Childbirth and Perinatal Outcomes of Healthy, Low-risk Pregnant Women With Abnormal Total Gestational Weight Gain.

doi:10.21203/rs.3.rs-1435383/v1

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Research Article

Childbirth and Perinatal Outcomes of Healthy, Low-risk Pregnant Women With Abnormal Total Gestational Weight Gain.

https://doi.org/10.21203/rs.3.rs-1435383/v1

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Purpose

Little is known on the potential effects of abnormal GWG among low-risk, healthy pregnant women with no comorbidities or gestational complications.

We investigated perinatal outcomes of these pregnancies according to GWG as per the 2009 National Academy of Medicine (NAM) recommendations.

Methods

A retrospective analysis of prospectively collected data of low-risk pregnant women giving birth after 37^0/7weeks’ gestation at our center between 1/2016 and 12/2020. Only women with normal pregestational BMI (pBMI) (18.5-24.9 Kg/m²) and no pre- or gestational complications were included. Self-reported prepregnancy weight was used to calculate pBMI; GWG was the difference between maternal weight at childbirth and prepregnancy weight. Women were classified according to the 2009 NAM guidelines for GWG: insufficient (iGWG, <11.5 Kg), adequate (aGWG, 11.5-16 Kg), and excessive (eGWG, >16 Kg). Logistic regression analysis with aGWG as referent was performed to independent estimate dose-response associations.

Results

During the study period, there were 4,127 (33.1%) births fulfilling the inclusion criteria. Fifty-two percent of women gained outside the recommended range: 33.5% had iGWG and 18.7% eGWG. iGWG women were 40% more likely to have early-term births and SGA neonates. In turn, eGWG women displayed increased odds of prolonged pregnancy (aOR 1.32), cesarean section in labor (aOR 1.50), high-degree perineal tears (aOR 2.04, postpartum hemorrhage >1000 mL (aOR 1.54), and LGA newborns (aOR 1.83).

Conclusion

Our data show that abnormal GWG can independently associate with heightened risk of adverse outcomes among healthy, low-risk pregnant women with normal pBMI and no comorbidities or gestational complications.

Gestational weight gain

low-risk

childbirth

outcomes

Total gestational weight gain (GWG) is the total amount of weight a pregnant woman gains between the time of conception and the onset of labor. [1]

The first recommendations on GWG were published in 1990 by the National Academy of Medicine (NAM), and subsequently updated in 2009 with inclusion of specific GWG ranges according to prepregnancy Body Mass Index (pBMI). [1, 2] These recommendations mostly aimed to optimize fetal growth. However, several studies have subsequently shown negative effects of weight gain outside NAM ranges on relevant perinatal outcomes other than altered fetal growth, including hypertensive disorders of pregnancy, birth by cesarean section (CS), and preterm labor, thus providing observational validation of the updated recommendations. [3–5] In addition, adverse effects on woman’s and offspring long-term health have been identified for weight gain above guidelines, by increasing the risk for obesity and chronic comorbidities. [6] Nonetheless, adequate GWG has been consistently reported to occur only in a small fraction of pregnancies. [7]

Mounting attention has been focused lately on optimization of GWG in the context of obesity, maternal chronic diseases, gestational complications, and twin pregnancies, in the attempt to finely balance competing maternal and fetal needs. [8–14]

In turn, the effects of abnormal GWG on perinatal outcomes among healthy, low-risk singleton pregnant women with no chronic or gestational conditions has been much less investigated. [15–18] The scarce available evidence has also limitations due to inclusion of overweight and obese low-risk women, who are known to have increased odds of adverse outcomes compared to normal pBMI women. [15, 16, 18, 19] Furthermore, studies on the topic have lacked to report additional relevant childbirth outcomes other than fetal growth and mode of birth, such as high degree perineal tears and postpartum hemorrhage (PPH) [3–6], which can both contribute to substantial short- and long-term morbidity for women. [20, 21]

Therefore, the purpose of the current study was to investigate the effects of abnormal total GWG on several relevant childbirth and perinatal outcomes among a well-characterized cohort of healthy, low-risk singleton pregnant women at term, with normal pBMI, and no chronic conditions or gestational complications.

We hypothesized that women with inadequate or excessive total GWG would be at increased risk of adverse outcomes other than altered fetal growth and CS, thus possibly providing useful novel knowledge for local practice and management guidelines.

This is a retrospective analysis of prospectively collected data of all low-risk singleton pregnant women giving birth after 37^0/7 weeks’ gestation at our center between January 1st, 2016 and December 31st, 2020.

In line with regional dispositions where the research site is located, low-risk pregnant women are supervised by midwives throughout the antenatal, intrapartum, and postnatal period, with referral to obstetrician-led care if complications arise. [22, 23]

Only women fulfilling the regional criteria for being low-risk both during pregnancy and at the time of Labor & Birth (L&B) unit admission for childbirth were included in the present analyses. [22, 23] The exclusion criteria were: multiple gestation, maternal age < 18 or ≥ 45 years, chronic maternal pregestational conditions, gestational maternal or fetal complications, abnormal placental location and placenta accreta spectrum, history of PPH, manual removal of the placenta, uterine surgery, or other known antenatal risk factors for PPH, preterm labor < 37 weeks’ gestation, breech presentation at L&B unit admission, first antenatal assessment ≥ 14 weeks, and abnormal pBMI (< 18.5 Kg/m², 25-29.9 Kg/m², ≥ 30 Kg/m²).

pBMI was calculated as self-reported prepregnancy weight (Kg) divided by square of height (m) measured without shoes and light clothing at the first prenatal visit < 14 weeks. Self-reported pregestational weight was compared with weight assessed at the first antenatal evaluation. Since pregnant women are assumed to gain 0.5–2 Kg during the first trimester, [1] patients with > 2 Kg difference between self-reported pregestational weight and clinician measured weight at first visit were excluded due to reliability concerns for accurate pBMI categorization.

Total GWG was defined as the difference in kilograms between weight measured on the day of L&B unit admission and self-reported prepregnancy weight. [10, 24] NAM recommends a weight gain of 11.5–16 Kg for normal pBMI women. Weight gain below, within, and above these ranges was classified as insufficient (iGWG), adequate (aGWG), and excessive (eGWG), respectively. [1]

Data on pregnancy course and outcomes were reviewed (S.O., S.F., S.G., A.M.O., V.B., and L.L.) and registered in a dedicated log book, which was periodically audited (S.O., S.F., A.N., and P.V.) before data analysis was performed. Informed consent for participation in the study and for publication of deidentified data was obtained from all women included. The study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Institutional Review Board of the University of Milan-Bicocca, Italy (protocol No. 106, October 14th 2015).

Outcome measures

We assessed several relevant childbirth and perinatal outcomes, including early, late, and post term childbirth, mode of birth, high degree perineal tears, PPH, and birth of a small for gestational age (SGA) or large for gestational age (LGA) neonate.

Early term childbirth was defined as giving birth between 37^0/7 and 38^6/7 gestational weeks, late term between 41^0/7 and 41^6/7 weeks, and post term at > 41^6/7 weeks. [25] Gestational age at birth was calculated based on the first trimester ultrasound scan report. [26]

High degree perineal tears included 3rd and 4th degree lacerations. Specifically, 3rd degree tears were diagnosed as those extending into the capsule and muscle of the rectal sphincter, whereas 4th degree tears as those involving the rectal mucosa. [20]

PPH was defined as a quantified blood loss at childbirth of ≥ 1000 mL. [27] Quantification of blood loss was performed with the use of graduated collection bags and visual aids at vaginal birth, [28] and of suction bottles and weighted surgical pads at CS. According to the Italian guidelines on PPH prevention and treatment, [21] all women giving birth vaginally at our center receive 10 IU of oxytocin intramuscularly at the time of fetal anterior shoulder birth for PPH prophylaxis. If an increased PPH risk is identified (i.e., prolonged second stage of labor, vacuum birth, retained placenta), women will also receive 20 IU of oxytocin intravenously (in 250 mL of saline at 125 mL/h). In turn, women undergoing CS receive 5 IU of oxytocin intravenously (in 100 mL of saline at 1200 mL/h), followed by 20 IU of oxytocin.

SGA and LGA neonates were defined as those with birthweight < 10th or > 90th percentile for gestational age, respectively, according to Italian reference charts, which account for parity and fetal gender. [29]

Statistical analyses

Assessment of normality was performed by means of Kolmogorov–Smirnov test. Statistical analyses included Chi-Square test or Fischer Exact test for categorical variables, and independent Student’s T-test and One-way ANOVA for continuous variables. A logistic regression model with adequate GWG group as referent and adjusted for potential confounding variables was employed to estimate dose-response associations with childbirth and perinatal outcomes of interest, which were expressed as adjusted odds ratios (aORs) and 95% CIs.

Statistical significance was set at P < .05 (SPSS software, version 25; Prism software, version 7).

During the study period, there were 12,487 births at our Institution. Among these, 4,127 (33.1%) were from healthy, low-risk, uncomplicated singleton pregnant women at term with a normal pBMI. Figure 1 displays the number of women for each exclusion criterion, leading to the final study population.

Mean age was 32 years and 51.7% of women were at their first pregnancy (Table 1).

Table 1

Demographic and phenotypic characteristics of study population.
Variables	Study population N = 4127	iGWG n = 1384 (33.5)	aGWG n = 1970 (47.7)	eGWG n = 773 (18.8)	p-value	iGWG vs aGWG	eGWG vs aGWG
Maternal age (years) - > 35 - > 40	32.0 ± 5.0 1003 (24.3) 162 (3.9)	32.0 ± 5.1 338 (24.4) 55 (4.0)	32.3 ± 4.8 507 (25.7) 80 (4.1)	31.3 ± 5.2 158 (20.4) 27 (3.5)	< 0.001 0.014 0.783	0.061 0.396 0.929	< 0.001 0.003 0.584
Caucasian ethnicity	3646 (88.3)	1171 (84.6)	1790 (90.9)	685 (88.6)	< 0.001	< 0.001	0.086
Pregestational BMI (Kg/m²)	21.4 ± 1.7	21.4 ± 1.7	21.3 ± 1.7	21.4 ± 1.7	0.009	0.005	0.027
Total GWG (Kg)	13.2 ± 4.2	8.8 ± 2.4	13.8 ± 1.4	19.3 ± 2.6	< 0.001	< 0.001	< 0.001
ART	50 (2.0)	13 (1.6)	24 (2.0)	13 (2.7)	0.349	0.505	0.360
First pregnancy	2135 (51.7)	668 (48.3)	1042 (52.9)	425 (55.0)	0.004	0.009	0.328
Multiparity ≥ 3	120 (2.9)	53 (3.8)	49 (2.5)	18 (2.3)	0.042	0.032	0.891
GWG, gestational weight gain; iGWG, inadequate GWG (< 11.5 Kg); aGWG, adequate GWG; eGWG, excessive GWG (> 16 Kg); BMI, body mass index; ART, assisted reproductive technology.

The overall total GWG was 13.2 ± 4.2 Kg; more than half of women (n = 2157, 52.3%) did not achieve the recommended gain according to the 2009 NAM guidelines, with 1,384 (33.5%) women having iGWG and 773 (18.7%) eGWG. There were no women with weight loss, but 26 (1.9%) gained no weight throughout gestation. Among eGWG cases, 388 (50.2%) had a gain of 0.5-2 Kg above the upper limit of the NAM range, i.e., 16 Kg, whereas 28 (3.6%) gained ≥ 10 Kg above such limit.

Distribution of BMI at birth and contribution of total GWG to each BMI at birth group is shown in Fig. 2 (A and B). Women with BMI at birth ≥ 30 Kg/m² were more frequently represented in the eGWG group compared to the other groups (27.3% versus 3.2% in aGWG versus 0% in iGWG, p < 0.001).

Women with eGWG were more likely to give birth after 41 weeks’ gestation, whereas iGWG pregnancies had higher odds of an early term birth compared to aGWG (Table 2).

Table 2

Labor, childbirth, and perinatal outcomes of study population.
Variables	Study population N = 4127	iGWG n = 1384 (33.5)	aGWG n = 1970 (47.7)	eGWG n = 773 (18.8)	p-value	iGWG vs aGWG	eGWG vs aGWG
GA at birth - Early term - Late/post term	39.5 ± 1.1 727 (17.6) 851 (20.6)	39.4 ± 1.1 305 (22.0) 234 (16.9)	39.6 ± 1.1 326 (16.5) 421 (21.4)	40.0 ± 1.1 96 (12.4) 196 (25.4)	< 0.001 < 0.001 < 0.001	< 0.001 < 0.001 0.011	0.004 0.007 0.027
Induction of labor - For late/post term	535 (10.2) 165 (30.8)	141 (10.2) 29 (20.6)	269 (13.7) 94 (34.9)	125 (16.2) 42 (33.6)	< 0.001 0.008	0.003 0.003	0.102 0.821
Epidural analgesia	903 (22.0)	248 (18.0)	446 (22.7)	209 (27.1)	< 0.001	< 0.001	0.017
Oxytocin in labor	635 (15.4)	172 (12.4)	316 (16.0)	147 (19.0)	< 0.001	0.004	0.070
Prolonged 2nd stage of labor	130 (3.3)	42 (3.1)	62 (3.3)	26 (3.6)	0.840	0.840	0.716
Spontaneous VB	3775 (91.5)	1295 (93.6)	1802 (91.5)	678 (87.7)	< 0.001	0.025	0.003
Vacuum VB	139 (3.4)	35 (2.5)	70 (3.6)	34 (4.4)	0.057	0.107	0.317
In labor CS	197 (4.8)	48 (3.5)	91 (4.6)	58 (7.5)	< 0.001	0.113	0.004
Episiotomy	407 (10.8)	126 (9.7)	202 (11.2)	79 (11.7)	0.306	0.193	0.776
3rd -4th degree perineal tears	51 (1.2)	16 (1.2)	18 (1.0)	17 (2.2)	0.296	0.601	0.010
Manual removal of placenta	110 (2.8)	28 (2.1)	58 (3.1)	24 (3.4)	0.149	0.096	0.708
Blood loss at delivery (mL) - ≥ 1000 - ≥ 1500	343.6 ± 249.2 131 (3.2) 23 (0.6)	321.1 ± 224.8 37 (2.7) 5 (0.4)	349.6 ± 254.9 58 (2.9) 13 (0.7)	368.7 ± 272.1 36 (4.7) 5 (0.6)	< 0.001 0.030 0.485	< 0.001 0.674 0.338	0.084 0.035 1.000
2nd line uterotonic drugs	201 (4.9)	54 (3.9)	92 (4.7)	55 (7.1)	0.020	0.112	0.035
Additional procedures to control PPH	42 (1.0)	9 (0.7)	23 (1.2)	10 (1.3)	0.237	0.150	0.846
Blood transfusions	13 (0.3)	3 (0.2)	6 (0.3)	4 (0.5)	0.486	0.744	0.482
Female neonate	2008 (48.7)	709 (51.2)	943 (47.9)	356 (46.1)	0.054	0.058	0.396
Birthweight centile - < 10th - > 90th	297 (7.2) 327 (7.9)	128 (9.2) 78 (5.6)	132 (6.7) 147 (7.5)	37 (4.8) 102 (13.2)	< 0.001 < 0.001	0.007 0.042	0.064 < 0.001
Apgar score at 5 min < 7	8 (0.2)	1 (0.1)	6 (0.3)	1 (0.1)	0.291	0.251	0.681
GWG, gestational weight gain; iGWG, inadequate GWG (< 11.5 Kg); aGWG, adequate GWG; eGWG, excessive GWG (> 16 Kg); BMI, body mass index; GA, gestational age; NR FHR, non-reassuring fetal heart rate; VB, vaginal birth; CS, cesarean section; CP, cephalopelvic; PPH, postpartum hemorrhage.
Early term: 37^0/7 – 38^6/7 weeks of gestation; full term: 39^0/7 – 40^6/7 weeks of gestation; late term: 41^0/7 – 41^6/7 weeks of gestation; post term: ≥42^0/7
Epidural analgesia: only among women with labor (n = 4111/4127, 99.6%).
Prolonged duration of 2nd stage of labor defined according to the 2018 WHO guidelines: >3 hours in nulliparous women, > 2 hours in multiparous women.
Episiotomy and 3rd -4th degree perineal tears: only among women with spontaneous vaginal birth.
Manual removal of placenta was calculated only among women with vaginal birth.
Clinically significant PPH defined as quantified blood loss ≥ 1000 mL or any blood loss accompanied by signs of hypovolemia and requiring blood transfusions.
2nd line uterotonic drugs include methylergometrine (i.m), sulprostone (i.v), carboprost tromethamine (i.m), misoprostol (rectal), tranexamic acid (i.v.)
Additional procedures to control PPH include uterine massage, uterine tamponade by balloon, D&C, pelvic artery embolization, uterine or vascular ligatures, hysterectomy.
Birthweight centile defined according to Italian population charts (Ines charts).

Epidural analgesia was requested during labor by 22% of women, with progressively increasing rates according to GWG group (18% in iGWG versus 22.7% in aGWG versus 27.1% in eGWG, p < 0.001). In turn, rates of spontaneous vaginal birth showed a progressive reduction with increasing GWG: 93.6% in iGWG versus 91.5% in aGWG versus 87.7% in eGWG (p < 0.001). Women with eGWG displayed increased frequency of cesarean birth (7.9% versus 5.0% in aGWG, p = 0.005), specifically related to CS in labor. There were no differences between eGWG and aGWG regarding rates of labor induction, oxytocin use, and prolonged second stage of labor.

Among women with spontaneous vaginal birth (n = 3,775), high degree perineal tears more commonly occurred in eGWG versus aGWG group (1.0% versus 2.2%, p = 0.010). In addition, women with eGWG were more likely to experience PPH ≥ 1000 mL and to require the use of 2nd line uterotonic drugs.

Rates of LGA progressively increased according to GWG, with eGWG women showing the highest rate. In turn, SGA neonates were more frequently observed among women with inadequate gain compared to the other groups (9.2% versus 6.7% in aGWG versus 4.8% in eGWG, p < 0.001).

There were no cases of stillbirth or early neonatal death.

A logistic regression model adjusted for potential confounding factors with aGWG group as referent confirmed all the findings of the univariate analysis, except for a higher likelihood of spontaneous vaginal birth in women with iGWG. (Table 3).

Table 3

Logistic regression model of childbirth and perinatal outcomes of interest.
Variables	aGWG	eGWG
		OR	95% CI	aOR	95% CI
Late and post term ¹	Ref.	1.225	1.002–1.497	1.320	1.013–1.492
CS in labor ²	Ref.	1.675	1.192–2.354	1.503	1.063–2.126
3rd and 4th degree perineal tears ⁴	Ref.	2.291	1.283–4.082	2.042	1.115–3.756
PPH ≥ 1000 mL ³	Ref.	1.611	1.053–2.462	1.539	1.046–2.365
BW centile > 90th ⁵	Ref.	1.885	1.443–2.464	1.830	1.398–2.395
		iGWG
Early term ⁶	Ref.	1.425	1.198–1.696	1.403	1.177–1.672
Spontaneous VB ⁷	Ref.	1.357	1.039–1.771	1.209	0.911–1.607
BW centile < 10th ⁸	Ref.	1.419	1.101–1.828	1.456	1.128–1.881
GDM, gestational diabetes mellitus; PTB, preterm birth, CS, caesarean section.
¹ Adjusted for maternal age > 35 years, pregestational BMI.
² Adjusted for maternal age > 35 years, pregestational BMI, late & post term, epidural analgesia, birthweight centile > 90th .
³ Adjusted for maternal age > 35 years, pregestational BMI, late & post term, epidural analgesia, CS in labor, 3rd -4th degree perineal tears, birthweight centile > 90th .
⁴ Adjusted for maternal age > 35 years, pregestational BMI, epidural analgesia, birthweight centile > 90th .
⁵ Adjusted for maternal age > 35 years, pregestational BMI, late & post term.
⁶ Adjusted for Caucasian ethnicity, first pregnancy, pregestational BMI.
⁷ Adjusted for Caucasian ethnicity, first pregnancy, pregestational BMI, early term, epidural analgesia, oxytocin in labor.
⁸ Adjusted for Caucasian ethnicity, first pregnancy, pregestational BMI, early term.

Absolute rate increase values were also calculated, with eGWG leading to 4, 2.9, 1.8, 1.2, and 5.7 more cases per 100 births of late and post term birth, CS in labor, PPH, 3rd and 4th degree perineal tears, and LGA neonates, respectively. Regarding women with iGWG, we observed an absolute rate increase of 5.5 and 2.5 per 100 births for early term birth and SGA neonate, respectively.

Here we show that among a well-characterized cohort of healthy, low-risk singleton pregnant women at term, more than half do not achieve optimal weight gain during pregnancy and that such abnormal GWG associated with higher odds of adverse childbirth and perinatal outcomes. Specifically, women with iGWG were more likely to give birth in the early term time-window and to an SGA neonate. In turn, women who gained more weight than recommended more commonly experienced prolonged pregnancy, CS in labor, high degree perineal tears, PPH ≥ 1000 mL, and LGA newborns.

Although the importance of appropriate GWG is well established worldwide, many women still gain either to little or too much weight during gestation.

A recent systematic review and meta-analysis on the topic has reported gain outside NAM ranges for 70% of pregnant women, with 23% gaining below and 47% above [3]. Similarly, in our cohort we observed 52.3% of women not achieving adequate GWG. However, insufficient weight gain occurred more frequently than excessive gain (33.5% versus 18.8%). This finding could be likely explained by the characteristics of our study population, including only healthy women without comorbidities and a normal pBMI, and it is in line with previously reported data suggesting higher odds of insufficient and excessive gain among normal weight and overweight/obese women, respectively [7, 30].

Women with iGWG in our cohort showed higher rates of early term birth, whereas excessive weight gain associated with increased likelihood of late and post term birth.

The timely onset of labor and delivery is an important determinant of perinatal outcome. Early term births between 37- and 38-weeks’ gestation have been shown to associate with higher neonatal and infant morbidity and mortality compared to full term births. [31] Similarly, increased perinatal morbidity and mortality have been identified as pregnancy extends beyond 41 weeks, thus requiring a more intense antenatal surveillance and use of resources [32]. We did not observe cases of stillbirth or early neonatal death. However, women with eGWG and prolonged pregnancy ≥ 41 weeks underwent increased antenatal surveillance for fetal wellbeing assessment according to our institutional protocol. [33]

We observed unfavorable outcomes related to altered fetal growth of weight gain outside NAM recommendations. Specifically, women gaining insufficient weight gave more commonly birth to an SGA neonate, whereas eGWG women to an LGA newborn. These findings are consistent with previous reports, showing elevated rates of SGA in women with normal pBMI and iGWG, as well as increased odds of LGA for excessive gain across all pBMI categories. [3, 34–36] Considering the potential short- and long-term complications of SGA and LGA, [37–39] prevention of both conditions by promoting adequate GWG might be advisable from an obstetric and public health point of view.

Regarding additional relevant childbirth outcomes, low-risk women who gained more weight than recommended more commonly experienced CS in labor, high degree perineal tears, and PPH ≥ 1000 mL.

While the finding regarding CS is in line with previous works, [3, 40] increased odds of high degree perineal tears and PPH have never been reported before in such a well characterized low-risk obstetric population.

We identified only two studies on genital tract trauma among healthy, low-risk pregnant women with midwife-led care; however, both included overweight and obese women and did not adjust analyses for different pBMI values and LGA rates, [16, 17] known risk factors for perineal trauma. By assessing only healthy women with a normal pBMI and no comorbidities, we did not incur in potential biases related to maternal pregravid weight status and its strong independent effect on perinatal outcomes. [34] Although the overall rate of genital tract trauma was low in our cohort (1.2%), women with eGWG displayed a two-fold risk increase compared to their aGWG counterparts.

As per PPH, we could not find any research work on this outcome in healthy, uncomplicated pregnant women with abnormal GWG. Considering that PPH is a leading cause of maternal morbidity and mortality, [41] our finding of a 1.5-fold increase in the odds of PPH deserves further attention. If confirmed in larger prospective studies, consideration could be given to inclusion of eGWG in PPH risk assessment tools, [21] to increase preparedness in this otherwise low-risk population.

A major strength of this study is that yields new evidence on GWG according to the 2009 NAM recommendations in a large and well-characterized population of healthy, low-risk uncomplicated singleton pregnant women with normal pBMI.

Additional strengths are as follows. Prepregnancy weight and height were recorded in early pregnancy and therefore prospective regarding outcome, thus avoiding recall bias. pBMI was ascertained by using self-reported preconception weight, which has been shown to be more accurate for assessing total GWG as compared to first trimester weight, particularly among women with normal pBMI, [42, 43] and it is recommended by the 2009 NAM guidelines. [1] Also, we excluded women with a > 2 Kg difference between self-reported weight and weight measured at the first antenatal visit < 14 weeks, thus further limiting errors in pBMI categorization. [4, 19, 44] Biases in calculating total GWG were limited by measuring last maternal weight upon admission for childbirth. Institutional protocols to guide supervision of low-risk pregnant women during pregnancy and childbirth are consistently followed at our center, and, as such, a standardized care model is ensured. Finally, consistent definitions of the outcomes of interest, which included a wide range of childbirth and perinatal outcomes, were applied, thus increasing clinical usefulness and comparability.

Our study has some limitations.

First, it was a single-center study, which limit generalizability of our findings and lead to the need of external validation. Second, the retrospective design may have conducted to unrecognized confounding factors. Last, we did not assess the potential impact of abnormal GWG on medium-term outcomes, such as weight retention and rate of breastfeeding at 6 months post-partum. [45]

Although with limitations, our work is the first to focus on the effects of GWG on a wide range of childbirth and perinatal outcomes in a large and well-characterized cohort of healthy, low-risk singleton pregnant women with normal pBMI and no comorbidities. Thus, it has implications for clinical practice and contributes valuable information to the midwives and obstetricians taking care of these women.

Italian and British guidelines on antenatal care for low-risk pregnancies still do not recommend to offer women the opportunity to be weighted at every antenatal visit, unless clinical management can be influenced or nutrition is a concern, in order to avoid maternal anxiety. [22, 46] Yet, longitudinal evaluation of GWG is pivotal for timely identification of deviations and for potentially modifying the total GWG by providing appropriate counseling about eating and physical activity. Importantly, pregnancy is a time when women are more motivated to improve their health behaviors. [47]

Of note, our data suggest that adherence to the 2009 NAM weight gain recommendations can be helpful in reducing risk of adverse outcomes among low-risk pregnant women. Thus, adequate training of clinicians to effectively counsel these women on achieving healthy weight gain targets appears mandatory. [48, 49]

Funding statement

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Competing Interest statement

The authors have no relevant financial or non-financial interests to disclose

Author Contributions

S. Ornaghi: project conceptualization and development, data management, data analysis, manuscript writing, reviewing, and editing.

S. Fumagalli: project development, data management, manuscript editing.

S. Galimberti: data collection, manuscript editing.

AM Ornago: data collection, manuscript editing.

V. Brivio: data collection, manuscript editing.

L. Lambicchi: project development, data collection.

A. Nespoli: project development, manuscript reviewing.

P. Vergani: project development, manuscript reviewing.

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Childbirth and Perinatal Outcomes of Healthy, Low-risk Pregnant Women With Abnormal Total Gestational Weight Gain.

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