Postpartum Weight : A Guide for Calculation of the Expected Prepregnancy Weight to Study the Risk of Maternal Overweight and Obesity on Congenital Anomalies

Objectives: To study the risk of maternal overweight and obesity on congenital anomalies (CAs) using the 
 expected prepregnancy body mass index (EPPBMI) calculated from the postpartum weight. 
Methods: By deciding four difference factors, one for low, normal, overweight, and obese mothers as 60% of the 
 pregnancy weight gain, then subtracting each factor from the corresponding postpartum weight to calculate the 
 EPPBMI, to study the risk of overweight and obesity on CAs, applied retrospectively on mothers examined in the 
 birth defect center of Al-Ramadi city, Iraq. For every mother delivered CA-affected baby, two mothers delivered 
 healthy neonates were selected randomly as controls. Calculated EPPBMI of the cases compared with controls to 
 study the risk of maternal obesity on CAs using the Odd's ratio and 95% confidence interval as a measure of the risk 
 significance. 
Results: Enrolled mothers were 184 delivered 184 CA-affected neonates, 115 male and 69 female. Mother's age 
 was 16-44 years (mean 28.3 years), their postpartum weight was 52-108 kg (mean 74.6 kg). Both postpartum BMI 
 and EPPBMI in cases showed higher overweight and obesity than in controls. Obesity and overweight found risk 
 factors for studied CAs. Obesity found a risk factor for development of VSD, ASD, congenital hip dislocation, 
 hydrocephalus, meningomyelocele, lip & palate defects, and down's syndrome, while overweight found a risk factor 
 for ASD. 
Conclusion: EPPBMI calculation from the postpartum weight is easy and will make the study of the risk of 
 maternal obesity on CAs simple, especially in areas with poor antenatal care. Overweight and obesity found risk 
 factors for certain CAs. Social education about the early antenatal care and control of obesity before pregnancy are 
 important to reduce the prevalence of CAs.


Introduction
Maternal obesity during pregnancy is a definite risk factor for certain congenital anomalies.
The crude measure of the body fat is the body mass index (BMI).
The WHO classified BMI in to four major groups: About 30-40% of the causes of obesity are genetic and the rest are environmental factors as the high energy foods and sedentary lifestyle.
Obesity during pregnancy increase maternal incidence of gestational diabetes, hypertension, preeclampsia, thromboembolic disorders, cesarean section, and wound infections.
For the baby, it increase his incidence of macrosomia, birth injuries, perinatal death, stillbirth, preterm birth, and congenital anomalies (CAs).
Future childhood obesity increase up to 40% if one parent is obese and to 70% if both are affected.
It has been shown that women who are overweight or obese in the start of the pregnancy has more maternal and child health complications, and the more she is overweight, the more she is and her baby is likely to develop health complications.
If a mother is overweight and planned to be a pregnant, starting weight loss before pregnancy can help to reduce her complications and CAs.
Maternal obesity cause CAs by: -Increase her liability for gestational diabetes that shares with obesity a similar teratogenic metabolic abnormalities like insulin resistance and hyperglycemia.
-The Increase liability to folate deficiency due to the increased metabolic requirements.
-The chronic hypoxia and hypercapnia of obesity which are considered fetal teratogens.
-The increased size of the baby will increase the mechanical forces in the uterine cavity causing different malformations such as the club foot or congenital hip dislocation.
-The increased difficulty of ultrasound examination specially the soft tissue anomalies resulting in a fewer prenatal diagnosis and less terminations of pregnancy.
To study the risk of maternal overweight and obesity on CAs, maternal BMI at conception and maximum up to 10 weeks of pregnancy must be used.
During our study of the risk factors of CAs in Al-Ramadi birth defects center in 2010, we found the vast majority of mothers after delivery didn't know their weight during pregnancy, and studying the relation of obesity with CAs was impossible.
The aim of this study is to use the postpartum weight to calculate the expected prepregnancy weight and BMI, to study the risk of maternal overweight and obesity on CAs, applied retrospectively on patients examined in 2010 in the birth defect center of Al-Ramadi Maternity and Children's Teaching Hospital (MCTH), western Iraq.

Methods
This is a retrospective hospital based case-control study applied from the 1 st of February to the 1 st of October 2015 Mother's data includes her age, height, residence, postpartum weight, and date of examination.
Baby's data include his weight, gender, gestational age, and type of associated structural CAs.
For every mother with CA-affected neonate, two age-matched mothers who delivered sex-matched CA-free neonates were selected randomly as controls.
According to the Institute of Medicine Recommendations, mothers at full term pregnancy will gain an average total pregnancy weight according to their prepregnancy BMI as follows: - The average percent of these reports is 39.7%.
Accordingly, the average retained excess weight of the pregnancy components (breast, uterus, fat, fluid and blood volumes) will be: 100 -39.7 = 60.3%.
This 60.3% is the difference between the maternal weight after delivery and her expected prepregnancy weight (the difference factor).
After delivery, the mother will gradually lose this weight with a maximum weight loss of 0.5 kg/week during the first 6 weeks after delivery, then decreased gradually and takes about 6 to 12 months to reach about her original prepregnancy weight.
When the 60.3 % is applied on mothers of different BMI types according to the Institute of Medicine Recommendations as 60.3% of the corresponding pregnancy gain of weight, the types of the difference factors will be: -Underweight mother = 7.5 kg ± 2.52.
These difference factors are used on the non individual basis.
The expected prepregnancy weight = maternal weight after delivery − corresponding difference factor.
In this study, all mothers were examined at 7-14 days after delivery.
The average weight loss in this period will be 750 g.So; Maternal weight at delivery = postpartum weight + 750 g.
The expected prepregnancy weight = the maternal weight at delivery (or at 7-14 days + 750g) − corresponding difference factor.
EPPBMI of cases is compared with controls to study the risk of obesity on the development of CAs.

Results
Number of enrolled mothers were 184, delivered 184 CA-affected neonates.
Number of controls were 368 mothers delivered 368 sex matched healthy neonates.
Affected neonates composed of 115 males and 69 females.
Because of the multiple CAs, the total different anomalies were 232 and exceeded the number of affected neonates.
Table (1) The changing profile in the cases and controls from the postpartum BMI to the EPPBMI after subtraction of the difference factor.
In the cases, the percent of overweight and obesity in the postpartum BMI was 85.7%, dropped down to 72.3% as EPPBMI.
In the control, the percent in the postpartum BMI was 69.2%, dropped down to 35.8% as EPPBMI.
Higher overweight and obesity values of postpartum BMI and calculated EPPBMI in the cases than controls, Distribution of values toward the upper level of overweight postpartum levels, making them less dropped to a down level as EPPBMI after subtraction of the difference factor than in controls.Both overweight and obese mothers found risk factors significantly associated with the development of CAs, while no relation was found between underweight mothers and CAs.Obesity found a risk factor associated with the development of VSD, ASD, congenital hip dislocation, hydrocephalus, meningomyelocele, down's syndrome and all cleft lip and cleft palates, while overweight found associated with the development of ASD only

Discussion
In areas with high social health education, family medicine system and prepregnancy health care systems, mothers usually started their antenatal care visits early, and the access to mothers before, at, or near conception is easy, and a large number of pregnant mothers can be collected early in pregnancy for prospective, or retrospective studies.
Areas with no family doctor system, no prepregnancy care systems, and low social health education, the first antenatal care may be late or absent, and the medical records will be poor, and collection of adequate number of mothers in this stage will be difficult.The problem in our population is the difficulty to find an adequate number of mothers who expose their early pregnancy because of the social or other factors, and the majority of mothers in our populations didn't know their prepregnancy weight when examined after delivery.
Accordingly, the number of mothers seen near conception is very limited and studying the relation of BMI types with congenital anomalies is difficult.
In other countries specially western countries such problem is less available, and the access for mothers in the prepregnancy stage is easier.
Postpartum weight is easier to access and more practical, and when a multicenter method is used in high delivery rate hospitals or health centers, large number of mothers can be collected in short period, and a uniform perfect well-adjusted weight, height, and BMI measures will result in a rapid, easy and practical method, to study the risk of obesity on CAs.
In this study, the calculation of the EPPBMI involves in addition to the excess weight of the retained pregnancy components, the weight of the excessive fat gain secondary to excessive food intake which may give a false high overestimated results in some of the calculated EPPBMI.
Food intake and weight gain during pregnancy must be limited according to the prepregnancy weight.
Studies showed that the increased appetite and excessive fat gain during pregnancy occurred mostly in those who are already overweight or obese before conception than in those who are underweight or normal weight mothers.This may reduce the overestimation effect of this study since underweight and normal mothers are less liable for excessive weight gain and so will be less overestimated during the calculation of the EPPBMI.
And when overweight mother has additional fat gain and estimated as obese EPPBMI, or an obese mother has additional fat gain and estimated as excessive obesity EPPBMI, this may minimally affect the net result, since both these types are risk factors for CAs.
In this study, the calculated difference factor is 60.3% of all maternal BMI types.For a more precise calculation, the percent must be different according to the types of maternal BMI.
In spite of the extensive review of literatures in this study, we couldn't find any record of neither the percent of the conception products nor the percent of the retained pregnancy components according to the BMI types.
Studies that depended on maternal self-record or recording the BMI at the first 10 weeks of pregnancy may carry a weight difference possibly not less than what we expect in this study.

Conclusion
Calculation of the EPPBMI from the postpartum weight is easy and practical, and useful in areas with poor social health education and antenatal care.
Overweight and obesity is a risk factor for the development of CAs.

Recommendations
To prove the accuracy of this method, another prospective study is required to follow up four groups of BMI types mothers from conception till delivery, and calculate the total pregnancy weight gain, the weight of the conception products, and the difference factors of each type, and our method will be accurate if the difference factor was equal or near to the 60% of the pregnancy weight gain according to the types of prepregnancy BMI.

Table ( 3
) Recorded CAs according to the types of BMI (EPPBMI).

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Obese mothers associated with 41% of the CAs, overweight mothers with 32.3%, normal mothers with 26.3%, and less than 1% with underweight mothers

Table ( 2
) The risk of EPPBMI types on the development of CAs.

Table ( 4
) The risk of EPPBMI types on the most common recorded CAs.