Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2024 Jan;103(1):85-92.
doi: 10.1111/aogs.14700. Epub 2023 Oct 30.

Placental size at gestational week 36: Comparisons between ongoing pregnancies and deliveries

Helene Fjeldvik Peterson  1   2 , Anne Eskild  1   2 , Silje Sommerfelt  1 , Vigdis Hillestad  1   2   3
Affiliations

Placental size at gestational week 36: Comparisons between ongoing pregnancies and deliveries

Helene Fjeldvik Peterson et al. Acta Obstet Gynecol Scand. 2024 Jan.

Abstract

Introduction: We aimed to compare placental size and placental size relative to fetal size (ratio) in ongoing pregnancies examined by magnetic resonance imaging (MRI) at gestational week 36 with placental size among all deliveries at gestational week 36 during the same time period.

Material and methods: Ongoing unselected singleton pregnancies (n = 89) were examined by MRI at median gestational week 36+5 days during 2017-2018, and placental and fetal volumes (cm3 ) were calculated. The placental size and ratio in ongoing pregnancies were compared with placental size and ratio among all deliveries in Norway at gestational week 36 (median gestational week 36+4 days) during 2016-2019 (n = 5582). For comparison of size, we converted volume (cm3 ) in ongoing pregnancies into grams as: cm3 × 1.05 (density of placental and fetal tissue).

Results: In ongoing pregnancies, median placental size was 873 (interquartile range [IQR] 265) grams and median size of all delivered placentas was 613 (IQR 290) grams. Placental size was smaller among the delivered placentas independent of delivery mode: 760 (IQR 387) grams among elective cesarean deliveries (n = 465) and 590 (IQR 189) grams among vaginal deliveries after spontaneous onset of labor (n = 2478). Median ratio in ongoing pregnancies was higher than among deliveries: 0.31 (IQR 0.08) vs 0.21 (IQR 0.08). The ratio was higher in ongoing pregnancies independent of delivery mode: 0.24 (IQR 0.17) among elective cesarean deliveries vs 0.21 (IQR 0.05) among vaginal deliveries after spontaneous onset of labor.

Conclusions: The placenta is larger in ongoing pregnancies than among deliveries. This finding suggests that placental size decreases during labor and delivery, possibly by transfer of blood to the fetus. Our finding also suggests that reference values of placental size based on delivered placentas are not valid for ongoing pregnancies.

Keywords: birth; obstetrics; placenta; pregnancy.

PubMed Disclaimer

Conflict of interest statement

The authors have stated explicitly that there are no conflicts of interest in connection with this article.

Figures

FIGURE 1
FIGURE 1
(A) Distribution of placental size (g) in ongoing pregnancies estimated by magnetic resonance imaging (MRI) and (B) distribution of placental size (g) among deliveries at gestational week 36. (C) Distribution of placental size (g)/fetal size (g) in ongoing pregnancies estimated by MRI. (D) Distribution of placental size (g)/newborn size (g) among deliveries, at gestational week 36.
FIGURE 2
FIGURE 2
(A) Placental size at gestational week 36 in ongoing pregnancies estimated by magnetic resonance imaging (MRI) (g), among elective cesarean deliveries (g), acute cesarean delivery after spontaneous onset of labor (acute cesarean delivery [g]) and among women with a vaginal delivery after spontaneous onset of labor (vaginal delivery [g]). (B) Placental size/fetal or newborn size at gestational week 36 in ongoing pregnancies estimated by MRI, among elective cesarean deliveries, acute cesarean delivery and among women with a vaginal delivery. Boxes represents median values, with 1st and 3rd quartiles. Whiskers represent the minimum and maximum values, excluding outliers. Outliers marked by an asterix (*).
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

References

    1. Thompson JM, Irgens LM, Skjaerven R, Rasmussen S. Placenta weight percentile curves for singleton deliveries. BJOG. 2007;114:715‐720. - PubMed
    1. Almog B, Shehata F, Aljabri S, Levin I, Shalom‐Paz E, Shrim A. Placenta weight percentile curves for singleton and twins deliveries. Placenta. 2011;32:58‐62. - PubMed
    1. Dombrowski MP, Berry SM, Johnson MP, Saleh AA, Sokol RJ. Birth weight‐length ratios, ponderal indexes, placental weights, and birth weight‐placenta ratios in a large population. Arch Pediatr Adolesc Med. 1994;148:508‐512. - PubMed
    1. Wallace JM, Bhattacharya S, Horgan GW. Gestational age, gender and parity specific centile charts for placental weight for singleton deliveries in Aberdeen, UK. Placenta. 2013;34:269‐274. - PubMed
    1. Burkhardt T, Schäffer L, Schneider C, Zimmermann R, Kurmanavicius J. Reference values for the weight of freshly delivered term placentas and for placental weight‐birth weight ratios. Eur J Obstet Gynecol Reprod Biol. 2006;128:248‐252. - PubMed