Hypertensive disorders of pregnancy after multifetal pregnancy reduction: a systematic review and meta-analysis

Figures & data

Table 1. Definitions.

Primary outcome	Definition
Gestational hypertension	Persistent de novo hypertension that develops at or after 20 weeks of gestation in the absence of features of preeclampsia (30)
Preeclampsia	Gestational hypertension accompanied by one or more of the following new-onset conditions at or after 20 weeks of gestation: 1) proteinuria, 2) other maternal organ dysfunction (acute kidney injury, liver involvement, neurological complications, severe headaches, persistent visual scotomata, or hematological complications), and 3) uteroplacental dysfunction (30)
Secondary outcome
Gestational diabetes	Any degree of glucose intolerance with onset or first recognition during pregnancy (31)
Anemia in pregnancy	Hemoglobin concentration of less than 11.0 g/dL (32)
Postpartum hemorrhage	Cumulative blood loss of ≥1000 ml within 24 h after childbirth (33)
Placental abruption	Early separation of placenta from the lining of the uterus before completion of the second stage of labor (34)
Uterine rupture	A complete division of all three layers of the uterus (35)
HELLP syndrome	A serious complication in pregnancy characterized by hemolysis, elevated liver enzymes, and low platelet count (36)
Eclampsia	New onset of generalized tonic-clonic seizures in a woman with preeclampsia (37)
Amniotic fluid embolism	Life-threatening obstetric emergency characterized by sudden cardiorespiratory collapse and disseminated intravascular coagulation (38)

Figure 1. Flowchart depicting article screening and inclusion.

Table 2. Baseline characteristics of the included studies.

Study details					Sample size (total); n				Reduction			Primary outcome
					MFPR		Ongoing pregnancy
First author	Country	Year	Design	Study period	3 → 2	≥3 → 2	Twin	Triplet	Approach	Method	GA; weeks	HDP	Definition
Alexander (41)	US	1995	RCS	1988–1993	-	32	38	-	TA	KCL	10	PE	NR
Angel (42)	US	1999	RCS	1993–1998	-	16	24	23	TA	KCL	NR	GH	NR
Belogolovkin (43)	US	2007	CCS	2000– 005	-	36	243	-	TA	KCL	10–14	PE	NR
Boulot (44)	France	1993	PCS	1985–1991	32	-	-	48	TV/TA	Aspiration/KCL	8–14	PE	NR
Groutz (45)	Israël	1996	PCS	NR	30	-	30	-	TV	NaCl	10	GH	NR
Haas (46)	Israël	2014	PCS	2005–2011	55	77	78	-	TV	Aspiration	6–8	HDP	NR
Herlihy (47)	US	2017	RCS	2005–2016	42	-	693	43	TA	KCL	12–16	PE	NR
Hwang (48)	Taiwan	2001	RCS	1992–2000	-	54	406	-	TA	KCL	9–12	GH	^a
Jiang (49)	China	2020	RCS	2010–2019	139	-	149	-	TA	KCL	12–25	HDP	NR
Kadhel (50)	France	1998	RCS	1993–1996	17	-	-	24	TA	KCL	9–11	GH	^b
Kim (40)	Korea	2019	RCS	2006–2018		212	157	-	TV/TA	Aspiration/KCL	6–8/11–17	HDP	NR
Lee (51)	Korea	2022	RCS	2006–2018	327	-	-	225	TV/TA	Aspiration/KCL	8–10/10–14	PE	^c
Lipitz (52)	Israël	1994	PCS	1984–1992	31	-	-	84	TA	KCL	9	GH	NR
Lipitz (53)	Israël	1996	RCS	1989–1993	43	-	134	-	TA	KCL	9	GH	NR
Liu (54)	China	2022	RCS	2015–2020	141	-	-	41	TV	Aspiration	6–8	GH	NR
Macones (55)	US	1993	RCS	1988–1992	47	-	63	14	TA	KCL	9–12	HDP	NR
Mostajeran (56)	Iran	2006	PCS	2003–2005	-	30	30	-	TA	KCL	10–13	GH	NR
Nevo (57)	Israël	2003	CCS	1989–1997	-	64	64	-	TV/TA	Aspiration/KCL	7–8/9–11	PE	NR
Okyay (58)	Turkey	2014	RCS	2003–2012	43	-	233	65	TA	KCL	11–14	PE	^d
Porreco (59)	US	1991	PCS	1991	13	-	-	11	TA	KCL	10–11	GH	NR
Raval (60)	US	2015	RCS	1999–2009	30	-	-	102	TA	KCL	10–14	PE	NR
Razaz (61)	Canada	2017	RCS	2009–2013		45	3340	40	NR	NR	NR	GH	NR
Selam (62)	US	1999	RCS	1986–1997	49	77	140	-	TA	KCL	10–13	GH	^e
Seo (63)	Korea	2003	RCS	1995–2002	-	43	264	-	TV	KCL	6–9	PE	NR
Silver (64)	US	1997	CCS	1990–1994	-	18	108	-	TA	KCL	13	PE	NR
Singh (65)	India	2021	PCS	2018–2020	-	64	100	-	TA	KCL	11–13	HDP	NR
Sivan (66)	Israël	2002	RCS	1994–1998	85	-	-	103	TA	KCL	10–14	PE	^f
Smith-Levitin (67)	US	1996	RCS	1990–1994	-	59	88	54	TA	KCL	10–12	PE	NR
Wang (68)	China	2016	RCS	2002–2012	-	130	140	-	TA	KCL	12–25	HDP	NR
Yuce (69)	Turkey	2016	RCS	2007–2014	-	49	282	-	TA	KCL	10–13	PE	NR

ACOG, American College of Obstetricians and Gynecologists; CCS, case-control study; GA, gestational age; GH, gestational hypertension; HDP, hypertensive disorders of pregnancy; KCL, potassium chloride; MFPR, multifetal pregnancy reduction; n, number; NR, not reported; PCS, prospective cohort study; PE, preeclampsia; RCS, retrospective cohort study; US, United States; SD, standard deviation; TA, transabdominal; TV, transvaginal.

^aAccording to standard criteria of the American College of Obstetricians and Gynecologists (ACOG) (74); ^bSystolic pressure >140 mmHg and/or diastolic pressure >90 mmHg; ^cHigh blood pressure (≥140/90 mmHg) and one or more of the following complications after 20 weeks of pregnancy: proteinuria (≥300 mg/24 h, or urine protein: creatinine ratio ≥ 0.3, or dipstick 1+ persistently), thrombocytopenia (platelet count < 100 000/μL), renal insufficiency (creatinine level >1.1 mg/dL or doubling of baseline), impaired liver function, new onset of headaches or visual disturbances; ^dHypertension (systolic blood pressure ≥140 mmHg after 24 weeks gestation) plus proteinuria (urine protein concentration ≥300 mg in a 24-h urine sample) (75); ^eBlood pressure ≥ 140/90 mmHg on two occasions within a 6-hour interval or an increase of >30 mmHg systolic or >15 mmHg diastolic above the first-trimester blood pressure; ^fBlood pressure ≥ 140/90 mmHg on two occasions within a 6-hour interval or an increase of >30 mmHg systolic or >15 mmHg diastolic above the first-trimester blood pressure, with proteinuria >300 mg/24 h or weight gain > 5 lb in ≤1 week, as defined by the ACOG criteria (74).

Table 3. Demographic baseline characteristics of all the included studies.

First author	Study groups	Maternal age in years; mean ± SD	Conception methods, %	Nulliparous, % or mean ± SD
Alexander (41)	MFPR ≥3→2, ongoing twin	30.6 vs. 31.2 (p = 0.498) (SD = NR)	Spontaneous, OI, IVF, GIFT	75 vs. 75 (p = NS)
Angel (42)	MFPR ≥3→2, ongoing twin, ongoing triplet	32.3 ± 0.3 vs. 32.7 ± 1.0 vs. 32.0 ± 0.9 (p = NS)	Spontaneous, OI, IVF, GIFT	84 vs. 46 vs. 84 (p = NS)
Belogolovkin (43)	MFPR ≥3→2, ongoing twin	36.7 ± 4.7 vs. 33.2 ± 6.3 (p = 0.002)	ART (97 vs. 56; p < 0.0001)	25 vs. 29 (p = 0.47)
Boulot (44)	MFPR 3→2, ongoing triplet	32.6 ± 4 vs. 30.4 ± 3.7 (p = 0.13)	Spontaneous (8.3 vs. 0), OI (1.4 vs. 15.6), IVF (79.2 vs. 81.3), GIFT (2.1 vs. 0)	84.4 vs. 85.4 (p = NS)
Groutz (45)	MFPR 3→2, ongoing twin	31.8 ± 4.6 vs. 30.9 ± 3.9 (p = NR)	Spontaneous (0 vs. 100), OI or ART (100 vs. 0)	60 vs. 60 (p = NS)
Haas (46)	MFPR 3→2, MFPR ≥ 3→2, ongoing twin	35.1 ± 6.1 vs. 31.7 ± 4.2 (p < 0.01)^a; 33.6 vs. 31.7 ± 4.2 (p = 0.02)^b	Spontaneous, OI, IVF, egg donation	0.49 vs. 0.52 (p = NS)^b
Herlihy (47)	MFPR 3→2, ongoing twin, ongoing triplet	36.3 ± 4.2 vs. 34.4 ± 6.5 vs. 29.7 ± 5.5 (p < 0.001)	Spontaneous, IVF (69 vs. 66.2 vs. 51.2; p = 0.116)	73.8 vs. 62.3 vs. 44.2 (p = 0.016)
Hwang (48)	MFPR ≥3→2, ongoing twin	32.0 ± 3.6 vs. 29.0 ± 4.4 (p < 0.01)	Spontaneous (0 vs. 47; p < 0.01), OI (7 vs. 39; p < 0.01), IVF (92 vs. 14; p < 0.01)	NR
Jiang (49)	MFPR 3→2, ongoing twin	NR	NR	NR
Kadhel (50)	MFPR 3→2, ongoing triplet	31.7 ± 5.8 vs. 30.8 ± 4.2 (p = NS)	Spontaneous, ART (100 vs. 75)	82.3 vs. 58.3 (p = NS)
Kim (40)	MFPR ≥3→2, ongoing twin	33.0 ± 3.5^c vs. 32.5 ± 3.7^d vs. 33.9 ± 3.0 (p = 0.011)	IUI (10.5c vs. 10.2d vs. 12.7; p = 0.778), IVF/ICSI (89.5c vs. 89.8d vs. 86.6; p = 0.673)	86.3 vs. 84.7 vs. 9.4 (p = 0.392)
Lee (51)	MFPR 3→2, ongoing triplet	33.6 ± 3.9 vs. 33.2 ± 3.4 (p = 0.064)	Spontaneous (3.7 vs. 4.0), OI (15 vs. 41.8), IVF (81.3 vs. 54.2) (p < 0.001)	85.6 vs. 85.8 (p = 0.532)
Lipitz (52)	MFPR 3→2, ongoing triplet	27 ± 5 vs. 28 ± 6 (p = NS)	Spontaneous (2.9 vs. 6.6), OI (47 vs. 67.8), IVF (50 vs. 25.4; p < .01)	73.5 vs. 6.3 (p = NS)
Lipitz (53)	MFPR 3→2, ongoing twin	27 ± 5.1 vs. 27 ± 6.0 (p = NS)	Spontaneous (0 vs. 4.2; p < 0.001), OI (46.5 vs. 36.6), IVF (53.5 vs. 23.2)	69.7 vs. 64.1 (p = NS)
Liu (54)	MFPR 3→2, ongoing triplet	30.3 ± 4.4 vs. 29.2 ± 4.4 (p = NS)^e; 32.2 ± 4.6 vs. 32.0 ± 3.5 (p = NS)^f	IVF/ICSI	NR
Macones (55)	MFPR 3→2, ongoing twin, ongoing triplet	32.2 ± 3.0 vs. 29 ± 5.2 vs. 30 ± 5.1 (p = NS)	NR	0.5 vs. 0.9 vs. 0.6 (p = NS)
Mostajeran (56)	MFPR ≥3→2, ongoing twin	NR	IVF/ICSI	NR
Nevo (57)	MFPR ≥3→2, ongoing twin	NR	Spontaneous (1.6 vs. 67.2; p = sign.), OI (39.1 vs. 1.9; p = sign.), IVF (59.4 vs. 21.9; p = sign.)	NR
Okyay (58)	MFPR 3→2, ongoing twin, ongoing triplet	29.6 ± 4.8 vs 30.1 ± 5.3 vs 28.9 ± 4.5 (p = NS)	OI (0 vs. 9.9 vs. 6.2), IVF (100 vs. 9.1 vs. 93.8; p = 0.103)	93 vs. 81.5 vs. 83.1 (p = NS)
Porreco (59)	MFPR 3→2, ongoing triplet	NR	OI (15.4 vs. 72.7), IVF (61.5 vs. 27.3), GIFT (23.1 vs. 0)	NR
Raval (60)	MFPR 3→2, ongoing triplet	34 ± 4.1 vs. 32.5 ± 4.3 (p = 0.094)	Spontaneous, IVF (100 vs. 67.6; p = 0.002)	1.13 vs. 1.23 (p = 0.755)
Razaz (61)	MFPR ≥3→2, ongoing twin, ongoing triplet	Categorized (n; %) <35 (37.8 vs. 63.6 vs. 57), 35–39 (44.4 vs. 26.9 vs. 30), ≥40 (17.8 vs. 9.6 vs. 12.5)	Spontaneous, ART (88.9 vs. 35.5 vs. 65.0)	66.7 vs. 51.8 vs. 65 (p = NS)
Selam (62)	MFPR 3→2, MFPR ≥ 3→2, ongoing twin	36.1 ± 5.6 vs. 34.7 ± 5.4 vs. 33.8 ± 5.5 (p = NS)	Spontaneous, infertility treatment including IVF (63.3 vs. 59.7 vs. 31.4; p = sign.)	71.4 vs. 71.4 vs. 62.9 (p = NS)
Seo (63)	MFPR ≥3→2, ongoing twin	30.1 ± 3.1 vs. 28.4 ± 4.0 (p = NS)	Spontaneous (0 vs. 100), ART (100 vs. 0)	NR
Silver (64)	MFPR ≥3→2, ongoing twin	32.4 ± 3.2 vs. 30.2 ± 4.9^g vs. 34.4 ± 4.9^h (p = NR)	OI (17 vs. 0 vs. 56), IVF (17vs. 0 vs. 24), GIFT (66 vs. 0 vs. 20) (p = 0.01)	50 vs. 33 vs. 20 (p = NR)
Singh (65)	MFPR ≥3→2, ongoing twin	37.0 ± 6.8 v. 32.5 ± 4.2 (p < 0.001)	Spontaneous (9.4 vs. 25), OI (15.6 vs. 11.0), IVF (75 vs. 64) (p = 0.146)	.18±.41 vs. .22 ± .55 (p < .001)
Sivan (66)	MFPR 3→2, ongoing triplet	29.3 vs. 29.2 (p = 0.9) (SD = NR)	Spontaneous, OI (37.6 vs. 39.8; p = 0.9), IVF (61.2 vs. 54.4; p = 0.4)	1.5±.7 vs. 1.6 ± 1.1 (p = 0.8)
Smith-Levitin (67)	MFPR ≥3→2, ongoing twin, ongoing triplet	NR	IVF (89.3 vs. 97.6 vs. 87), other ART	75.9 vs. 82.7 vs. 84 (p = NS)
Wang (68)	MFPR ≥3→2, ongoing twin	NR	ART	NR
Yuce (69)	MFPR ≥3→2, ongoing twin	33.1 ± 2.4 vs. 31.1 ± 6.1^i vs. 29.6 ± 5.2^j (p = 0.008)	Spontaneous (NR vs. 100 vs 0), IVF (NR vs. 0 vs. 100)	0.16 ± 0–1 vs. 0.56 ± 0–3 vs. 0.05 ± 0–1 (p < 0.001)

ART, assisted reproductive technology; GIFT, gamete intrafallopian transfer; ICSI, intracytoplasmic sperm injection; IVF, in vitro fertilization; MFPR, multifetal pregnancy reduction; NR, not reported; NS, not significant; OI, ovulation induction; SD, standard deviation; sign., significant; vs., versus; yrs, years.

^aMFPR 3→2 versus ongoing twin; ^bMFPR ≥3→2 versus ongoing twin; ^cEarly transvaginal embryo reduction (ER); ^dLate transvaginal fetal reduction (FR); ^eDCTA reduction to twin versus DCTA-expectant management^fTCTA reduction to twin versus TCTA-expectant management; ^gSpontaneously conceived twins; ^hTwins conceived through infertility therapy; ⁱSpontaneously conceived twins; ^jIVF conceived twins.

Figure 2. HDP after MFPR from triplet to twin pregnancy versus ongoing triplet pregnancies.

Figure 3. HDP after MFPR from all higher-order to twin pregnancy versus ongoing triplet pregnancies.

Table 4. Other maternal outcomes.

Comparison/study	GDM; n (%)	CD; n (%)	PPH; n (%)	Placental abruption; n (%)	HELLP; n (%)	Pulm. embolism; n (%)
MFPR 3→2 vs. ongoing triplet
Boulot (43)	NR	10/38 (26) vs. 44/45 (98) (p = NR)	0/32 (0) vs. 1/48 (2) (p = NR)	NR	0/32 (0) vs. 1/48 (2) (p = NR)	0/32 (0) vs. 2/48 (4) (p = NR)
Herlihy (46)	4/42 (10) vs. 6/43 (14) (aOR 0.58 (0.11–3.00))	29/42 (69) vs. 37/43 (86) (aOR 0.25 (0.06–0.94))	3/42 (7) vs. 1/43 (2) (aOR 2.62 (0.20–21.3))^a	NR	NR	NR
Kadhel (49)	NR	4/17 (24) vs. 17/24 (71) (p < 0.01)	NR	NR	NR	NR
Lee (50)	11/327 (3) vs. 14/225 (6) (aOR 0.48 (0.20–1.12; p = 0.1))	NR	15/327 (5) vs. 5/225 (2) (aOR 1.84 (0.63–5.36; p = 0.261))	NR	NR	NR
Lipitz (1994) (51)	NR	18/31 (58) vs. 78/84 (93) (p < 0.001)	NR	NR	NR	NR
Liu (53)^b	3/16 (19) vs. 4/24 (17) (p = NR)	NR	NR	NR	NR	NR
Liu (53)^c	5/125 (4) vs. 3/17 (18) (p = NR)	NR	NR	NR	NR	NR
Macones (54)	1/45 (2) vs. 0/14 (0) (p = NS)	NR	NR	NR	NR	NR
Okyay (57)	2/43 (5) vs. 6/65 (9) (p = NS)	36/43 (84) vs. 58/65 (89) (p = NR)	NR	0/43 (0) vs. 1/65 (2) (p = NS)	NR	NR
Porreco (58)	1/13 (8) vs. 0/11 (0) (p = NR)	8/13 (62) vs. 11/11 (100) (p = NR)	NR	1/13 (8) vs. 0/11 (0) (p = NR)	NR	NR
Raval (59)	1/30 (3) vs. 23/102 (23) (p = 0.015)	NR	NR	0/30 (0) vs. 2/102 (2) (p = 1.0)	NR	NR
Sivan (65)	5/85 (6) vs. 23/103 (22) (p = 0.003)	59/85 (69) vs. 89/103 (86) (p < 0.001)	NR	NR	NR	NR
MFPR ≥3→2 vs. ongoing triplet
Angel (41)	1/16 (6) vs. 3/23 (13) (p = NS)	NR	NR	NR	NR	NR
Razaz (60)	13/45 (29) vs. 8/40 (20) (p = NR)	31/45 (69) vs. 35/40 (88) (p = NR)	NR	NR	NR	NR
Smith-Levitin (66)	3/59 (5) vs. 4/54 (7) (p = NS)	NR	NR	NR	NR	NR
MFPR 3→2 vs. ongoing twin
Groutz (44)	Incidence of GDM similar between groups	21/30 (70) vs. 17/30 (57) (p = NS)	NR	NR	NR	NR
Haas (45)	8/55 (15) vs. 11/78 (14) (p = NS)	NR	NR	NR	NR	NR
Herlihy (46)	4/42 (10) vs. 64/693 (9) (aOR 0.92 (0.31–2.67))	29/42 (69) vs. 433/693 (62) (aOR 1.10 (0.54–2.16))	3/42 (7) vs. 34/693 (5) (aOR 1.43 (0.42–4.90))^a	NR	NR	NR
Jiang (48)	4/139 (3) vs. 3/149 (2) (p = 0.425)	NR	NR	NR	NR	NR
Lipitz (1996) (52)	NR	25/43 (58) vs. 65/134 (49) (RR 1.20 (0.88–1.63))	NR	NR	NR	NR
Macones (54)	1/47 (2) vs. 1/63 (2) (p = NS)	NR	NR	NR	NR	NR
Okyay (57)	2/43 (5) vs. 16/233 (7) (p = NS)	36/43 (84) vs. 137/233 (59) (p < 0.001)	NR	0/43 (0) vs. 2/233 (1) (p = NS)	NR	NR
Selam (61)	NR	34/49 (69) vs. 73/140 (52) (p < 0.05)	1/49 (2) vs. 4/140 (3) (p = NS)	3/49 (6) vs. 2/140 (1) (p = NS)	NR	NR
MFPR ≥3→2 vs. ongoing twin
Alexander (40)	2/32 (6) vs. 4/38 (11) (p = NR)	23/32 (71) vs. 30/38 (79) (p = 0.376)	NR	NR	NR	NR
Angel (41)	1/16 (6) vs. 2/24 (8) (p = NS)	NR	NR	NR	NR	NR
Belogolovkin (42)	2/36 (6) vs. 24/243 (10) (p = 0.40)	NR	NR	0/34 (0) vs 6/192 (3) (p = NS)	NR	NR
Haas (45)	11/77 (14) vs. 11/78 (14) (p = NS)	NR	NR	NR	NR	NR
Hwang (47)	NR	NR	NR	NR	NR	NR
Kim (39)^d	10/153 (7) vs 22/157 (14) (OR 2.33 (1.06–5.10; p = 0.034))	NR	NR	NR	NR	NR
Kim (39)^e	5/59 (8) vs. 22/157 (14) (p = NS)	NR	NR	NR	NR	NR
Mostajeran (55)	NR	NR	NR	2/30 (7) vs. 2/30 (7) (p > 0.05)	NR	NR
Nevo (56)	5/64 (8) vs. 1/64 (2) (p = NS)	41/64 (64) vs. 40/64 (63) (p = NS)	NR	NR	NR	NR
Razaz (60)	13/45 (29) vs. 458/3340 (14) (p = NR)	31/45 (69) vs. 2341/3340 (70) (p = NR)	NR	NR	NR	NR
Selam (61)	NR	51/77 (66) vs. 73/140 (52) (p < 0.05)	1/77 (1) vs. 4/140 (3) (p = NS)	3/77 (4) vs. 2/140 (1) (p = NS)	NR	NR
Seo (62)	3/43 (7) vs. 4/264 (2) (p = 0.022)	NR	NR	NR	NR	NR
Silver (63)^f	1/18 (6) vs. 2/54 (4) (p = NR)	6/18 (33) vs. 20/54 (37) (p = NR)	NR	2/18 (11) vs. 2/54 (4) (p = NR)	NR	NR
Silver (63)^g	1/18 (6) vs. 1/54 (2) (p = NR)	6/18 (33) vs. 23/54 (43) (p = 0.54)	NR	2/18 (11) vs. 2/54 (4) (p = NR)	NR	NR
Singh (64)	NR	55/64 (86) vs. 89/100 (89) (p = 0.568)	NR	NR	NR	NR
Smith-Levitin (66)	3/59 (5) vs. 8/88 (9) (p = NS)	NR	NR	NR	NR	NR
Wang (67)	4/130 (3) vs. 3/140 (2) (p = 0.417)	NR	NR	NR	NR	NR
Yuce (68)^h	NR	43/49 (88) vs. 96/117 (82) (p = 0.403)	NR	NR	0/49 (0) vs. 3/117 (3) (p = 0.258)	NR
Yuce (68)^i	NR	43/49 (88) vs. 159/165 (97) (p = 0.150)	NR	NR	0/49 (0) vs. 0/165 (0)	NR

aOR, adjusted odds ratio; CD, cesarean delivery; GDM, gestational diabetes; HELLP, hemolysis, elevated liver enzymes, low platelets; PPH, postpartum hemorrhage; MFPR, multifetal pregnancy reduction; n, number; NR, not reported; NS, not significant; pulm., pulmonary; vs., versus.

^aDefined as transfusion; ^bDCTA reduction to twin versus DCTA-expectant management; ^cTCTA reduction to twin versus TCTA-expectant management; ^dEarly transvaginal embryo reduction (ER) versus ongoing twin pregnancy; ^eLate transvaginal fetal reduction (FR) versus ongoing twin pregnancy; ^fMFPR ≥3→2 vs. spontaneously conceived twins; ^gMFPR ≥3→2 vs. twins conceived through infertility therapy; ^hMFPR ≥3→2 vs. spontaneously conceived; ⁱMFPR ≥3→2 vs. IVF conceived twins.

Brown MA, Magee LA, Kenny LC, et al. Hypertensive disorders of pregnancy: iSSHP classification, diagnosis, and management recommendations for International Practice. Hypertension. 2018 Jul;72(1):24–43.

 PubMed Web of Science ®Google Scholar

Quintanilla Rodriguez BS, Mahdy H. Gestational diabetes. StatPearls. Treasure Island (FL): StatPearls publishing copyright © 2023. Tampa, FL, USA: StatPearls Publishing LLC; 2023.

 Google Scholar

James AH. Iron deficiency anemia in pregnancy. Obstet Gynecol. 2021 Oct 1;138(4):663–674. doi:10.1097/AOG.0000000000004559.

 PubMed Web of Science ®Google Scholar

Practice Bulletin No. 183: postpartum Hemorrhage. Obstet Gynecol. 2017 Oct;130(4):e168–e186. doi: 10.1097/AOG.0000000000002351

 PubMed Web of Science ®Google Scholar

Schmidt P, Skelly CL, Raines DA. Placental abruption. StatPearls. Treasure Island (FL): StatPearls Publishing Copyright © 2023. Tampa, FL, USA: StatPearls Publishing LLC; 2023.

 Google Scholar

Togioka BM, Tonismae T. Uterine Rupture. StatPearls. Treasure Island (FL): StatPearls Publishing Copyright © 2023. Tampa, FL, USA: StatPearls Publishing LLC; 2023.

 Google Scholar

Kirkpatrick CA. The HELLP syndrome. Acta Clin Belg. 2010; Mar;65(2):91–97. doi: 10.1179/acb.2010.020

 PubMed Web of Science ®Google Scholar

Magley M, Hinson MR, Eclampsia. StatPearls. Treasure Island (FL): StatPearls Publishing Copyright © 2023. Tampa, FL, USA: StatPearls Publishing LLC; 2023.

 Google Scholar

Haftel A, Chowdhury YS. Amniotic Fluid Embolism. StatPearls. Treasure Island (FL): StatPearls Publishing Copyright © 2023. Tampa, FL, USA: StatPearls Publishing LLC; 2023.

 Google Scholar

Alexander JM, Hammond KR, Steinkampf MP. Multifetal reduction of high-order multiple pregnancy: comparison of obstetrical outcome with nonreduced twin gestations. Fertil Steril. 1995; Dec;64(6):1201–1203. doi: 10.1016/S0015-0282(16)57985-0

 PubMed Web of Science ®Google Scholar

Angel JL, Kalter CS, Morales WJ, et al. Aggressive perinatal care for high-order multiple gestations: does good perinatal outcome justify aggressive assisted reproductive techniques? Am J Obstet Gynecol. 1999 Aug;181(2):253–259.

 PubMed Web of Science ®Google Scholar

Belogolovkin V, Ferrara L, Moshier E, et al. Differences in fetal growth, discordancy, and placental pathology in reduced versus nonreduced twins. Am J Perinatol. 2007 Nov;24(10):575–579.

 PubMed Web of Science ®Google Scholar

Boulot P, Hedon B, Pelliccia G, et al. Effects of selective reduction in triplet gestation: a comparative study of 80 cases managed with or without this procedure. Fertil Sterility. 1993 1993 Sep 1;60(3):497–503. doi:10.1016/s0015-0282(16)56167-6.

 PubMed Web of Science ®Google Scholar

Groutz A, Yovel I, Amit A, et al. Pregnancy outcome after multifetal pregnancy reduction to twins compared with spontaneously conceived twins. Hum Reprod. 1996 Jun;11(6):1334–1336.

 PubMed Web of Science ®Google Scholar

Haas J, Hourvitz A, Dor J, et al. Perinatal outcome of twin pregnancies after early transvaginal multifetal pregnancy reduction. Fertil Steril. 2014 May;101(5):1344–1348.

 PubMed Web of Science ®Google Scholar

Herlihy N, Naqvi M, Romero J, et al. Multifetal Pregnancy reduction of trichorionic triplet gestations: what is the benefit? Am J Perinatol. 2017 Dec;34(14):1417–1423.

 PubMed Web of Science ®Google Scholar

Hwang JL, Pan HS, Huang LW, et al. Comparison of the outcomes of primary twin pregnancies and twin pregnancies following fetal reduction. Arch Gynecol Obstet. 2002 Dec;267(2):60–63.

 PubMedGoogle Scholar

Jiang J-J, Han T, Zhu Y-H. The early second-trimester multifetal pregnancy reduction improves pregnancy outcome. CEOG. 2021 2021 Feb 15;48(1):164–167.

 Web of Science ®Google Scholar

Kadhel P, Olivennes F, Fernandez H, et al. Are there still obstetric and perinatal benefits for selective embryo reduction of triplet pregnancies? Hum Reprod. 1998 Dec;13(12):3555–3559.

 PubMed Web of Science ®Google Scholar

Kim MS, Kang S, Na ED, et al. Obstetrical outcomes of embryo reduction and fetal reduction compared to non-reduced twin pregnancies. Arch Gynecol Obstet. 2019 Apr;299(4):953–960.

 PubMed Web of Science ®Google Scholar

Lee JY, Lee SM, Jeong M, et al. Short-term and long-term outcomes of trichorionic triplet pregnancies with expectant management. Acta Obstet Gynecol Scand. 2022 Jan;101(1):111–118.

 PubMed Web of Science ®Google Scholar

Lipitz S, Reichman B, Uval J, et al. A prospective comparison of the outcome of triplet pregnancies managed expectantly or by multifetal reduction to twins. Am J Obstet Gynecol. 1994 Mar;170(3):874–879.

 PubMed Web of Science ®Google Scholar

Lipitz S, Uval J, Achiron R, et al. Outcome of twin pregnancies reduced from triplets compared with nonreduced twin gestations. Obstet Gynecol. 1996 Apr;87(4):511–514.

 PubMed Web of Science ®Google Scholar

Liu S, Li G, Wang C, et al. Pregnancy and obstetric outcomes of dichorionic and trichorionic triamniotic triplet pregnancy with multifetal pregnancy reduction: a retrospective analysis study. BMC Pregnancy Childbirth. 2022 Apr 5;22(1):280. doi: 10.1186/s12884-022-04617-y

 PubMed Web of Science ®Google Scholar

Macones GA, Schemmer G, Pritts E, et al. Multifetal reduction of triplets to twins improves perinatal outcome. Am J Obstet Gynecol. 1993 Oct;169(4):982–986.

 PubMed Web of Science ®Google Scholar

Mostajeran F, Gharavi H, Ahmadi SM. Comparison of twin pregnancy outcome after assisted reproductive technology with and without embryo reduction [Original Article]. Int J Reprod BioMed. 2006;4(2):69–72.

 Google Scholar

Nevo O, Avisar E, Tamir A, et al. Neonatal course and outcome of twins from reduced multifetal pregnancy versus non-reduced twins. Isr Med Assoc J. 2003 Apr;5(4):245–248.

 PubMed Web of Science ®Google Scholar

Okyay E, Altunyurt S, Soysal D, et al. A comparative study of obstetric outcomes in electively or spontaneously reduced triplet pregnancies. Arch Gynecol Obstet. 2014 Jul;290(1):177–184.

 PubMed Web of Science ®Google Scholar

Porreco RP, Burke MS, Hendrix ML. Multifetal reduction of triplets and pregnancy outcome. Obstet Gynecol. 1991 Sep;78(3 Pt 1):335–339.

 PubMed Web of Science ®Google Scholar

Raval DB, Naglak M, Iqbal SN, et al. Outcomes of Triplets reduced to Twins versus non-reduced Triplet Pregnancies. J Clin Gynecol Obstet. 2015;4(1):160–163. doi: 10.14740/jcgo322w

 PubMedGoogle Scholar

Razaz N, Avitan T, Ting J, et al. Perinatal outcomes in multifetal pregnancy following fetal reduction. CMAJ. 2017 May 8;189(18):E652–E658. doi: 10.1503/cmaj.160722

 PubMed Web of Science ®Google Scholar

Selam B, Lembet A, Stone J, et al. Pregnancy complications and neonatal outcomes in multifetal pregnancies reduced to twins compared with nonreduced twin pregnancies. Am J Perinatol. 1999;16(2):65–71. doi: 10.1055/s-2007-993838

 PubMed Web of Science ®Google Scholar

Seo SS, Jo MY, Kim MR, et al. Outcome of twin pregnancies after selective fetal reduction. Korean J Fertil Sterility. 2003;30(1):85–94.

 Google Scholar

Silver RK, Helfand BT, Russell TL, et al. Multifetal reduction increases the risk of preterm delivery and fetal growth restriction in twins: a case-control study. Fertil Steril. 1997 Jan;67(1):30–33.

 PubMed Web of Science ®Google Scholar

Singh C, Thakur S, Shahnaz G, et al. Clinical outcomes in higher-order multiples reduced to dichorionic diamniotic (DCDA) twins compared with primary twins and singletons: a prospective observational study. Int J Gynaecol Obstet. 2022 Jun;157(3):671–676.

 PubMed Web of Science ®Google Scholar

Sivan E, Maman E, Homko CJ, et al. Impact of fetal reduction on the incidence of gestational diabetes. Obstet Gynecol. 2002 Jan;99(1):91–94.

 PubMed Web of Science ®Google Scholar

Smith-Levitin M, Kowalik A, Birnholz J, et al. Selective reduction of multifetal pregnancies to twins improves outcome over nonreduced triplet gestations. Am J Obstet Gynecol. 1996 Oct;175(4 Pt 1):878–882.

 PubMed Web of Science ®Google Scholar

Wang Y. Study on fetal reduction in multiple births. Int J Clin Exp Med. 2016;91:6846–6849.

 Google Scholar

Yuce T. Reduction of multifetal gestation to twins: is it always possible to attain natural outcomes? Cukurova Med J. 2016;41(3): 485–490.

 Google Scholar

ACOG practice bulletin. Diagnosis and management of preeclampsia and eclampsia. Number 33, January 2002. American College of Obstetricians and Gynecologists. Int J Gynaecol Obstet. 2002 Apr;77(1):67–75.

 PubMed Web of Science ®Google Scholar

Brown MA, Lindheimer MD, de Swiet M, et al. The classification and diagnosis of the hypertensive disorders of pregnancy: statement from the International Society for the Study of Hypertension in Pregnancy (ISSHP). Hypertens Pregnancy. 2001;20(1):IX–XIV. doi: 10.3109/10641950109152635

 PubMed Web of Science ®Google Scholar

Review Manager (RevMan) 5.4. The Cochrane Collaboration; 2020.

 Google Scholar