Placental weight and birth weight to placental weight ratio in monochorionic and dichorionic growth-restricted and non-growth-restricted twins

Souza, Mariângela Alves; de Lourdes Brizot, Maria; Biancolin, Sckarlet Ernandes; Schultz, Regina; de Carvalho, Mário Henrique Burlacchini; Francisco, Rossana Pulcineli Vieira; Zugaib, Marcelo

doi:10.6061/clinics/2017(05)02

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CLINICAL SCIENCE • Clinics 72 (5) • May 2017 • https://doi.org/10.6061/clinics/2017(05)02 copy

Placental weight and birth weight to placental weight ratio in monochorionic and dichorionic growth-restricted and non-growth-restricted twins

Authorship SCIMAGO INSTITUTIONS RANKINGS

OBJECTIVE:

The aim of the present study was to compare the placental weight and birth weight/placental weight ratio for intrauterine growth-restricted and non-intrauterine growth-restricted monochorionic and dichorionic twins.

METHODS:

This was a retrospective analysis of placentas from twin pregnancies. Placental weight and the birth weight/placental weight ratio were compared in intrauterine growth-restricted and non-intrauterine growth-restricted monochorionic and dichorionic twins. The association between cord insertion type and placental lesions in intrauterine growth-restricted and non-intrauterine growth-restricted monochorionic and dichorionic twins was also investigated.

RESULTS:

A total of 105 monochorionic (intrauterine growth restriction=40; non-intrauterine growth restriction=65) and 219 dichorionic (intrauterine growth restriction=57; non-intrauterine growth restriction=162) placentas were analyzed. A significantly lower placental weight was observed in intrauterine growth-restricted monochorionic (p=0.022) and dichorionic (p<0.001) twins compared to non-intrauterine growth-restricted twins. There was no difference in the birth weight/placental weight ratio between the intrauterine growth restriction and non-intrauterine growth restriction groups for either monochorionic (p=0.36) or dichorionic (p=0.68) twins. Placental weight and the birth weight/placental weight ratio were not associated with cord insertion type or with placental lesions.

CONCLUSION:

Low placental weight, and consequently reduced functional mass, appears to be involved in fetal growth restriction in monochorionic and dichorionic twins. The mechanism by which low placental weight influences the birth weight/placental weight ratio in intrauterine growth-restricted monochorionic and dichorionic twins needs to be determined in larger prospective studies.

Twin Pregnancy; Placental Pathology; Placental Weight; Birth Weight/Placental Weight Ratio; Monochorionic Twin; Growth Restriction

	Monochorionic n=105	Dichorionic n=219	p
Maternal characteristics
Age (yr), mean ± SD	26.9 (6.68)	29.58 (6.45)	0.01^* * Student’s t test;
Stature (m), mean ± SD	1.60 (0.06)	1.61 (0.06)	0.37^* * Student’s t test;
White ethnicity, n (%)	61 (58.1)	115 (52.5)	0.40^# # Chi-square test;
Multiparous, n (%)	19 (18.1)	72 (32.9)	0.006^# # Chi-square test;
Smoking during pregnancy, n (%)	11 (10.5)	41 (18.7)	0.05^# # Chi-square test;
Alcohol abuse during pregnancy, n (%)	0 (0)	5 (2.3)	0.18^§ § Fisher’s exact test
Illicit substance use during pregnancy, n (%)	1 (1)	8 (3.7)	0.28^§ § Fisher’s exact test
Medical disorders prior to pregnancy, n (%)^ Medical disorders prior to pregnancy: chronic hypertension, diabetes, asthma, cardiopathy, hypothyroidism, thrombophilia, or chronic kidney disease.	28 (26.7)	47 (21.6)	0.33^# # Chi-square test;
Gestational complications	20 (19)	59 (26.9)	0.13^# # Chi-square test;
Perinatal characteristics
Twin growth restriction, n (%)	40 (38.1)	57 (26)	0.04^# # Chi-square test;
Birth weight discordance (%), mean ± SD	15.63 (13.51)	12.3 (11.05)	0.03^* * Student’s t test;
Gestational age at delivery, mean ± SD	34.45 (2.55)	35.55 (2.89)	0.001^* * Student’s t test;
Total birth weight (g), mean ± SD	3913.98 (919.17)	4537.36 (1106.89)	<0.001^* * Student’s t test;
Placental characteristics
Total placental weight (g), mean ± SD	645.94 (133.02)	730.33 (186.39)	<0.001^* * Student’s t test;
Birth weight/placental weight ratio	6.12 (1.16)	6.32 (1.18)	0.17
Number of lesions, mean ± SD	0.60 (0.83)	0.57 (0.75)	0.79^* * Student’s t test;

	Median total birth weight in grams (range)				Median total placental weight in grams (range) (number of cases)
GA at Birth (wks)	Monochorionic, N=105		Dichorionic, N=219		Monochorionic, N=105			Dichorionic, N=219
GA at Birth (wks)	IUGR (n=40)	nIUGR (n=65)	IUGR (n=57)	nIUGR (n=162)	IUGR (n=40)	nIUGR (n=65)	p	IUGR (n=57)	nIUGR (n=162)	p
≤28	-	1965 (1850-3053)	-	1620 (1280-2440)	(0)	415 (330-575) (6)	-	(0)	395 (185-617) (8)	-
29-31	2390 (2220-2560)	2936 (2370-3394)	2040 (1770-2360)	2810 (2370-3600)	530 (520-540) (2)	529 (465-730) (7)	0.99^* * Mann-Whitney U test;	335 (230-500) (3)	542 (365-710) (14)	0.03^* * Mann-Whitney U test;
32-34	3185 (1970-3920)	3845 (2950-4820)	3320 (2640-4120)	3980 (3090-5280)	494.35 (340-690) (16)	650 (540-820) (16)	<0.001^* * Mann-Whitney U test;	603 (420-960) (13)	684 (475-1035) (22)	0.20^* * Mann-Whitney U test;
≥35	3990 (3010-4670)	4819 (3840-5950)	4350 (3260-5200)	5280 (3880-6570)	692.5 (505-830) (22)	696 (450-990) (36)	0.25^* * Mann-Whitney U test;	645 (450-1130) (41)	807.5 (505-1340) (118)	<0.001^* * Mann-Whitney U test;
All (24-38)	3650 (1970-4670)	4400 (1850-5950)	4180 (1770-5200)	5035 (1280-6570)	627.5 (340-830) (40)	665 (330-990) (65)	0.02^ Student’s t test.	620 (230-1130) (57)	765 (185-1340) (162)	<0.001^ Student’s t test.

BW/PW, median (range) (number of cases)
GA at Birth (weeks)	Monochorionic, N=105		p	Dichorionic, N=219		p
GA at Birth (weeks)	IUGR (n=40)	nIUGR (n=65)	p	IUGR (n=57)	nIUGR (n=162)	p
≤28	(0)	5.12 (3.28-7.53) (6)	-	(0)	4.11 (3.51-6.91) (8)	-
29-31	4.50 (4.26-4.74) (2)	5.55 (3.20-6.40) (7)	0.33^* * Mann-Whitney U test;	5.28 (4.72-8.86) (3)	5.01 (4.12-7.12) (14)	0.51^* * Mann-Whitney U test;
32-34	6.21 (3.53-8.76) (16)	5.85 (4.60-7.04) (16)	0.32^* * Mann-Whitney U test;	5.28 (3.73-7.92) (13)	6.08 (4.16-9.22) (22)	0.18^* * Mann-Whitney U test;
≥35	5.92 (4.12-8.02) (22)	6.83 (5.12-9.93) (36)	0.006^* * Mann-Whitney U test;	6.59 (4.60-9.29) (41)	6.49 (3.99-9.23) (118)	0.67^* * Mann-Whitney U test;
All (24-38)	5.93 (3.53-8.76) (40)	6.20 (3.24-9.93) (65)	0.36^ Student’s t test.	6.38 (3.73-9.29) (57)	6.32 (3.51-9.23) (162)	0.68^ Student’s t test.
One twin with IUGR (24-38)	5.94 (3.53- 8.77) (33)	6.20 (3.24-9.93) (65)	0.454^* * Mann-Whitney U test;	6.38 (3.74-9.30) (52)	6.32 (3.51-9.23) (162)	0.662^* * Mann-Whitney U test;
Both twins with IUGR (24-38)	5.27 (4.28- 7.36) (7)	6.20 (3.24-9.93) (65)	0.242^* * Mann-Whitney U test;	5.77 (5.25- 7.13) (5)	6.32 (3.51-9.23) (162)	0.659^* * Mann-Whitney U test;

	Monochorionic						Dichorionic
	IUGR		p ^* * Mann-Whitney U test.	nIUGR		p ^* * Mann-Whitney U test.	IUGR		p ^* * Mann-Whitney U test.	nIUGR		p ^* * Mann-Whitney U test.
	Paracentral N=3	Peripheral N=33	p ^* * Mann-Whitney U test.	Paracentral N=17	Peripheral N=41	p ^* * Mann-Whitney U test.	Paracentral N=34	Peripheral N=18	p ^* * Mann-Whitney U test.	Paracentral N=80	Peripheral N=57	p ^* * Mann-Whitney U test.
Placental weight	680 (530-730)	630 (390-830)	0.66	650 (417-990)	675 (330-950)	0.80	684 (230-1130)	582.5 (335-895)	0.02	747.5 (365-1340)	780 (185-1095)	0.71
BW/PW ratio	5.89 (4.12-6.73)	5.94 (3.53-8.76)	0.66	5.80 (4.60-8.11)	6.09 (3.24-9.93)	0.58	6.43 (4.38-8.96	6.06 (4.14-9.29)	0.55	6.39 (3.79-9.23)	6.26 (3.51-9.22)	0.53

Placental Lesions	Total N (%)	Chorionicity		p	Monochorionic		Dichorionic			p
Placental Lesions	Total N (%)	MC N=105	DC N=219	p	IUGR N=40	nIUGR n=65	p	IUGR N=57	nIUGR n=162	p
At least one lesion	113 (34.9)	41 (39)	72 (32.9)	0.32^* * Chi-square test;	20 (50)	21 (32.3)	0.09^* * Chi-square test;	21 (36.8)	51 (31.5)	0.51^* * Chi-square test;
Chorangiosis	34 (10.5)	17 (16.2)	17 (7.8)	0.03^* * Chi-square test;	8 (20)	9 (13.8)	0.42^* * Chi-square test;	2 (3.5)	15 (9.3)^* * Chi-square test;	0.25^# # Fisher’s exact test.
Fibrin deposition	16 (4.9)	3 (2.9)	13 (5.9)	0.28^# # Fisher’s exact test.	2 (5)	1 (1.5)	0.55^# # Fisher’s exact test.	2 (3.5)	11 (6.8)	0.52^# # Fisher’s exact test.
Intraplacental hematoma	35 (10.8)	10 (9.5)	25 (11.4)	0.70^* * Chi-square test;	4 (10)	6 (9.2)	0.99^# # Fisher’s exact test.	11 (19.3)	14 (8.6)	0.05^* * Chi-square test;
Villous immaturity	13 (4)	7 (6.7)	6 (2.7)	0.12^# # Fisher’s exact test.	4 (10)	3 (4.6)	0.42^# # Fisher’s exact test.	1 (1.8)	5 (3.1)	0.99^# # Fisher’s exact test.
Villous infarction	40 (12.3)	13 (12.4)	27 (12.3)	0.99^* * Chi-square test;	4 (10)	9 (13.8)	0.76^# # Fisher’s exact test.	11 (19.3)	16 (9.9)	0.09^* * Chi-square test;
Chronic villitis	7 (2.2)	3 (2.9)	4 (1.8)	0.68^# # Fisher’s exact test.	3 (7.5)	0 (0)	0.05^# # Fisher’s exact test.	0 (0)	4 (2.5)	0.57^# # Fisher’s exact test.

Groups	No placental lesions Mean (±SD)	At least one lesion Mean (±SD)	p ^* * Student’s t test.
All placentas, n=324	708.99 (182.87)	691.75 (160.26)	0.39
Monochorionic
All, n=105	647.88 (136.91)	642.91 (128.32)	0.85
IUGR, n=40	607.19 (137.80)	609.55 (117.17)	0.95
nIUGR, n=65	666.38 (133.99)	674.68 (133.12)	0.81
Dichorionic
All, n=219	735.60 (194.06)	719.56 (170.46)	0.55
IUGR, n=57	662.16 (155.12)	612.79 (158.55)	0.25
nIUGR, n=162	759.42 (199.98)	763.52 (156.36)	0.89

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[1] Corresponding author. E-mail: mlbrizot@uol.com.br