yazici F. Do Ramadan fasting restrictions alter eating behaviours? Eur Eat Disord Rev. 2008;16(4):297–301.
  15. Bryant J, Jamil RT, Thistle J. Fetal Movement. [Updated 2020 Nov 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470566/.
  16. Wells G, Shea B, O’Connell D, Peterson J, Welch V, Losos M, Tugwell P: The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses. 2013, http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp.
  17. Naderi T, Kamyabi Z. Determination of fundal height increase in fasting and non-fasting pregnant women during Ramadan. Saudi Med J. 2004 Jun;25(6):809-10. PMID: 15195219.
  18. Alwasel SH, Abotalib Z, Aljarallah JS, Osmond C, Alkharaz SM, Alhazza IM, Badr G, Barker DJ. Changes in placental size during Ramadan. Placenta. 2010 Jul;31(7):607-10. doi: 10.1016/j.placenta.2010.04.010. Epub 2010 Jun 2. PMID: 20621763.
  19. Alwasel SH, Abotalib Z, Aljarallah JS, Osmond C, Alkharaz SM, Alhazza IM, Harrath A, Thornburg K, Barker DJ. Sex differences in birth size and intergenerational effects of intrauterine exposure to Ramadan in Saudi Arabia. Am J Hum Biol. 2011 Sep-Oct;23(5):651-4. doi: 10.1002/ajhb.21193. Epub 2011 May 31. PMID: 21630372.
  20. Ozturk E, Balat O, Ugur MG, Yazıcıoglu C, Pence S, Erel Ö, Kul S. Effect of Ramadan fasting on maternal oxidative stress during the second trimester: a preliminary study. J Obstet Gynaecol Res. 2011 Jul;37(7):729-33. doi: 10.1111/j.1447-0756.2010.01419.x. Epub 2011 Mar 9. PMID: 21736666.
  21. Awwad J, Usta IM, Succar J, Musallam KM, Ghazeeri G, Nassar AH. The effect of maternal fasting during Ramadan on preterm delivery: a prospective cohort study. BJOG. 2012 Oct;119(11):1379-86. doi: 10.1111/j.1471-0528.2012.03438.x. Epub 2012 Jul 25. PMID: 22827751.
  22. Savitri AI, Yadegari N, Bakker J, van Ewijk RJ, Grobbee DE, Painter RC, Uiterwaal CS, Roseboom TJ. Ramadan fasting and newborn’s birth weight in pregnant Muslim women in The Netherlands. Br J Nutr. 2014 Nov 14;112(9):1503-9. doi: 10.1017/S0007114514002219. Epub 2014 Sep 18. PMID: 25231606.
  23. Seckin KD, Yeral MI, Karslı MF, Gultekin IB. Effect of maternal fasting for religious beliefs on fetal sonographic findings and neonatal outcomes. Int J Gynaecol Obstet. 2014 Aug;126(2):123-5. doi: 10.1016/j.ijgo.2014.02.018. Epub 2014 Apr 18. PMID: 24792406.
  24. Petherick ES, Tuffnell D & Wright J. Experiences and outcomes of maternal Ramadan fasting during pregnancy: results from a sub-cohort of the Born in Bradford birth cohort study. BMC Pregnancy Childbirth. 2014 Sep 26;14:335.https://doi.org/10.1186/1471-2393-14-335.
  25. Karateke A, Kaplanoglu M, Avci F, Kurt RK, Baloglu A. The effect of Ramadan fasting on fetal development. Pak J Med Sci. 2015 Nov-Dec;31(6):1295-9. doi: 10.12669/pjms.316.8562. PMID: 26870085; PMCID: PMC4744270.
  26. Abd-Allah Rezk M, Sayyed T, Abo-Elnasr M, Shawky M, Badr H. Impact of maternal fasting on fetal well-being parameters and fetal-neonatal outcome: a case-control study. J Matern Fetal Neonatal Med. 2016 Sep;29(17):2834-8. doi: 10.3109/14767058.2015.1105955. Epub 2015 Nov 2. PMID: 26453375.
  27. Sakar MN, Balsak D, Verit FF, Zebitay AG, Buyuk A, Akay E, Turfan M, Demir S, Yayla M. The effect of Ramadan fasting and maternal hypoalbuminaemia on neonatal anthropometric parameters and placental weight. J Obstet Gynaecol. 2016 May;36(4):483-6. doi: 10.3109/01443615.2015.1086989. Epub 2015 Oct 14. PMID: 26467047.
  28. Hossain N, Samuel M, Mughal S, Shafique K. Ramadan Fasting: Perception and maternal outcomes during Pregnancy. Pak J Med Sci. 2021;37(5):1262-1267. doi:https://doi.org/10.12669/pjms.37.5.4109
  29. Dikensoy E, Balat O, Cebesoy B, Ozkur A, Cicek H, Can G. Effect of fasting during Ramadan on fetal development and maternal health. J Obstet Gynaecol Res. 2008 Aug;34(4):494-8. doi: 10.1111/j.1447-0756.2008.00814.x. PMID: 18937702.
  30. Dikensoy E, Balat O, Cebesoy B, Ozkur A, Cicek H, Can G. The effect of Ramadan fasting on maternal serum lipids, cortisol levels and fetal development. Arch Gynecol Obstet. 2009 Feb;279(2):119-23. doi: 10.1007/s00404-008-0680-x. Epub 2008 May 17. PMID: 18488237.
  31. Moradia M. The effect of Ramadan fasting on fetal growth and Doppler indices of pregnancy. Journal of research in medical sciences : the official journal of Isfahan University of Medical Sciences. 2011;16:165-9.
  32. Sakar MN, Gultekin H, Demir B, Bakir VL, Balsak D, Vuruskan E, Acar H, Yucel O, Yayla M. Ramadan fasting and pregnancy: implications for fetal development in summer season. J Perinat Med. 2015 May;43(3):319-23. doi: 10.1515/jpm-2013-0289. PMID: 24810552.
  33. Tith RM, Bilodeau-Bertrand M, Lee GE, Healy-Profitós J, Auger N. Fasting during Ramadan Increases Risk of Very Preterm Birth among Arabic-Speaking Women. J Nutr. 2019 Oct 1;149(10):1826-1832. doi: 10.1093/jn/nxz126. PMID: 31198942.
  34. Bernier J, Bilodeau-Bertrand M, Djeha A, Auger N. Ramadan exposure during early pregnancy and risk of stillbirth in Arab women living in Canada. Paediatr Perinat Epidemiol. 2021 Nov;35(6):689-693. doi: 10.1111/ppe.12761. Epub 2021 May 26. PMID: 34080705.
  35. Oosterwijk VN, Molenaar JM, van Bilsen LA, Kiefte-de Jong JC. Ramadan Fasting during Pregnancy and Health Outcomes in Offspring: A Systematic Review. Nutrients. 2021 Oct;13(10):3450.
  36. Noshili AI, Jamshed M, Hamdi AM, Noshaily AJ, Zammar AMA, Jabbari MYA, Khudhayr SY, Alshakarah NF, Almutairi SM, Sale AJ. Effects of Fasting in Ramadan on Pregnancy Outcome: Systematic Review. International Journal of Clinical Skills. 2022 May 30;16(4).242. DOI: 10.37532/1753-0431
  37. Stulp G, Verhulst S, Pollet TV, Nettle D, Buunk AP. Parental height differences predict the need for an emergency caesarean section.PLoS One. 2011;6(6):e20497. doi:10.1371/journal.pone.0020497
  38. Britto RPdA, Florêncio TMT, Benedito Silva AA, Sesso R, Cavalcante JC, Sawaya AL. Influence of Maternal Height and Weight on Low Birth Weight: A Cross-Sectional Study in Poor Communities of Northeastern Brazil . PLOS ONE 2013 Nov 11;8(11): e80159. https://doi.org/10.1371/journal.pone.0080159
  39. Khatun W, Rasheed S, Alam A, Huda TM, Dibley MJ. Assessing the Intergenerational Linkage between Short Maternal Stature and Under-Five Stunting and Wasting in Bangladesh. Nutrients. 2019;11(8):1818. Published 2019 Aug 7. doi:10.3390/nu11081818
  40. Alkhalefah A, Dunn WB, Allwood JW, Parry KL, Houghton FD, Ashton N, Glazier JD. Maternal intermittent fasting during pregnancy induces fetal growth restriction and down-regulated placental system A amino acid transport in the rat. Clinical Science. 2021 Jun 11;135(11):1445-66.
  41. Mahanani MR, Abderbwih E, Wendt AS, Deckert A, Antia K, Horstick O, Dambach P, Kohler S, Winkler V. Long-Term Outcomes of in Utero Ramadan Exposure: A Systematic Literature Review. Nutrients. 2021 Dec 17;13(12):4511. doi: 10.3390/nu13124511. PMID: 34960063; PMCID: PMC8704584.
Table S1: Search strategies
OVID Medline