Twin pregnancies occur when there are two developing fetus in the uterus at a given time. The chances of conceiving twins, or having a multifetal gestation, has been on an increasing incidence over the last few decades owing to the increased use of artificial reproductive techniques, including in vitro fertilisation, ovulation induction, increased age of the mother at conception that is especially prevalent in the present society. Although the incidence of multifetal gestation, including twin pregnancy, accounts for a lesser percentage of live births, they account for a disproportionately high percentage relative to their incidence for adverse perinatal outcomes and also, increased maternal complications. ^[1]

Multifetal gestation are associated with increased maternal and fetal complication. The major fetal complications associated with twin pregnancy are prematurity, low birth weight, respiratory distress syndrome, birth asphyxia, intra uterine growth retardation, congenital abnormalities, fetal malpresentations, premature rupture of membranes, umbilical cord prolapse, cord entanglement, placenta previa, abruptio placenta, etc. there is increased incidence of maternal complications like spontaneous abortion, anemia, hyperemesis gravidarum, gestational diabetes mellitus, preeclampsia, increased chances of caesarean section, postpartum haemorrhage. ^[2]

Twins are either fraternal or identical.

• Fraternal twins or dizygotic twins comprise of two-thirds of twin pregnancies. Fraternal twins occur when two sperm fertilize two eggs in one cycle. This results in a separate placenta , amnion and chorionic sac. for each fetus. Fraternal twinning depends on the race, age of the mother where it is directy proportional, preconceptional weight. The Yoruba race of Nigeria has high dizygotic twinning rate due to the consumption of a specific type of yam containing natural phytoestrogen which may promote double ovulation.
• Identical twins or monozygotic twins occur when a single embryo from one egg and one sperm divide in two. The twins may share one or have separate placentas. Identical twins are always of the same sex. There are three types of monozygotic twins depending on the timing at which the zygote divides.

The aim of this study is to evaluate the obstetrical factors influencing the morbidity of the second twin in a twin gestation at a tertiary care centre with a study period of 18 months extending between February 2021 and August 2022.

This Hospital based cross sectional, descriptive study was conducted in IPD of Obstetrics and Gynecology Department in Vani Vilas Hospital, BMCRI. Duration of study was February 2021 to August 2022.

Sample size Calculation:

The sample size is calculated based on the prevalence of twin gestation comprising of 3.3% of all pregnancies.¹

n= Z_a² x pq /d2

Where n=sample size

 Z_a=Z value (e.g. 1.96 at 95% confidence interval)

p=prevalence twin gestation= 3.3%

q=(100-p) =96.7%

 d=absolute precision of 5%

Substituting the values above, gives a sample size of 49.03 which is rounded off to 50.

Inclusion Criteria:

1. Patient willing to give informed consent.
2. Women with twin gestation diagnosed clinically and confirmed by ultrasound
3. Women with twin gestation more than 28 weeks of gestation
4. Absence of congenital anomaly in either fetus

Exclusion Criteria:

1. Patient not willing to give informed consent.
2. Women with twin gestation less than 28 week of gestation
3. Women with multifetal gestation other than twin pregnancy
4. Intrauterine deaths of either of the fetus
5. Congenital anomaly in either fetus

Methodology:

After obtaining approval and clearance from the institutional ethics committee, the patients fulfilling the inclusion criteria will be enrolled for the study after obtaining informed consent. The booked cases in the hospital will be followed up in the antenatal clinic. All the emergency admission cases fulfilling the inclusion criteria will also be studied after obtaining informed consent. For all the delivered babies of the study participants, the perinatal outcome will be noted. All relevant information from the case record will be noted including maternal age, gravidity, parity, clinical examination, ultrasound reports, gestational age at birth, presentation of the foetuses, mode of delivery, birth weight, apgar score, need for NICU admission will be noted. The babies will be followed up till discharge. The cause of death will be noted in case of perinatal death.

Outcome Measures:

The perinatal outcome of the second twin will be evaluated with respect to apgar scores at 1 minute and 5 minutes, birth weight, need for NICU admission and perinatal mortality and morbidity and the cause for the same.

The obstetrical factors such as gravidity, gestational age, presentation, mode of delivery, any operative or instrumental intervention required for the delivery of the second twin, inter delivery interval between the first and second twin, chorionicity of the placenta will be noted.

Statistical Analysis:

The collected data will be analyzed by appropriate statistical tests and SPSS software version 20.0. Descriptive statistics of the explanatory and outcome variables will be calculated by mean, standard deviation for quantitative variables, frequency and proportions for qualitative variables. Inferential statistics like Chi-square test will be applied for categorical variables. Outcome of the patients will be analyzed using appropriate parametric and non-parametric test for significant association between the variables. The level of significance is set at 5%. Any other necessary tests found appropriate will be dealt at the time of analysis based on data distribution.

Majority of the women had gestational age between 32 to 36weeks, followed by 29.33% between 37 to 42weeks and 16% between 28 to 32weeks. 70.67% of the women had pre-term delivery.

94.7% of the cases were booked cases and 5.3% were unbooked cases.  42.7 % cases had gravida 1, 40% cases had gravida 2 and 17.3% cases had gravida 3. 42.7% had parity 1 and 5.3% had parity 2.  42.7% had 1 living and 4% had 2 living.  78.7% of the women had history of abortions.

72% had DCDA and 28% had MCDA.

70.7% of the mothers did not have any co-morbidities. 34.7% patients presented in early labour, 20% in active labour, 82.7% of women undergoing LSCS has no indication. 2.7% non-progression of labour, 2.7% leading twin in non-vertex, followed by Non progression of Labour, Non-Vertex Presentation, Unfavourable Cervix, First Twin Transverse lie, Second Twin In transverse lie, Cord Prolapse, Face presentation, Foot Prolapse and Transverse lie.

Perinatal morbidity in twin2 (n=47)

In the present study, pre-term delivery, Chorionicity of DCDA, mode of delivery, APGAR score at 1 minute had significant association with NICU admission of twin 2.

Table no 1: association of perinatal morbidity (NICU admission) with type of pregnancy of twin 2.

Though the booked cases were high in twin 2, there was no statistical association between morbidity and type of pregnancy.

Majority of the twin pregnancy cases were between 35 to 39weeks of gestation. Of whom majority of them were late pre-term cases. This had statistically significant association with the morbidity.

Table no 2: Association of perinatal morbidity (nicu admission) with living

Table no 3: Association of perinatal morbidity (NICU admission) with Gravida

In this study, morbidity of Twin 2 was same irrespective of gravida status.

Morbidity had no association with incidence of abortion in mothers.

Table no 4: Association of perinatal morbidity (NICU admission) with chorionicity

Majority of the twin with NICU admission had chorionicity of DCDA. DCDA had significant association with NICU admission.

Table no 5: Association of perinatal morbidity (NICU admission) with presentation

Majority of the twin with morbidity had breech presentation.

Table no 6: Association of perinatal morbidity (NICU admission) with mode of delivery

Commonest mode of delivery of twins was normal vaginal delivery. Majority with morbidity also belong to vaginal delivery group.

Table no 7: Association of perinatal morbidity (NICU admission) with APGAR at 1 minute.

Majority of the twin 2 with mobidity belonged tp moderate APGAR score at 1 minute. There is significant association with moderate score and morbidity of twin2.

Table no 8: Association of perinatal morbidity (NICU admission) with APGAR at 5 minute

Majority of the twin 2 with morbidity had excellent APGAR score at 5 minute, though not statistically associated.

Table no 9: Association of perinatal morbidity (NICU admission) with Inter-delivery interval

Twin 2 with less inter-delivery period had the greater morbidity rate compared to others, though not statistically significant.

Table no 10: Labour stage at admission and its association with Morbidity.

Stage of labour presentation did not have statistical association with the morbidity of the twin 2.

Discussion: Morbidity is assessed in-terms of ICU admission. In the present study, pre-term delivery, Chorionicity of DCDA, mode of delivery, APGAR score at 1 minute had significant association with NICU admission of twin 2.A study by Joshi R et al[2], there was no correlation between neonatal admission and inter-delivery interval. Similar results of no association was observed in twin 2 and NICU admission. A study by Jariwala KH et al[3], 34% of first twin and 40% of second twin required NICU admission. NICU admission has significant morbidity infants due to reduced maternal bonding and lowering long term breastfeeding rates. Hence NICU admission is considered for morbidity assessment in our study. Pre-term delivery On analysing the neonatal morbidity pre-term delivery was commonest in our study. We found that there is statistically significant association of pre-term and late pre-term delivery in increasing the NICU admission of the neonates. Pre-term delivery irrespective of twin 1 or 3 opposes significant morbidity due to requirement of surfactant, steroids, and antibiotics. Efforts to improve neonatal outcomes must address the rate of pre-term birth, particularly among multiple gestations, which contribute a disproportionate share to the burden of PTB and neonatal morbidity. Morbidity- Chorionicity In the present study, pre-term delivery, Chorionicity of DCDA, mode of delivery, APGAR score at 1 minute and APGAR score at 5minutes had significant association with NICU admission of twin 2. A study by Shrim et al[4] , monochorionic (MC) diamniotic twin pregnancies twins have higher rate of admission to the NICU (55.91% vs. 36.57%, P < 0.001). \ APGAR score at 1 minute A study by Jariwala HK et al[3] , showed higher incidence of APGAR score <7 at 5minutes in twin 2. Our study showed high incidence of moderate APGAR score in twin 2, which showed statistical association with NICU admission.

Twin 2(62.66%) had higher NICU admission rate compared to twin 1(44%). Common reasons for NICU admission was respiratory distress, low birth weight and neonatal jaundice. Perinatal mortality was 4% in twin 1 and 8% in twin 2. Perinatal morbidity of twin 2 was evaluated in comparison with NICU admission. Pre-term delivery, Chorionicity of DCDA, mode of delivery, APGAR score at 1 minute had significant association with NICU admission of twin 2

1. Williams Obstetrics, 25rd edition, eBook version 1.0, Chapter 8, preconceptional care, p 386. 2. Aziz S, Soomro N. Twin births and their complications in women of low socioeconomic profile. J Pak Med Assoc. 2012;62:1204–1208. 3. Martin JA, Hamilton BE, Osterman MJ. Three decades of twin births in the United States, 1980-2009. NCHS Data Brief 2012;80:1-8. 4. 12. NJOG 2015 Jan-Jun; 19 (1):89-93 5. Jariwala, Heny K., et al. "A prospective observational study of foetal outcome in twin pregnancy delivering at a tertiary health care center of South Gujarat." International Journal of Reproduction, Contraception, Obstetrics and Gynecology, vol. 10, no. 3, Mar. 2021, pp. 905. 6. Shrim A, Weisz B, Gindes L, Gagnon R. Parameters associated with outcome in third trimester monochorionic diamniotic twin pregnancies. J ObstetGynaecol Can. 2010 May;32(5):429-434.